In early summer, the bacterium E. coli creates anxiety. After Germany and Sweden, France, in turn, is affected. In Morocco, there are no reported cases but must remain vigilant. In summer, the strict adherence to hygiene is the best prevention.
Monday, June 20, 2011
Friday, June 17, 2011
Thursday, June 16, 2011
VI. Importance of Microorganisms in Foods
Since 1900 A.D., our understanding of importance of microorganisms in food has interested greatly. Their role in food can be either desirable (food bioprocessing) or undesirable (foodborne diseases and food spoilage), which is briefly discussed here.
V. Early Development in Food Microbiology (Prior to 1900 A.D)
It is not known exactly when our ancestors recognized the importance of the invisible creature, now designated as microorganisms, in food. But it had to be around 8000 B.C. in the Near East after they developed agriculture and animal husbandry. They produced more foods than they could consume within the short growing season, and a portion of the produce was lost due to spoilage. They solved the problems and secured uniform food supplies throughout the year by developing different preservation technique. Between 8000 and 2000 B.C., they used drying, cooking, smoking, salting, low temperature, baking, modified atmosphere, fermentation, spices, and honey to extend the storage life of different types of raw and processed foods. Although we are not sure if they had perceptions about the cause of foodborne diseases, they definitely associated food spoilage with some invisible factors and developed successful preventative measure.
From the time of the Greeks until the discovery of biogenesis, spoilage of foods, especially of meat and fish, was thought to be due to spontaneous generation, such as the development of maggots. When the presence of different types of bacteria in many foods was discovered, their appearance through spontaneous generation was explained to be the cause of food spoilage. Schawnn (1837) and Helmholtz (1843) associated the presence of microorganisms (bacteria) in food with both putrefactive and fermentative changes of foods. However, they did not believe in spontaneous generation, but they could not explain how microorganisms could bring about those changes. Finally, Pasteur resolved the mystery by explaining that contamination of foods with microorganisms from environment and their subsequent metabolic activities and growth were the cause of fermentation of grapes, souring of milk, and putrefaction of meat.
Diseases caused by the consumption of certain foods (foodborne disease) was recognized at least during Middle Ages. Ergot poisoning in Europe was related to the consumption of grains (infested with molds) in the 12th century. In 1857, consumption of raw milk was suspected to be cause of typhoid fever. In 1870, Selmi related certain food poisoning with ptomaine (histamine). Gaertner was the forst to isolate Salmonella from a meat implicated in a foodborne diseases in 1888. Denys, in 1894, was able to establish Staphylococcus aureus with food pisioning and, in 1896, Ermengem isolatedClostridium botulinum from food. The association of many other pathogenic bacteria and viruses to foodborne was established after 19900 A.D.
Paseur, in the 1860s, rcognized the role of yeasts in alcohol fermentation. He also sowed that souring of wine was due to growth of acetic acid producing bacteria (Acetobacter aceti), and developed the pasteurization process (heating at 145˚ F for 30 min) to selectively eliminate these undesirable bacteria from wine. Like fermentation, cheese ripening was suggested by Martin in 1867 to be of microbial origin. John Lister, in 1873, was able to isolate milk-suring bacteria (Lactococcus lactis) by the serial dilution (dilution to exctinction) procedure. Cienkowski, in 1878, isolated the bacteria (Leuconostoc mesenteroides) associated with slime formation in sugar (sucrose). In 1895, microbial enumeration of milk was developed by von Geuns. After 1900 A.D., the involvement of different microorganisms in food spoilage and food fermentation was demonstrated.
From the time of the Greeks until the discovery of biogenesis, spoilage of foods, especially of meat and fish, was thought to be due to spontaneous generation, such as the development of maggots. When the presence of different types of bacteria in many foods was discovered, their appearance through spontaneous generation was explained to be the cause of food spoilage. Schawnn (1837) and Helmholtz (1843) associated the presence of microorganisms (bacteria) in food with both putrefactive and fermentative changes of foods. However, they did not believe in spontaneous generation, but they could not explain how microorganisms could bring about those changes. Finally, Pasteur resolved the mystery by explaining that contamination of foods with microorganisms from environment and their subsequent metabolic activities and growth were the cause of fermentation of grapes, souring of milk, and putrefaction of meat.
Diseases caused by the consumption of certain foods (foodborne disease) was recognized at least during Middle Ages. Ergot poisoning in Europe was related to the consumption of grains (infested with molds) in the 12th century. In 1857, consumption of raw milk was suspected to be cause of typhoid fever. In 1870, Selmi related certain food poisoning with ptomaine (histamine). Gaertner was the forst to isolate Salmonella from a meat implicated in a foodborne diseases in 1888. Denys, in 1894, was able to establish Staphylococcus aureus with food pisioning and, in 1896, Ermengem isolatedClostridium botulinum from food. The association of many other pathogenic bacteria and viruses to foodborne was established after 19900 A.D.
Paseur, in the 1860s, rcognized the role of yeasts in alcohol fermentation. He also sowed that souring of wine was due to growth of acetic acid producing bacteria (Acetobacter aceti), and developed the pasteurization process (heating at 145˚ F for 30 min) to selectively eliminate these undesirable bacteria from wine. Like fermentation, cheese ripening was suggested by Martin in 1867 to be of microbial origin. John Lister, in 1873, was able to isolate milk-suring bacteria (Lactococcus lactis) by the serial dilution (dilution to exctinction) procedure. Cienkowski, in 1878, isolated the bacteria (Leuconostoc mesenteroides) associated with slime formation in sugar (sucrose). In 1895, microbial enumeration of milk was developed by von Geuns. After 1900 A.D., the involvement of different microorganisms in food spoilage and food fermentation was demonstrated.
IV. What are They Functions ?
The involvement of invisible organisms in many diseases in human was suspected as early as the 13th century by Roger Bacon. In the 16th century, Francostro of Verona suggested that many human diseases were transmitted by small creatures from person to person. This was also indicated by Kircher in 1658. in 1762, von Plenciz of Vienna suggested that different invisible organisms were responsible for different diseases. Schawnn (1837) and Hermann Helmholtz (1843) pointed out that putrefaction and fermentation were connected with the presence of the organisms derived from air. Finally, Pasteur, in 1875, showed that wine fermentation from grapes and souring of wine were caused by microorganisms. He also proved that spoilage of meat and milk was associated with the growth of microorganisms. Later, he showed the association of microorganisms with several disease in humans, cattle, and sheep, and later developed vaccines against several human and animal diseases, including the rabies virus. Robert Koch, in Germany (in the 1880s and 1890s), isolated bacteria in pure culture responsible for anthrax, cholera, and tuberculosis. He also developed the famous Kohc`s Postulate to associates a specific bacterium as a causative agent for a specific disease. Along with his associates, he also developed techniques of agar planting methods to isolate bacteria in pure cultures, the Petri dish (by Petri in his laboratory), and staining methods for better microscopic observation of bacteria.
With time, the importance of microorganisms in human and animal diseases, soil fertility, plant disease, fermentation, food spoilage and foodborne diseases, and other areas was recognized, and microbiology was developed as a separate discipline. Later, it was divided into several disciplines, such as medical microbiology, soil microbiology, plant pathology, and food microbiology.
With time, the importance of microorganisms in human and animal diseases, soil fertility, plant disease, fermentation, food spoilage and foodborne diseases, and other areas was recognized, and microbiology was developed as a separate discipline. Later, it was divided into several disciplines, such as medical microbiology, soil microbiology, plant pathology, and food microbiology.
III. Where are They Coming From ?
Following Leeuwenhoek`s discovery, although there no bursts of activity, some scientist minds did have the curiosity to determine the animalcules, found to be present in many different object, were coming from. Society had just emerged from Renaissance period and science, known as experimental philosophy, was in its infancy. The theory of spontaneous generations, i.e., the generation of some from of life from nonliving objects, had many strong followers among the educated and elite class. Since the time of the Greeks, the emergence of maggots from dead bodies and spoiled flesh was thought to be due to spontaneous generation. But around 1665, Redi disproved that theory by showing that the maggots in soiled meat and fish could only appear if flies were allowed to contaminate them. The advocates of spontaneous generation theory argued that the animalcules could not regenerate by themselves (biogenesis), but they were present in different things only through abiogenesis (spontaneous generation). In 1749, Needham showed that boiled meat and meat both, following storage in covered flasks, showed the presence of animalcules within a short time. This was used to prove the appearance of these animalcules by spontaneous generation. Spallanzani (1765) showed that boiling meat infusion in broth in a flask and sealing the flask immediately prevented the appearance of these microscopic organisms and thus disproved Needham`s theory. This was the time when Antonie-Laurent Lavoisier and his workers showed the need of oxygen for life. The believers of abiogenesis rejected Spallanzani`s observation, suggesting that there was enough vital force (oxygen) present in sealed flask for animalcules to appear through spontaneous generation. Later, Schulze (1830; by passing air through acid). Theodore schwann (1838; by cotton) showed that bacteria failed to appear in boiled meat infusion even in the presence of air. Finally, in 1864, Louis Pasteur demonstrated that, in boiled infusion, bacteria could grow only if infusions were contaminated with bacteria carried by dust particles in air. His careful and controlled studies proved that bacteria were able to reproduce (biogenesis) and life could not originate by spontaneous generation. John Tyndall, in 1870, showed that in a dust-free box, boiled infusion could be stored in dust-free air without microbial growth.
II. Discovery of Microorganisms
The discovery of microorganisms ran parallel with the invention and improvement of microscope. Around 1658, Athanasius Kircher reported that using a microscope, he had seen minute living worms in putrid meat and milk. The magnification power of his microscope was so low that he cloud not have seen bacteria. In 1664, Robert Hooke described the structure of molds. However, probably the first person to see different types of microorganisms, especially bacteria, was the Dutch businessman turned naturalist Anton Van Leeuwenhoek, using microscope that probably have not above 300x magnification power. He observed bacteria in saliva, rain water, vinegar, and other material, sketched the tree morphological groups (spheroids or cocci, cylindrical or bacilli, and spral or spirillia), and also described some to be motile. He called them animalcules and in 1675 reported his observation to the newly formed leading scientific organization, The Royal Society of London, were his observation were read with fascination. As fairly good microscopes were not easily available at the time, during the course of next 100 years, other interested individuals and scientists only confirmed Leeuwenhoek`s observations. In the 19th century, as result of the Industrial Revolution, improved mind to see and describe creatures they discovered under microscope. By 1838, Ehrenberg (who introduced the term bacteria) had proposed at least 16 species in four genera and by 1875 Cohn had developed the preliminary classification system of bacteria. Cohn also was the first to discover that some bacteria produced spores. Although, like bacteria, the existence of submicroscopic viruses was recognized in the mid-19th century, they were observed only after the invention of electron microscope in the 1940s.
I. Introduction
Except for a few sterile food, all foods harbor one or more types of microorganism. Some of them have desirable role in food, such as in the production of fermented food, while others cause food spoilage and foodborne diseases. To study the role of microorganisms in food and control them when necessary, it is important to isolate them in pure culture and study their characteristics. Some of the most simple technique in use today for studies were developed over the last 300 years; brief description is included here.
Monday, June 6, 2011
Common Foodborne Pathogens
Even though the United States has one of the safest food supplies in the world, there are still millions of cases of foodborne illness each year. Here are common foodborne pathogens (disease-causing microorganisms) with research-based information that includes:
* Cause of illness
* Incubation period
* Symptoms
* Possible contaminants
* Steps for prevention
Bacillus cereus
* Cause of illness: large molecular weight protein (diarrheal type) or highly heat-stable toxin (emetic type)
* Incubation period: 30 minutes to 15 hours
* Symptoms: diarrhea , abdominal cramps, nausea, and vomiting (emetic type)
* Possible contaminants: meats, milk, vegetables, fish, rice, potatoes, pasta, and cheese
* Steps for prevention: pay careful attention to food preparation and cooking guidelines.
Campylobacter jejuni
* Cause of Illness: Infection, even with low numbers
Incubation Period: One to seven days
* Symptoms: Nausea, abdominal cramps, diarrhea, headache - varying in severity
* Possible Contaminant: Raw milk, eggs, poultry, raw beef, cake icing, water
* Steps for Prevention: Pasteurize milk; cook foods properly; prevent cross-contamination.
Clostridium botulinum
* Cause of Illness: Toxin produced by Clostridium botulinum
Incubation Period: 12 to 36 hours
* Symptoms:Nausea, vomiting, diarrhea, fatigue, headache, dry mouth, double vision, muscle paralysis, respiratory failure
* Possible Contaminant: Low-acid canned foods, meats, sausage, fish
* Steps for Prevention: Properly can foods following recommended procedures; cook foods properly.
Clostridium perfringens
* Cause of illness: undercooked meats and gravies
* Incubation period: 8 to 22 hours
* Symptoms: abdominal cramps and diarrhea, some include dehydration
* Possible contaminants: meats and gravies
* Steps for prevention: proper attention to cooking temperatures.
Cryptosporidium parvum
* Cause of Illness: Drinking contaminated water; eating raw or undercooked food; putting something in the mouth that has been contaminated with the stool of an infected person or animal; direct contact with the droppings of infected animals.
* Incubation Period: Two to 10 days
* Symptoms: Watery diarrhea accompanied by mild stomach cramping, nausea, loss of appetite. Symptoms may last 10 to 15 days.
* Possible Contaminants: Contaminated water or milk, person-to-person transmission (especially in child daycare settings). Contaminated food can also cause infections.
* Steps for Prevention: Avoid water or food that may be contaminated; wash hands after using the toilet and before handling food. If you work in a child care center where you change diapers, be sure to wash hands thoroughly with soap and warm water after every diaper change, even if you wear gloves. During communitywide outbreaks caused by contaminated drinking water, boil drinking water for 1 minute to kill the Cryptosporidium parasite. Allow water to cool before drinking it.
Escherichia coli 0157:H7
* Cause of Illness: Strain of enteropathic E.coli
Incubation Period: Two to four days
* Symptoms: Hemorrhagic colitis, possibly hemolytic uremic syndrome
* Possible Contaminant: Ground beef, raw milk
* Steps for Prevention: Thoroughly cook meat; no cross-contamination.
Giardia lamblia
* Cause of Illness: Strain of Giardia lamblia Incubation Period: One to two weeks
* Symptoms: Infection of the small intestine, diarrhea, loose or watery stool, stomach cramps, and lactose intolerance.
* Possible Contaminant: Giardia is found in soil, food, water, or surfaces that have been contaminated with the feces from infected humans or animals..
* Steps for Prevention: Avoid swallowing contaminated recreational water (pools, hot tubs, fountains, lakes, rivers, ponds) or contaminated bathroom fixtures, toys, changing tables, diaper pails; avoid eating uncooked contaminated food; boil water for 1 minute before use or use a water filter with an absolute pore size of at least 1 micron or rated for "cyst removal." Cholorination or iodination of water may be less effective. Avoid fecal exposure during sexual activity
Hepatitis A
* Cause of illness: Hepatitis A Virus (HAV)
* Incubation period:
* Symptoms: fever, malaise, nausea, abdominal discomfort
* Possible contaminants: water, fruits, vegetables, iced drinks, shellfish, and salads
* Steps for prevention: carefully wash hands with soap and water after using a restroom, changing a diaper, and before preparing food.
Listeria monocytogenes
* Cause of Illness: Infection with Listeria monocytogenes
Incubation Period: Two days to three weeks
* Symptoms: Meningitis, sepsticemia, miscarriage
* Possible Contaminant: Vegetables, milk, cheese, meat, seafood
* Steps for Prevention: Purchase pasteurized dairy products; cook foods properly; no cross-contamination; use sanitary practices.
Norwalk, Norwalk-like, or norovirus
* Cause of Illness: Infection with Norwalk virus
Incubation Period: Between 12 and 48 hours (average, 36 hours); duration, 12-60 hours
* Symptoms: Nausea, vomiting, diarrhea and abdominal cramps
* Possible Contaminant: raw oysters/shellfish, water and ice, salads, frosting, person-to-person contact
* Steps for Prevention: Adequate and proper treatment and disposal of sewage, appropriate chlorination of water, restriction of infected food handlers from working with food until they no longer shed virus.
Salmonellosis
* Cause of Illness: Infection with Salmonella species
Incubation Period: 12 to 24 hours
* Symptoms: Nausea, diarrhea, abdominal pain, fever, headache, chills, prostration
* Possible Contaminant: Meat, poultry, egg or milk products
* Steps for Prevention: Cook thoroughly; avoid cross-contamination; use sanitary practices.
Staphylococcus
* Cause of Illness: Toxin produced by certain strains of Staphylococcus aureus
* Incubation Period: One to six hours
Symptoms: Severe vomiting, diarrhea, abdominal cramping
* Possible Contaminant: Custard- or cream-filled baked goods, ham, tongue, poultry, dressing, gravy, eggs, potato salad, cream sauces, sandwich fillings
* Steps for Prevention: Refrigerate foods; use sanitary practices.
Shigella
* Cause of illness: Water contaminated with human feces and unsanitary food handling
* Incubation period: 12 to 50 hours
* Symptoms: abdominal pain, cramps, diarrhea, fever, vomiting, blood, and pus
* Possible contaminants: salads, raw vegetables, dairy products, and poultry
* Steps for prevention: practice proper washing and sanitizing techniques.
Toxoplasma gondii
* Cause of Illness: Parasitic infection
Incubation Period: Five to 23 days after exposure
* Symptoms: In healthy children and adults, toxoplasmosis may cause no symptoms at all, or may cause a mild illness (swollen lymph glands, fever, headache, and muscle aches).
Toxoplasmosis is a very severe infection for unborn babies and for people with immune system problems.
* Possible Contaminant: Cat, rodent or bird feces, raw or undercooked food.
* Steps for Prevention: Wash hands thoroughly after working with soil, cleaning litter boxes, before and after handling foods, and before eating. Cover sandboxes when not in use.
Vibrio
* Cause of illness: excretion of toxin from infected fish and shellfish
* Incubation period: four hours to four days
* Symptoms: diarrhea, abdominal cramps, nausea, vomiting, headache, fever, and chills
* Possible contaminants: fish and shellfish
* Steps for prevention: cook fish and shellfish thoroughly
Yersiniosis
* Cause of Illness: Infection with Yersinia enterocolitica
Incubation Period: One to three days
* Symptoms: Enterocolitis, may mimic acute appendicitis
* Possible Contaminant: Raw milk, chocolate milk, water, pork, other raw meats
* Steps for Prevention: Pasteurize milk; cook foods properly; no cross-contamination; use sanitary practices.
Retail/Institutional Food Service Food Safety and Management
Source : http://www.extension.iastate.edu/foodsafety/pathogens/index.cfm?parent=37
* Cause of illness
* Incubation period
* Symptoms
* Possible contaminants
* Steps for prevention
Bacillus cereus
* Cause of illness: large molecular weight protein (diarrheal type) or highly heat-stable toxin (emetic type)
* Incubation period: 30 minutes to 15 hours
* Symptoms: diarrhea , abdominal cramps, nausea, and vomiting (emetic type)
* Possible contaminants: meats, milk, vegetables, fish, rice, potatoes, pasta, and cheese
* Steps for prevention: pay careful attention to food preparation and cooking guidelines.
Campylobacter jejuni
* Cause of Illness: Infection, even with low numbers
Incubation Period: One to seven days
* Symptoms: Nausea, abdominal cramps, diarrhea, headache - varying in severity
* Possible Contaminant: Raw milk, eggs, poultry, raw beef, cake icing, water
* Steps for Prevention: Pasteurize milk; cook foods properly; prevent cross-contamination.
Clostridium botulinum
* Cause of Illness: Toxin produced by Clostridium botulinum
Incubation Period: 12 to 36 hours
* Symptoms:Nausea, vomiting, diarrhea, fatigue, headache, dry mouth, double vision, muscle paralysis, respiratory failure
* Possible Contaminant: Low-acid canned foods, meats, sausage, fish
* Steps for Prevention: Properly can foods following recommended procedures; cook foods properly.
Clostridium perfringens
* Cause of illness: undercooked meats and gravies
* Incubation period: 8 to 22 hours
* Symptoms: abdominal cramps and diarrhea, some include dehydration
* Possible contaminants: meats and gravies
* Steps for prevention: proper attention to cooking temperatures.
Cryptosporidium parvum
* Cause of Illness: Drinking contaminated water; eating raw or undercooked food; putting something in the mouth that has been contaminated with the stool of an infected person or animal; direct contact with the droppings of infected animals.
* Incubation Period: Two to 10 days
* Symptoms: Watery diarrhea accompanied by mild stomach cramping, nausea, loss of appetite. Symptoms may last 10 to 15 days.
* Possible Contaminants: Contaminated water or milk, person-to-person transmission (especially in child daycare settings). Contaminated food can also cause infections.
* Steps for Prevention: Avoid water or food that may be contaminated; wash hands after using the toilet and before handling food. If you work in a child care center where you change diapers, be sure to wash hands thoroughly with soap and warm water after every diaper change, even if you wear gloves. During communitywide outbreaks caused by contaminated drinking water, boil drinking water for 1 minute to kill the Cryptosporidium parasite. Allow water to cool before drinking it.
Escherichia coli 0157:H7
* Cause of Illness: Strain of enteropathic E.coli
Incubation Period: Two to four days
* Symptoms: Hemorrhagic colitis, possibly hemolytic uremic syndrome
* Possible Contaminant: Ground beef, raw milk
* Steps for Prevention: Thoroughly cook meat; no cross-contamination.
Giardia lamblia
* Cause of Illness: Strain of Giardia lamblia Incubation Period: One to two weeks
* Symptoms: Infection of the small intestine, diarrhea, loose or watery stool, stomach cramps, and lactose intolerance.
* Possible Contaminant: Giardia is found in soil, food, water, or surfaces that have been contaminated with the feces from infected humans or animals..
* Steps for Prevention: Avoid swallowing contaminated recreational water (pools, hot tubs, fountains, lakes, rivers, ponds) or contaminated bathroom fixtures, toys, changing tables, diaper pails; avoid eating uncooked contaminated food; boil water for 1 minute before use or use a water filter with an absolute pore size of at least 1 micron or rated for "cyst removal." Cholorination or iodination of water may be less effective. Avoid fecal exposure during sexual activity
Hepatitis A
* Cause of illness: Hepatitis A Virus (HAV)
* Incubation period:
* Symptoms: fever, malaise, nausea, abdominal discomfort
* Possible contaminants: water, fruits, vegetables, iced drinks, shellfish, and salads
* Steps for prevention: carefully wash hands with soap and water after using a restroom, changing a diaper, and before preparing food.
Listeria monocytogenes
* Cause of Illness: Infection with Listeria monocytogenes
Incubation Period: Two days to three weeks
* Symptoms: Meningitis, sepsticemia, miscarriage
* Possible Contaminant: Vegetables, milk, cheese, meat, seafood
* Steps for Prevention: Purchase pasteurized dairy products; cook foods properly; no cross-contamination; use sanitary practices.
Norwalk, Norwalk-like, or norovirus
* Cause of Illness: Infection with Norwalk virus
Incubation Period: Between 12 and 48 hours (average, 36 hours); duration, 12-60 hours
* Symptoms: Nausea, vomiting, diarrhea and abdominal cramps
* Possible Contaminant: raw oysters/shellfish, water and ice, salads, frosting, person-to-person contact
* Steps for Prevention: Adequate and proper treatment and disposal of sewage, appropriate chlorination of water, restriction of infected food handlers from working with food until they no longer shed virus.
Salmonellosis
* Cause of Illness: Infection with Salmonella species
Incubation Period: 12 to 24 hours
* Symptoms: Nausea, diarrhea, abdominal pain, fever, headache, chills, prostration
* Possible Contaminant: Meat, poultry, egg or milk products
* Steps for Prevention: Cook thoroughly; avoid cross-contamination; use sanitary practices.
Staphylococcus
* Cause of Illness: Toxin produced by certain strains of Staphylococcus aureus
* Incubation Period: One to six hours
Symptoms: Severe vomiting, diarrhea, abdominal cramping
* Possible Contaminant: Custard- or cream-filled baked goods, ham, tongue, poultry, dressing, gravy, eggs, potato salad, cream sauces, sandwich fillings
* Steps for Prevention: Refrigerate foods; use sanitary practices.
Shigella
* Cause of illness: Water contaminated with human feces and unsanitary food handling
* Incubation period: 12 to 50 hours
* Symptoms: abdominal pain, cramps, diarrhea, fever, vomiting, blood, and pus
* Possible contaminants: salads, raw vegetables, dairy products, and poultry
* Steps for prevention: practice proper washing and sanitizing techniques.
Toxoplasma gondii
* Cause of Illness: Parasitic infection
Incubation Period: Five to 23 days after exposure
* Symptoms: In healthy children and adults, toxoplasmosis may cause no symptoms at all, or may cause a mild illness (swollen lymph glands, fever, headache, and muscle aches).
Toxoplasmosis is a very severe infection for unborn babies and for people with immune system problems.
* Possible Contaminant: Cat, rodent or bird feces, raw or undercooked food.
* Steps for Prevention: Wash hands thoroughly after working with soil, cleaning litter boxes, before and after handling foods, and before eating. Cover sandboxes when not in use.
Vibrio
* Cause of illness: excretion of toxin from infected fish and shellfish
* Incubation period: four hours to four days
* Symptoms: diarrhea, abdominal cramps, nausea, vomiting, headache, fever, and chills
* Possible contaminants: fish and shellfish
* Steps for prevention: cook fish and shellfish thoroughly
Yersiniosis
* Cause of Illness: Infection with Yersinia enterocolitica
Incubation Period: One to three days
* Symptoms: Enterocolitis, may mimic acute appendicitis
* Possible Contaminant: Raw milk, chocolate milk, water, pork, other raw meats
* Steps for Prevention: Pasteurize milk; cook foods properly; no cross-contamination; use sanitary practices.
Retail/Institutional Food Service Food Safety and Management
Source : http://www.extension.iastate.edu/foodsafety/pathogens/index.cfm?parent=37
Sunday, June 5, 2011
Human skin harbors completely unknown bacteria
The first study to identify the composition of bacterial populations on the skin using a powerful molecular method. Not only were the bacteria more diverse than previously estimated, but some of them had not been found before,” stated Dr Martin J Blaser, Frederick King Professor and Chair of the Department of Medicine and Professor of Microbiology at New York University (NYU) School of Medicine.
According to Dr Blaser and his team, the skin, the largest organ in the human body, is a kind of zoo and some of the inhabitants are quite novel. Researchers in their study found evidence for 182 species of bacteria in skin samples. Eight percent were unknown species that had never before been described.
"The skin is home to a virtual zoo of bacteria," stated Dr Blaser. This study was published on February 5, 2007, in the online edition of the Proceedings of the National Academy of Sciences.
The researchers analyzed the bacteria on the forearms of six healthy subjects, three men and three women. According to Dr Blaser, this is essentially the first molecular study of the skin. He explained that the skin has been a terra incognita, an unknown world that he and his colleagues have set out to understand much like explorers.
In the new study, the researchers took swabs from the inner right and left forearms of six individuals picking the region halfway between the wrist and the elbow for its convenience. It is not where they wash their hands or undress. The researchers wanted to be able to compare two similar parts of the body. Because they also wanted to study change over time, they took swabs from four of the individuals eight to10 months after the first test.
The team used a powerful molecular method that involved extracting a subunit of genetic material called 16S ribosomal DNA from the samples to characterize the bacteria.
Roughly half, or 54.4 perecnt, of the bacteria identified in the samples represented the genera Propionibacteria, Corynebacteria, Staphylococcus and Streptococcus, which have long been considered more or less permanent residents in human skin.
The six individuals differed markedly in the overall composition of the bacterial populations on their skin. They only had four species of bacteria in common: Propionibacterium acnes, Corynebacterium tuberculostearicum, Streptococcus mitis and Finegoldia AB109769. “This is a surprise,” exclaimed Dr Gao. “But many things affecting the skin affect bacteria, such as the weather, exposure to light, and cosmetics use.”
Almost three-quarters, or 71.4 percent, of the total number of bacterial species were unique to individual subjects, suggesting that the skin surface is highly diversified in terms of the bacteria it harbors, according to the study. Three bacterial species were only found in the male subjects: Propionibacterium granulosum, Corynebacterium singulare, and Corynebacterium appendixes. While the sample is too small to draw conclusions, the scientists believe that women and men may harbor some different bacterial species on their skin.
In each individual, the bacterial populations varied over time while revealing a core set of bacteria for each individual. “The predominant bacteria don't change much,” said Dr Gao. “But the more transient bacteria did change over time.” “That suggests that there is a scaffold of bacteria present in everybody's skin. Some stay and others come and go, added Dr Gao.”
The next step for the research team is to look at diseased skin. “We plan to ask the question: Are the microbes in diseased skin, in certain diseases like psoriasis or eczema, different than the microbes in normal skin?” stated Dr Blaser.
According to Dr Blaser and his team, the skin, the largest organ in the human body, is a kind of zoo and some of the inhabitants are quite novel. Researchers in their study found evidence for 182 species of bacteria in skin samples. Eight percent were unknown species that had never before been described.
"The skin is home to a virtual zoo of bacteria," stated Dr Blaser. This study was published on February 5, 2007, in the online edition of the Proceedings of the National Academy of Sciences.
The researchers analyzed the bacteria on the forearms of six healthy subjects, three men and three women. According to Dr Blaser, this is essentially the first molecular study of the skin. He explained that the skin has been a terra incognita, an unknown world that he and his colleagues have set out to understand much like explorers.
In the new study, the researchers took swabs from the inner right and left forearms of six individuals picking the region halfway between the wrist and the elbow for its convenience. It is not where they wash their hands or undress. The researchers wanted to be able to compare two similar parts of the body. Because they also wanted to study change over time, they took swabs from four of the individuals eight to10 months after the first test.
The team used a powerful molecular method that involved extracting a subunit of genetic material called 16S ribosomal DNA from the samples to characterize the bacteria.
Roughly half, or 54.4 perecnt, of the bacteria identified in the samples represented the genera Propionibacteria, Corynebacteria, Staphylococcus and Streptococcus, which have long been considered more or less permanent residents in human skin.
The six individuals differed markedly in the overall composition of the bacterial populations on their skin. They only had four species of bacteria in common: Propionibacterium acnes, Corynebacterium tuberculostearicum, Streptococcus mitis and Finegoldia AB109769. “This is a surprise,” exclaimed Dr Gao. “But many things affecting the skin affect bacteria, such as the weather, exposure to light, and cosmetics use.”
Almost three-quarters, or 71.4 percent, of the total number of bacterial species were unique to individual subjects, suggesting that the skin surface is highly diversified in terms of the bacteria it harbors, according to the study. Three bacterial species were only found in the male subjects: Propionibacterium granulosum, Corynebacterium singulare, and Corynebacterium appendixes. While the sample is too small to draw conclusions, the scientists believe that women and men may harbor some different bacterial species on their skin.
In each individual, the bacterial populations varied over time while revealing a core set of bacteria for each individual. “The predominant bacteria don't change much,” said Dr Gao. “But the more transient bacteria did change over time.” “That suggests that there is a scaffold of bacteria present in everybody's skin. Some stay and others come and go, added Dr Gao.”
The next step for the research team is to look at diseased skin. “We plan to ask the question: Are the microbes in diseased skin, in certain diseases like psoriasis or eczema, different than the microbes in normal skin?” stated Dr Blaser.
Are Your Dishes Clean? What Kills E Coli and Salmonella Bacteria?
Food scientists at The Ohio State University wanted to see if cooler water could kill bacteria on dirty dishes like E. coli and salmonella. The study found that even when dishes were washed in cooler temperatures, it still cleaned enough bacteria away to levels accepted in the US FDA’s food code.
You've seen the restaurant reports -- health departments shut down hundreds of restaurants each week because they don't meet health standards. E. coli and salmonella outbreaks make customers sick -- dirty dishes could be to blame.
Restaurants clean plate after plate after plate -- but just how clean are the plates you're eating off? "You just can't go on looks -- you really have to have good techniques," said Melvin Pascall, food scientist at The Ohio State University.
The FDA recommends restaurants follow a three-step process when washing dishes -- scrub in soapy hot water at an uncomfortable 43°C (110°F), rinse with clean water, and then soak in sanitizer.
Food scientists at The Ohio State University wanted to see if cooler water could still kill bacteria. "Micro-organisms are smaller than our naked eyes can detect," Pascall said.
Milk and cheese provide a place for bacteria to grow, lipstick keeps bacteria from sticking. "The thing is -- you want to clean the utensil and make sure it's free from bacteria -- period," said Pascall.
Dishes are not created equally -- compared to ceramic plates, steel knives, spoons, forks and plastic trays are prime growing spots for bacteria.
The study also found that even when dishes were washed in cooler temperatures, it still cleaned enough bacteria away to levels accepted in the food and drug administration's food code. Although the study was aimed at restaurants, food scientists say to stay safe at home, wash your dishes right after using them, before the food dries and bacteria grows.
BACKGROUND: New research at Ohio State University reveals some interesting insights into how clean dishes become using manual washing. Scientists found that even when they washed dishes in cooler-than-recommended water, the bacteria levels on the dishware dropped to levels acceptable under current FDA regulations. This means that restaurant employees can use a more comfortable dishwashing technique and still end up with clean dishes.
LATHER, RINSE, REPEAT: When restaurants manually wash dishes, they follow a three-step process. Dishes are washed and scrubbed in soapy water, rinsed with clean water, and finally soaked in water containing germ-killing sanitizers. Employees often use water that is cooler than 43°C (110°F) -- the minimum washing temperature recommended by the FDA -- because it is uncomfortably hot. The FDA also requires that washing cause a 100,000-fold drop in the amounts of bacteria on those dishes.
ABOUT THE EXPERIMENT: To investigate the effectiveness of lower-temperature dishwashing tactics, the OSU researchers coated dishes individually with cheese, eggs, jelly, lipstick and milk, and then added Escherichia coli and Listeria innocua bacteria. Both these contaminants can survive for long periods of time if they make their way onto food dried onto dishes.
If those dishes are not thoroughly washed, they can sometimes cause food-borne disease outbreaks.
They let the food dry on the dishes for an hour, and then used different combinations of washing, rinsing and sanitizing before measuring the levels of microscopic organisms still clinging to the dishes, thereby determining the effectiveness of the cleaning.
WHAT THEY FOUND: The OSU researchers found that washing dishes in hot dishwater, followed by soaking in extra sanitizers, eliminated almost all of the bacteria on them, even when coated with dried on cheese. But dishes washed in soapy room-temperature water, rinsed, and then weakly sanitized with ammonium-based chemicals also achieved FDA-acceptable results.
However, all dishes are not created equal. Compared to ceramic plates, steel knives, spoons and plastic trays, steel forks proved more stubborn about hanging onto bacterial contamination, largely because of the prongs.
They recommended taking extra time to wash forks, especially those covered in sticky substances like cheese.
Also, milk dried onto glasses protected bacteria more than any other food, although it is still unclear why that should be the case.
Based on their findings, the OSU scientists recommend washing dishes right away before food dries, since otherwise bacteria will grow on them. It saves washing time and gets rid of problematic places where bacteria might be able to survive washing and drying.
Reported: August 1, 2007
Source: http://www.sciencedaily.com/videos/2007/0810-are_your_dishes_clean.htm
You've seen the restaurant reports -- health departments shut down hundreds of restaurants each week because they don't meet health standards. E. coli and salmonella outbreaks make customers sick -- dirty dishes could be to blame.
Restaurants clean plate after plate after plate -- but just how clean are the plates you're eating off? "You just can't go on looks -- you really have to have good techniques," said Melvin Pascall, food scientist at The Ohio State University.
The FDA recommends restaurants follow a three-step process when washing dishes -- scrub in soapy hot water at an uncomfortable 43°C (110°F), rinse with clean water, and then soak in sanitizer.
Food scientists at The Ohio State University wanted to see if cooler water could still kill bacteria. "Micro-organisms are smaller than our naked eyes can detect," Pascall said.
Milk and cheese provide a place for bacteria to grow, lipstick keeps bacteria from sticking. "The thing is -- you want to clean the utensil and make sure it's free from bacteria -- period," said Pascall.
Dishes are not created equally -- compared to ceramic plates, steel knives, spoons, forks and plastic trays are prime growing spots for bacteria.
The study also found that even when dishes were washed in cooler temperatures, it still cleaned enough bacteria away to levels accepted in the food and drug administration's food code. Although the study was aimed at restaurants, food scientists say to stay safe at home, wash your dishes right after using them, before the food dries and bacteria grows.
BACKGROUND: New research at Ohio State University reveals some interesting insights into how clean dishes become using manual washing. Scientists found that even when they washed dishes in cooler-than-recommended water, the bacteria levels on the dishware dropped to levels acceptable under current FDA regulations. This means that restaurant employees can use a more comfortable dishwashing technique and still end up with clean dishes.
LATHER, RINSE, REPEAT: When restaurants manually wash dishes, they follow a three-step process. Dishes are washed and scrubbed in soapy water, rinsed with clean water, and finally soaked in water containing germ-killing sanitizers. Employees often use water that is cooler than 43°C (110°F) -- the minimum washing temperature recommended by the FDA -- because it is uncomfortably hot. The FDA also requires that washing cause a 100,000-fold drop in the amounts of bacteria on those dishes.
ABOUT THE EXPERIMENT: To investigate the effectiveness of lower-temperature dishwashing tactics, the OSU researchers coated dishes individually with cheese, eggs, jelly, lipstick and milk, and then added Escherichia coli and Listeria innocua bacteria. Both these contaminants can survive for long periods of time if they make their way onto food dried onto dishes.
If those dishes are not thoroughly washed, they can sometimes cause food-borne disease outbreaks.
They let the food dry on the dishes for an hour, and then used different combinations of washing, rinsing and sanitizing before measuring the levels of microscopic organisms still clinging to the dishes, thereby determining the effectiveness of the cleaning.
WHAT THEY FOUND: The OSU researchers found that washing dishes in hot dishwater, followed by soaking in extra sanitizers, eliminated almost all of the bacteria on them, even when coated with dried on cheese. But dishes washed in soapy room-temperature water, rinsed, and then weakly sanitized with ammonium-based chemicals also achieved FDA-acceptable results.
However, all dishes are not created equal. Compared to ceramic plates, steel knives, spoons and plastic trays, steel forks proved more stubborn about hanging onto bacterial contamination, largely because of the prongs.
They recommended taking extra time to wash forks, especially those covered in sticky substances like cheese.
Also, milk dried onto glasses protected bacteria more than any other food, although it is still unclear why that should be the case.
Based on their findings, the OSU scientists recommend washing dishes right away before food dries, since otherwise bacteria will grow on them. It saves washing time and gets rid of problematic places where bacteria might be able to survive washing and drying.
Reported: August 1, 2007
Source: http://www.sciencedaily.com/videos/2007/0810-are_your_dishes_clean.htm
Definitions of words used in Food Microbiology
A glossary of words associated with Food Microbiology.
Acid dyes: Dyes that are anionic or have negatively charged groups such as carboxyls. Acid fast: Bacteria like the mycobacteria that cannot be easily decolorized with acid alcohol after being stained with dyes such as basic fuchsin.
Anaerobe: A microorganism that is capable of growing in the complete absence of oxygen. Some of these organisms may also be able to grow in oxygenated conditions (facultative aerobes), whereas others cannot tolerate oxygen and are killed when exposed to air. Such organisms are termed obligate anaerobes.
Antibody: An inducible immunoglobulin protein produced by B lymphocytes of the immune system, in humans and other higher animals, which recognizes and binds to a specific antigen molecule of a foreign substance introduced into the organism. When antibodies bind to corresponding antigens they set in motion a process to eliminate the antigens.
Antigen: Any foreign substance, such as virus, bacterium, or protein, which after introduction into an organism (humans and higher animals), elicits an immune response by stimulating the production of specific antibodies; or any large molecule which binds specifically to an antibody.
Antimicrobial: A chemical agent that kills microorganisms or inhibits their growth. Apoptosis: Programmed cell death, the body's normal method of ending the lifecycle of cells through the cellular self-destruction. When either heritable or somatic cell mutations cause malfunctions to occur in the apoptotic pathway, uncontrolled cell growth may proceed unchecked and cancer may result.
Bacterial growth: Can exhibit at least four different phases: lag phase, growth phase, stationary phase and death phase.
Bacterial strain: Population of bacterial cells all descended from a single pure isolate.
Base pair (bp): Two complementary nitrogenous bases in a DNA molecule, such as the nucleotide coupling of adenine with thymine (A:T) and guanine with cytosine (G:C); also, a unit of measurement for DNA sequences.
Biofilm: Adherent layer of bacteria and/or other microorganisms on a solid surface bound together in a bacterially-derived polysaccharide matrix that is protective for the organisms; generally occuring at a liquid/solid interface and often developing into a complex ecological community (e.g., dental plaque bound tother by dextrans).
Chromosome: A single DNA molecule that is the self-replicating genetic structure within the cell which carries the linear nucleotide sequence of genes. In humans (or eukaryotes), the DNA is supercoiled, compacted, and complexed with accessory proteins, and organized into a number of such structures. Normal human cells contain 46 chromosomes (except the germ cells, egg and sperm): 22 homologous pairs of autosomes and the sex-determining X and Y chromosomes (XX for females and XY for males). Prokaryotes carry their entire genome on one circular chromosome of DNA.
Commensal: Organisms existing in or on an animal or human without causing disease. Conjugation (or bio-conjugation): The chemical joining of a biomolecule to another.
Death phase: The death phase occurs when cells are being inactivated or killed because conditions no longer support growth or survival. Some environmental factors such as temperature can cause acute inactivation. Others may cause mild inactivation as with growth in the presence of organic acids.
DNA (deoxyribonucleic acid): The nucleic acid molecule consisting of deoxyribonucleotide building blocks that encode genetic information. The genome of most organisms is contained in a double-stranded, double-helical form held together with chemical bonds between each strand of complementary nucleotide base pairs.
DNA probe: A single-stranded piece of DNA that binds specifically to a complementary DNA sequence; the probe is labeled (e.g., with a fluorescent or radioactive tag) in order to detect its incorporation through hybridization with DNA in a sample.
Dot blot: A method for detecting proteins by the specific binding of an antibody or binding molecule to a sample spot on nitrocellulose paper. The bound sample is visualized using an enzymatic or fluorimetric reporter conjugated to the probe.
Doubling time: The time taken for a population to increase in number by a factor of two.
Enteric (entero-): Relating to the intestine. Enterotoxin: Proteins produced by bacteria that are either ingested as pre-formed toxins or are produced by a pathogen that has colonised the gastro-intestinal tract. Usually the toxin has specific targets and either disrupts cell function or kills the cell.
Eukaryote: (meaning "true nucleus") An organism which possesses a nucleus with a double layer of membrane and other membrane-bound organelles; includes such unicellular or multicellular members as all members of the protist, fungi, plant, and animal kingdoms.
Exons: The segment of a gene present in mature mRNA transcripts that specify the amino acid sequence of a polypeptide during translation; exons of a gene are linked together by mRNA splicing.
Exotoxin: Potent toxic substance formed and released extracellularly by species of certain bacteria. Exponential phase: The period in which the cells of a defined bacterial population are growing and dividing continuously.
Extracellular: Produced, then excreted outside the organism.
Facultative: Ability to adapt and live under various conditions.
Facultative anaerobe: Anaerobe that can survive with or without oxygen.
Flow cytometer: Analytical instrument for flow cytometry.
Flow cytometry: Automated analysis of cells or subcellular components by detection of the fluorescence or light-scatter of sample fractions passing in narrow-stream droplets through a laser beam.
Fluorophores: Molecules that produce a fluorescent emission when irradiated with light at a suitable excitation wavelength.
Fomite: Inanimate object capable of transmitting infectious organisms to a host, e.g., soiled clothes, tissues and handkerchiefs, food processing equipment, dishrags, etc. Gene amplification: The presence of multiple copies of a gene or segment of DNA; a mechanism by which proto-oncogenes are activated in malignant cells. A tumor cell amplifies, or copies, DNA segments as a result of cell signals or the effects of environmental insults.
Gene expression: The process by which the encoded information of the genome is converted into cellular components. The DNA-coding sequences of expressed genes include those that are transcribed into mRNA and then translated into proteins, and RNA that is transcribed from DNA, yet not translated into protein (i.e., transfer and ribosomal RNAs).
Gene mapping: A linear map determining the relative position of genes along a chromosome or plasmid. Distances are established by linkage analysis and measured in linkage units.
Gene: A nucleotide sequence of DNA that codes for a protein, or functional or structural RNA molecule; a locus on a chromosome. The element that determines a trait in an organism.
Genetic mutation: An alteration in the nucleotide sequence of a DNA molecule; often from one allelic form of a gene to another allele alternative.
Genome: The total amount of genetic material in a cell; in eukaryotes the haploid set of chromosomes of an organism. The chromosome set is species-specific for the number genes and linkage groups carried in genomic DNA.
Genomics: The study of genes and their biochemical function in an organism.
Genotype: The genetic constitution of an organism; or, a reference to an individual's particular allele pair at a specific gene locus in the genome.
Genotyping: Analysis of genotype.
Genus: Taxonomic level below Family and above Species. Gram-negative or Gram-positive: The classification given to bacteria according to their staining properties as defined by the Gram stain procedure.
Growth curve: A graph displaying the behaviour of a bacterial population over time. Growth phase: During the growth phase, cells grow exponentially and at a constant rate. The maximum slope of the curve is the specific growth rate of the organism. Cell growth is dependent upon the current environment (nutrients, temperature, pH, etc.), but is not dependent upon the previous physiological state. In the field of predictive microbiology, growth rate is commonly expressed as the change in cell number per time interval.
Growth rate: This is an expression of population increase in numbers expressed as log10 cfu/hour.
Haploid: A cell or individual with a genetic complement containing one copy of each nuclear chromosome. (Diploid refers to the condition when a eukaryotic cell possesses two sets of chromosomes.)
Humectant: A solute that binds free water in a food, reducing the amount of water available to the microorganisms.
Hybridize (or hybridization): The process where the hydrogen bonding of complementary DNA and/or RNA sequences forms a duplex molecule.
Immunoassays: A technique that detects and measures a specific antigen or biological substance by employing antibodies (e.g., dot blot, western blot, and ELISA).
in situ hybridization (ISH): Use of a nucleic acid probe to detect and identify specific complementary sequences of DNA in chromosomes or RNA in bacteria, eukaryotic cells, and tissue.
in vitro: ("in glass") Refers to the recreation of biological processes in an artificial environment such as a test tube.
in vivo: ("in living") Refers to biological processes within a living organism or cell.
Inoculum: A medium containing microorganisms to be introduced into fresh media or food source in an experiment. Intron: A nucleotide sequence intervening between exons (coding regions) that is excised from a gene transcript during RNA processing.
Kinetics: The properties of chemical agents or enzymes in the efficiency and speed of their action upon a chemical reaction.
Klebsiella: Gram-negative rods occur in human feces and clinical specimens, soil, water, grain, fruits, and vegetables. Some species are opportunistic pathogens. Kluyvera: Gram-negative rods occur in food, soil, sewage, and human clinical specimens. They are infrequently opportunistic pathogens. Kurthia: Gram-positive rods are widely distributed in the environment, and are common in animal feces and meat products. Lag phase: During the lag phase, cells increase in size but not in number because they are adapting to a new environment, and, synthesis and repair are taking place. The length of the lag phase depends on the current environment as well as the previous physiological state of the cells. Cells that are from a very different environment or are damaged from their previous physiological state may require more time to adjust. In some foods a lag phase does not exist which results in cells that are ready for immediate growth.
Lag time: The initial period in a bacterial population life when cells are adjusting to a new environment before commencing growth.
Legionella: Fastidious gram-negative rod is isolated from surface water, mud, and thermally polluted lakes and streams. There is no known soil or animal source. It is pathogenic for humans, causing pneumonia (Legionnaires’ disease) or a mild, febrile disease (Pontiac fever). Ligand: The molecule which binds to a protein molecule (e.g., receptor). As a ligand binds through the interaction of many weak, noncovalent bonds formed to the binding site of a protein, the tight binding of a ligand depends upon a precise fit to the surface-exposed amino acid residues on the protein.
Listeria: Gram-positive rod widely distributed in the environment. Some species are pathogenic for humans and animals (e.g. L. monocytogenes). Locus: (plural, loci) The specific site of a gene on a genetic map or chromosome.
Marker (genetic marker): Any genetically derived phenotypic difference used in the analysis of inheritance patterns or to differentiate between types of cells. An observable site on a chromosome that is heritable and can be either a genetically-expressed region or noncoding segment of DNA (intron).
Maximum population density: Point at which the maximum number of bacterial cells can exist in an environment.
Meiosis: Process that allows one diploid celll to divide in a special way to generate haploid cells in eukaryotes.
Mesophile: Microorganism able to grow well between 20°C and 45°C, having an optima of 30°C to 40°C. Many can sustain growth at below 10°C albeit very slow growth.
Metaphase: Stage in mitosis or meiosis during which the chromosomes are aligned along the equatorial plane of the cell.
Methylobacterium: Mostly isolated from water and leaf surface microflora, and are facultative methylotrophs, that is capable of growing on one-carbon compounds such as formate, formaldehyde, and methanol as the sole source of carbon and energy, as well as on a wide range of multicarbon substrates. Microaerophilllic environment: Environment with reduced oxygen concentrations, often below 5%. Carbon dioxide levels may approach 10%.
Microbacterium: Gram-positive rod is found in dairy products, sewage, and insects.
Microbial load: Total number of living microorganisms in a given volume or mass of microbiological media or food.
Micrococcus: Gram-positive cocci occur primarily on mammalian skin and in soil, but are commonly isolated from food products and the air.
Microorganism: A living organism too small to be seen with the naked eye. Mitosis: Process by which a cell separates its duplicated genome into two identical halves. It is generally followed immediately by cytokinesis which divides the cytoplasm and cell membrane. This results in two identical daughter cells with a roughly equal distribution of organelles and other cellular components.
Moraxella: Gram-negative rod is parasitic on the mucous membranes of humans and other warm-blooded animals. MRNA (messenger RNA): The RNA molecule, transcribed from the DNA of a gene, which serves as a template and encodes the amino acid sequence of a protein.
Multiplexing: Method by which many parameters are tested and processed simultaneously.
Native microflora: Microorganisms that are normally found within a food source (often referred to as spoilage organisms).
Northern blot: Technique used to separate and transfer mRNA from a gel to a filter in order to identify and locate mRNA sequences that are complementary to and hybridize with a labeled DNA probe.
Novosphingobium: Gram-negative rods were originally included with Sphingomonas (see Sphingomonas). Nucleic acid: Molecule composed of nucleotide subunits. See DNA and RNA.
Nucleotide: Basic building block of nucleic acids that is a monomeric molecule of DNA or RNA composed of: a pentose sugar (with 5-carbons such as deoxyribose in DNA, ribose in RNA), an organic nitrogenous base, and a phosophate group. DNA consists of the four bases: adenine (A), guanine (G), cytosine (C), and thymine (T); likewise for RNA, except for the substitution of uracil (U) for T.
Oligonucleotide: ("oligo" means few) A short length of DNA nucleotides, often used as primers for DNA synthesis or probes for arrays and ISH/FISH; usually referred to as "oligo(s)."
Opportunistic: Microorganism that will only cause disease in a patient with a poor or somehow weakened immune system.
Organelle: Microscopic bodies in the cytoplasm of cells that have distinctive functions (e.g., nucleus, mitochondria, endoplasmic reticulum, etc.).
Pasteurisation: Mild heat treatment process given to foods. The process is designed to eradicate potential vegetative pathogens (not bacterial spores) and reduce other microorganism numbers in an effort to decrease the rate of spoilage.
Pantoea: Gram-negative rods are isolated from plant surfaces, seeds, soil, and water, as well as from animals and human clinical specimens. They are opportunistic human pathogens.
Pathogen: Microorganism associated with disease in man.
pH: Measure of the acidity or alkalinity of a solution, defined as the - log10 of the hydrogen ion concentration.
Phenotype: Observable manifestation of a genetic trait, resulting from a specific genotype and its interaction with the environment.
Physical map: Map indicating physical locations on a DNA molecule such as restriction enzyme recognition sites, RFLPs, and genes; measured in base pairs (bp).
Predictive microbiology: Area of food microbiology that uses mathematical models to define growth kinetics of microorganisms in food.
Primary model: Model that describes changes in microbial numbers in response to time.
Primer: Short segment of DNA or RNA that anneals to a single strand of DNA in order to initiate template-directed synthesis and extend a new DNA strand by the enzymatic action of DNA polymerase to produce a duplex-stranded molecule.
Probe: Single-stranded DNA or RNA molecule of specific base sequence, either radioactively or fluorescently labeled, that is used to identify the complementary nucleotide sequence by hybridization to the DNA fragment or gene of interest.
Protein translocation: Spatial movement of protein within a cell (e.g., from the cytoplasm to nucleus, or into organelles).
Protein: High-molecular weight biological molecule composed of a polymer of amino acids linked via peptide bonds; may consist of more than one polypeptide molecule that is folded into complex shapes such as helices or sheet-like structures. Proteins are encoded by the specific sequence of DNA nucleotides in a gene and give rise to the structure, function, and regulation of cells, tissues, and organs within the body. Protein classes include enzymes, antibodies, receptors, hormones, and growth factors.
Proteome: Entire protein make-up of a particular organism.
Proteomics: Study of proteins and their biochemical function in an organism.
Providencia: Gram-negative rods are isolated from human clinical specimens and from penguins.
Pseudomonas: Gram-negative rod is widely distributed in nature. Some species are pathogenic for humans, animals, or plants (e.g. P. aeruginosa).
Psychrobacter: Gram-negative rod is associated with fish, processed meat and poultry products. Some strains have been isolated from pathological specimens from humans and animals.
Psychrotroph: Microorganism able to grow well between 0°C and 7°C, having an optima of 20°C to 30°C.
Rahnella: Gram-negative rods occur in freshwater. They are occasionally isolated from human clinical specimens, but are not considered clinically significant.
Ralstonia: see Pseudomonas.
Raoultella: see Klebsiella.
Rathayibacter: Some of these species are phytopathogens of terrestial plants. Their main habitats are their respective plant hosts.
Receptor: Surface-exposed membrane protein on a cell which binds to a specific ligand molecule with high affinity, in order to transmit an extracellular signal and trigger intracellular biochemical events within the target cell.
Reporter: Gene which codes for an easily measured protein product and is fused downstream of the gene of interest in order to assess the activity in the region upstream of the reporter gene. Colorimetric and fluorimetric reporters also can be conjugated to probes to monitor biological events.
Rhodococcus: Aerobic, Gram-positive actinomycetes. These widely-occurring organisms are of considerable environmental and biotechnological importance due to their broad metabolic diversity and array of unique enzymatic capabilities, plus their capacity to degrade hydro-carbons. They are able to survive for a long time in soil. They are the most efficient in oil degradation and, relatively speaking, the most abundant in soils and marine environments. Rhizobium: Group of small, rod-shaped, gram-negative bacteria, which are able to produce nodules on the roots, or on some cases the stems, of leguminous plants.
RNA (ribonucleic acid): DNA-like organic molecule that consists of nucleotide subunits--such as adenine, guanine, cytosine, and uracil--which contain ribose sugars linked through phosphodiester bonds. Different types of RNA function in the process of gene expression.
Somatic cell mutation: Mutation in a cell that is acquired during the lifetime of an organism and which cannot be genetically inherited by offspring.
Somatic cell: Any cell in the body except the germ-line cells (sperm or egg cells).
Southern blot: Procedure which transfers elecrophoretically separated DNA fragments on an agarose gel to nitrocellulose filters for detection by hybridization with a labeled probe complementary to the sequence of interest; the position on the filter of the probe, when exposed to x-ray film, appears as a band on an autoradiogram.
Sphingobacterium: Gram-negative rod found in soil, on plants, foodstuffs, and in water sources. Sphingobium: Gram negative rods were originally included with Sphingomonas (see Sphingomonas). Sphingomonas: Relatively new genus derived from Pseudomonas paucimobilis. These organisms are widely distributed, including having been found in water. Only Sphingomonas paucimobilis is considered clinically significant, and has been isolated from a variety of clinical specimens
Spoilage organisms: Microorganisms naturally found within a food source that cause food spoilage.
Staphylococcus: This gram-positive coccus is mainly associated with the skin and mucous membranes of warm-blooded vertebrates, but they are often isolated from food products, dust and water. Some species are opportunistic pathogens of humans and animals, or produce extracellular toxins. Stationary phase: The stationary phase occurs at the maximum population density, the point at which the maximum number of bacterial cells can exist in an environment. This typically represents the carrying capacity of the environment. However, environmental factors such as pH, preservatives, antimicrobials, native microflora and atmospheric composition as well as depletion of growth-limiting nutrients can affect the maximum population density.
Stenotrophomonas: see Pseudomonas. Sub-lethal injury: This is cellular damage which results in disruption of metabolic processes which, under ideal conditions, is repairable. Such damage must be repaired before normal growth can recommence.
Tertiary model: Computer software routines that turn the primary and secondary models into "user-friendly" programs.
Tsukamurella: Gram-positive rods are isolated from soil, human sputum, and parts of bed bugs. Some strains can be pathogenic.
Toxins: Compounds produced by a microorganism that are poisonous to other organisms. Vegetative cell: The vegetative cell state is the form in which an organism is able to grow and divide continuously, given favourable conditions. Unlike endospores, vegetative cells are relatively poor at surviving environmental stresses such as high temperature and drying.
Water activity (aW): Water activity is a measure of the amount of free unassociated water molecules in a system. It runs on a scale of 0 to 1.0, where pure water equals 1.0. This parameter can also be expressed as a percentage referred to as the relative humidity. It is influenced by dissolved solutes and insoluble food components which act to bind water, thus reducing the available free water and hence aW value.
Weeksella: Gram-negative rod is not known in the general environment. It is apparently a parasite, saprophyte, or commensal of the internal surfaces of humans or other warm-blooded animals. Western blot: A technique which transfers proteins electrophoretically separated in a polyacrylamide gel to a nitrocellulose membrane and uses specific antibodies to bind, locate, and visualize the protein of interest.
Yersinia: Gram-negative rods occur in a broad spectrum of habitats, including humans, animals, soil, water, dairy products, and other foods. Some species are pathogenic for humans and animals; others are opportunistic pathogens, yet others are nonpathogenic.
Xanthomonas: Most Gram-negative rods are plant pathogens, or occur in association with plants. X.maltophilia is the only exception, being an opportunistic pathogen of humans.
Zoonotic: Microorganism normally found in or on animals.
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Acid dyes: Dyes that are anionic or have negatively charged groups such as carboxyls. Acid fast: Bacteria like the mycobacteria that cannot be easily decolorized with acid alcohol after being stained with dyes such as basic fuchsin.
Acid-fast staining: Staining procedure that differentiates between bacteria based on their ability to retain a dye when washed with an acid alcohol solution.
Acidophile: Microorganism that has its growth optimum between about pH 0 and 5.5.
Actinobacteria: Group of gram-positive bacteria containing the actinomycetes and their high G 1 C relatives.
Actinomycete: Aerobic, gram-positive bacterium that forms branching filaments (hyphae) and asexual spores.
Aerobe: The descriptive name given to a microorganism that can grow in conditions where oxygen is present. Such organisms are capable of growing in normal air, equivalent to 20% oxygen, or in aerated liquids containing dissolved oxygen. Many aerobes are equally able to grow in the absence of oxygen. These are termed facultative anaerobes.
Allele: One of two or more alternative nucleotide sequences at a single gene locus which occurs on either of two homologous chromosomes in a diploid organism. Anaerobe: A microorganism that is capable of growing in the complete absence of oxygen. Some of these organisms may also be able to grow in oxygenated conditions (facultative aerobes), whereas others cannot tolerate oxygen and are killed when exposed to air. Such organisms are termed obligate anaerobes.
Antibody: An inducible immunoglobulin protein produced by B lymphocytes of the immune system, in humans and other higher animals, which recognizes and binds to a specific antigen molecule of a foreign substance introduced into the organism. When antibodies bind to corresponding antigens they set in motion a process to eliminate the antigens.
Antigen: Any foreign substance, such as virus, bacterium, or protein, which after introduction into an organism (humans and higher animals), elicits an immune response by stimulating the production of specific antibodies; or any large molecule which binds specifically to an antibody.
Antimicrobial: A chemical agent that kills microorganisms or inhibits their growth. Apoptosis: Programmed cell death, the body's normal method of ending the lifecycle of cells through the cellular self-destruction. When either heritable or somatic cell mutations cause malfunctions to occur in the apoptotic pathway, uncontrolled cell growth may proceed unchecked and cancer may result.
Bacterial growth: Can exhibit at least four different phases: lag phase, growth phase, stationary phase and death phase.
Bacterial strain: Population of bacterial cells all descended from a single pure isolate.
Base pair (bp): Two complementary nitrogenous bases in a DNA molecule, such as the nucleotide coupling of adenine with thymine (A:T) and guanine with cytosine (G:C); also, a unit of measurement for DNA sequences.
Biofilm: Adherent layer of bacteria and/or other microorganisms on a solid surface bound together in a bacterially-derived polysaccharide matrix that is protective for the organisms; generally occuring at a liquid/solid interface and often developing into a complex ecological community (e.g., dental plaque bound tother by dextrans).
Bleaching: The loss of fluorescence usually due to photochemical reactions.
cDNA (complementary or copy DNA): DNA copies synthesized from a messenger RNA template using the enzyme reverse transcriptase; the single-stranded copy is often used as a probe to identify complementary sequences in DNA fragments or genes of interest. Chromosome: A single DNA molecule that is the self-replicating genetic structure within the cell which carries the linear nucleotide sequence of genes. In humans (or eukaryotes), the DNA is supercoiled, compacted, and complexed with accessory proteins, and organized into a number of such structures. Normal human cells contain 46 chromosomes (except the germ cells, egg and sperm): 22 homologous pairs of autosomes and the sex-determining X and Y chromosomes (XX for females and XY for males). Prokaryotes carry their entire genome on one circular chromosome of DNA.
Coccus: (singular): Spherical-shaped cell; cocci (plural).
Coliform bacteria (coliforms): Any fermentative (specifically lactose-fermenting) Gram-negative anaerobic enteric bacilli (E. coli-like).
Death phase: The death phase occurs when cells are being inactivated or killed because conditions no longer support growth or survival. Some environmental factors such as temperature can cause acute inactivation. Others may cause mild inactivation as with growth in the presence of organic acids.
DNA (deoxyribonucleic acid): The nucleic acid molecule consisting of deoxyribonucleotide building blocks that encode genetic information. The genome of most organisms is contained in a double-stranded, double-helical form held together with chemical bonds between each strand of complementary nucleotide base pairs.
DNA probe: A single-stranded piece of DNA that binds specifically to a complementary DNA sequence; the probe is labeled (e.g., with a fluorescent or radioactive tag) in order to detect its incorporation through hybridization with DNA in a sample.
Dot blot: A method for detecting proteins by the specific binding of an antibody or binding molecule to a sample spot on nitrocellulose paper. The bound sample is visualized using an enzymatic or fluorimetric reporter conjugated to the probe.
Doubling time: The time taken for a population to increase in number by a factor of two.
Enteric (entero-): Relating to the intestine. Enterotoxin: Proteins produced by bacteria that are either ingested as pre-formed toxins or are produced by a pathogen that has colonised the gastro-intestinal tract. Usually the toxin has specific targets and either disrupts cell function or kills the cell.
Eukaryote: (meaning "true nucleus") An organism which possesses a nucleus with a double layer of membrane and other membrane-bound organelles; includes such unicellular or multicellular members as all members of the protist, fungi, plant, and animal kingdoms.
Exons: The segment of a gene present in mature mRNA transcripts that specify the amino acid sequence of a polypeptide during translation; exons of a gene are linked together by mRNA splicing.
Exotoxin: Potent toxic substance formed and released extracellularly by species of certain bacteria. Exponential phase: The period in which the cells of a defined bacterial population are growing and dividing continuously.
Extracellular: Produced, then excreted outside the organism.
Facultative: Ability to adapt and live under various conditions.
Facultative anaerobe: Anaerobe that can survive with or without oxygen.
Family: Taxonomic level below order and above genus.
Fastidious: Complex nutritional or cultural requirements, making isolation and culture of a fastidious organism more difficult.
Fermentation: Enzymatic breakdown (catabolism) of carbohydrates generally in the absence of oxygen.
Fimbriae: Short, hair-like projections or appendages (organelles) on the outer surface of certain bacteria composed of protein subunits (pilin) extending outward from the surface that act as a virulence factor by promoting adherence; formerly known as pili; fimbria (singular).
Flagellum: whip-like bacterial locomotory (provide motility) organelles anchored in the cell membranes that are composed of helically-coiled protein subunits (flagellin); flagella (plural).FISH (Fluorescence In Situ Hybridization): A technique that employs fluorescent molecular tags to detect probes hybridized to chromosomes or chromatin; useful for genetic mapping and detecting chromosomal abnormalities. Flow cytometer: Analytical instrument for flow cytometry.
Flow cytometry: Automated analysis of cells or subcellular components by detection of the fluorescence or light-scatter of sample fractions passing in narrow-stream droplets through a laser beam.
Fluorophores: Molecules that produce a fluorescent emission when irradiated with light at a suitable excitation wavelength.
Fomite: Inanimate object capable of transmitting infectious organisms to a host, e.g., soiled clothes, tissues and handkerchiefs, food processing equipment, dishrags, etc. Gene amplification: The presence of multiple copies of a gene or segment of DNA; a mechanism by which proto-oncogenes are activated in malignant cells. A tumor cell amplifies, or copies, DNA segments as a result of cell signals or the effects of environmental insults.
Gene expression: The process by which the encoded information of the genome is converted into cellular components. The DNA-coding sequences of expressed genes include those that are transcribed into mRNA and then translated into proteins, and RNA that is transcribed from DNA, yet not translated into protein (i.e., transfer and ribosomal RNAs).
Gene mapping: A linear map determining the relative position of genes along a chromosome or plasmid. Distances are established by linkage analysis and measured in linkage units.
Gene: A nucleotide sequence of DNA that codes for a protein, or functional or structural RNA molecule; a locus on a chromosome. The element that determines a trait in an organism.
Genetic mutation: An alteration in the nucleotide sequence of a DNA molecule; often from one allelic form of a gene to another allele alternative.
Genome: The total amount of genetic material in a cell; in eukaryotes the haploid set of chromosomes of an organism. The chromosome set is species-specific for the number genes and linkage groups carried in genomic DNA.
Genomics: The study of genes and their biochemical function in an organism.
Genotype: The genetic constitution of an organism; or, a reference to an individual's particular allele pair at a specific gene locus in the genome.
Genotyping: Analysis of genotype.
Genus: Taxonomic level below Family and above Species. Gram-negative or Gram-positive: The classification given to bacteria according to their staining properties as defined by the Gram stain procedure.
Growth curve: A graph displaying the behaviour of a bacterial population over time. Growth phase: During the growth phase, cells grow exponentially and at a constant rate. The maximum slope of the curve is the specific growth rate of the organism. Cell growth is dependent upon the current environment (nutrients, temperature, pH, etc.), but is not dependent upon the previous physiological state. In the field of predictive microbiology, growth rate is commonly expressed as the change in cell number per time interval.
Growth rate: This is an expression of population increase in numbers expressed as log10 cfu/hour.
Haploid: A cell or individual with a genetic complement containing one copy of each nuclear chromosome. (Diploid refers to the condition when a eukaryotic cell possesses two sets of chromosomes.)
Humectant: A solute that binds free water in a food, reducing the amount of water available to the microorganisms.
Hybridize (or hybridization): The process where the hydrogen bonding of complementary DNA and/or RNA sequences forms a duplex molecule.
Immunoassays: A technique that detects and measures a specific antigen or biological substance by employing antibodies (e.g., dot blot, western blot, and ELISA).
in situ hybridization (ISH): Use of a nucleic acid probe to detect and identify specific complementary sequences of DNA in chromosomes or RNA in bacteria, eukaryotic cells, and tissue.
in vitro: ("in glass") Refers to the recreation of biological processes in an artificial environment such as a test tube.
in vivo: ("in living") Refers to biological processes within a living organism or cell.
Inoculum: A medium containing microorganisms to be introduced into fresh media or food source in an experiment. Intron: A nucleotide sequence intervening between exons (coding regions) that is excised from a gene transcript during RNA processing.
Kinetics: The properties of chemical agents or enzymes in the efficiency and speed of their action upon a chemical reaction.
Klebsiella: Gram-negative rods occur in human feces and clinical specimens, soil, water, grain, fruits, and vegetables. Some species are opportunistic pathogens. Kluyvera: Gram-negative rods occur in food, soil, sewage, and human clinical specimens. They are infrequently opportunistic pathogens. Kurthia: Gram-positive rods are widely distributed in the environment, and are common in animal feces and meat products. Lag phase: During the lag phase, cells increase in size but not in number because they are adapting to a new environment, and, synthesis and repair are taking place. The length of the lag phase depends on the current environment as well as the previous physiological state of the cells. Cells that are from a very different environment or are damaged from their previous physiological state may require more time to adjust. In some foods a lag phase does not exist which results in cells that are ready for immediate growth.
Lag time: The initial period in a bacterial population life when cells are adjusting to a new environment before commencing growth.
Legionella: Fastidious gram-negative rod is isolated from surface water, mud, and thermally polluted lakes and streams. There is no known soil or animal source. It is pathogenic for humans, causing pneumonia (Legionnaires’ disease) or a mild, febrile disease (Pontiac fever). Ligand: The molecule which binds to a protein molecule (e.g., receptor). As a ligand binds through the interaction of many weak, noncovalent bonds formed to the binding site of a protein, the tight binding of a ligand depends upon a precise fit to the surface-exposed amino acid residues on the protein.
Listeria: Gram-positive rod widely distributed in the environment. Some species are pathogenic for humans and animals (e.g. L. monocytogenes). Locus: (plural, loci) The specific site of a gene on a genetic map or chromosome.
Marker (genetic marker): Any genetically derived phenotypic difference used in the analysis of inheritance patterns or to differentiate between types of cells. An observable site on a chromosome that is heritable and can be either a genetically-expressed region or noncoding segment of DNA (intron).
Maximum population density: Point at which the maximum number of bacterial cells can exist in an environment.
Meiosis: Process that allows one diploid celll to divide in a special way to generate haploid cells in eukaryotes.
Mesophile: Microorganism able to grow well between 20°C and 45°C, having an optima of 30°C to 40°C. Many can sustain growth at below 10°C albeit very slow growth.
Metaphase: Stage in mitosis or meiosis during which the chromosomes are aligned along the equatorial plane of the cell.
Methylobacterium: Mostly isolated from water and leaf surface microflora, and are facultative methylotrophs, that is capable of growing on one-carbon compounds such as formate, formaldehyde, and methanol as the sole source of carbon and energy, as well as on a wide range of multicarbon substrates. Microaerophilllic environment: Environment with reduced oxygen concentrations, often below 5%. Carbon dioxide levels may approach 10%.
Microbacterium: Gram-positive rod is found in dairy products, sewage, and insects.
Microbial load: Total number of living microorganisms in a given volume or mass of microbiological media or food.
Micrococcus: Gram-positive cocci occur primarily on mammalian skin and in soil, but are commonly isolated from food products and the air.
Microorganism: A living organism too small to be seen with the naked eye. Mitosis: Process by which a cell separates its duplicated genome into two identical halves. It is generally followed immediately by cytokinesis which divides the cytoplasm and cell membrane. This results in two identical daughter cells with a roughly equal distribution of organelles and other cellular components.
Moraxella: Gram-negative rod is parasitic on the mucous membranes of humans and other warm-blooded animals. MRNA (messenger RNA): The RNA molecule, transcribed from the DNA of a gene, which serves as a template and encodes the amino acid sequence of a protein.
Multiplexing: Method by which many parameters are tested and processed simultaneously.
Native microflora: Microorganisms that are normally found within a food source (often referred to as spoilage organisms).
Northern blot: Technique used to separate and transfer mRNA from a gel to a filter in order to identify and locate mRNA sequences that are complementary to and hybridize with a labeled DNA probe.
Novosphingobium: Gram-negative rods were originally included with Sphingomonas (see Sphingomonas). Nucleic acid: Molecule composed of nucleotide subunits. See DNA and RNA.
Nucleotide: Basic building block of nucleic acids that is a monomeric molecule of DNA or RNA composed of: a pentose sugar (with 5-carbons such as deoxyribose in DNA, ribose in RNA), an organic nitrogenous base, and a phosophate group. DNA consists of the four bases: adenine (A), guanine (G), cytosine (C), and thymine (T); likewise for RNA, except for the substitution of uracil (U) for T.
Oligonucleotide: ("oligo" means few) A short length of DNA nucleotides, often used as primers for DNA synthesis or probes for arrays and ISH/FISH; usually referred to as "oligo(s)."
Opportunistic: Microorganism that will only cause disease in a patient with a poor or somehow weakened immune system.
Organelle: Microscopic bodies in the cytoplasm of cells that have distinctive functions (e.g., nucleus, mitochondria, endoplasmic reticulum, etc.).
Pasteurisation: Mild heat treatment process given to foods. The process is designed to eradicate potential vegetative pathogens (not bacterial spores) and reduce other microorganism numbers in an effort to decrease the rate of spoilage.
Pantoea: Gram-negative rods are isolated from plant surfaces, seeds, soil, and water, as well as from animals and human clinical specimens. They are opportunistic human pathogens.
Pathogen: Microorganism associated with disease in man.
pH: Measure of the acidity or alkalinity of a solution, defined as the - log10 of the hydrogen ion concentration.
Phenotype: Observable manifestation of a genetic trait, resulting from a specific genotype and its interaction with the environment.
Physical map: Map indicating physical locations on a DNA molecule such as restriction enzyme recognition sites, RFLPs, and genes; measured in base pairs (bp).
Predictive microbiology: Area of food microbiology that uses mathematical models to define growth kinetics of microorganisms in food.
Primary model: Model that describes changes in microbial numbers in response to time.
Primer: Short segment of DNA or RNA that anneals to a single strand of DNA in order to initiate template-directed synthesis and extend a new DNA strand by the enzymatic action of DNA polymerase to produce a duplex-stranded molecule.
Probe: Single-stranded DNA or RNA molecule of specific base sequence, either radioactively or fluorescently labeled, that is used to identify the complementary nucleotide sequence by hybridization to the DNA fragment or gene of interest.
Protein translocation: Spatial movement of protein within a cell (e.g., from the cytoplasm to nucleus, or into organelles).
Protein: High-molecular weight biological molecule composed of a polymer of amino acids linked via peptide bonds; may consist of more than one polypeptide molecule that is folded into complex shapes such as helices or sheet-like structures. Proteins are encoded by the specific sequence of DNA nucleotides in a gene and give rise to the structure, function, and regulation of cells, tissues, and organs within the body. Protein classes include enzymes, antibodies, receptors, hormones, and growth factors.
Proteome: Entire protein make-up of a particular organism.
Proteomics: Study of proteins and their biochemical function in an organism.
Providencia: Gram-negative rods are isolated from human clinical specimens and from penguins.
Pseudomonas: Gram-negative rod is widely distributed in nature. Some species are pathogenic for humans, animals, or plants (e.g. P. aeruginosa).
Psychrobacter: Gram-negative rod is associated with fish, processed meat and poultry products. Some strains have been isolated from pathological specimens from humans and animals.
Psychrotroph: Microorganism able to grow well between 0°C and 7°C, having an optima of 20°C to 30°C.
Rahnella: Gram-negative rods occur in freshwater. They are occasionally isolated from human clinical specimens, but are not considered clinically significant.
Ralstonia: see Pseudomonas.
Raoultella: see Klebsiella.
Rathayibacter: Some of these species are phytopathogens of terrestial plants. Their main habitats are their respective plant hosts.
Receptor: Surface-exposed membrane protein on a cell which binds to a specific ligand molecule with high affinity, in order to transmit an extracellular signal and trigger intracellular biochemical events within the target cell.
Reporter: Gene which codes for an easily measured protein product and is fused downstream of the gene of interest in order to assess the activity in the region upstream of the reporter gene. Colorimetric and fluorimetric reporters also can be conjugated to probes to monitor biological events.
Rhodococcus: Aerobic, Gram-positive actinomycetes. These widely-occurring organisms are of considerable environmental and biotechnological importance due to their broad metabolic diversity and array of unique enzymatic capabilities, plus their capacity to degrade hydro-carbons. They are able to survive for a long time in soil. They are the most efficient in oil degradation and, relatively speaking, the most abundant in soils and marine environments. Rhizobium: Group of small, rod-shaped, gram-negative bacteria, which are able to produce nodules on the roots, or on some cases the stems, of leguminous plants.
RNA (ribonucleic acid): DNA-like organic molecule that consists of nucleotide subunits--such as adenine, guanine, cytosine, and uracil--which contain ribose sugars linked through phosphodiester bonds. Different types of RNA function in the process of gene expression.
Saprophyte: Microorganism that normally grows on dead material.
Secondary model: Model that predicts changes in primary model parameters based on environmental conditions.
Serratia: Gram-negative rods occur in human clinical specimens, soil, water, plant surfaces, and other environmental sites, digestive tracts of rodents, and insects. Some species are opportunistic pathogens.
SNP (Single Nucleotide Polymorphism): Variations in the sequence of DNA among individuals that are present in humans with a frequency of about once in every 1000 bases, and useful in assessing the patterns of inheritance in genetic linkage studies. Somatic cell mutation: Mutation in a cell that is acquired during the lifetime of an organism and which cannot be genetically inherited by offspring.
Somatic cell: Any cell in the body except the germ-line cells (sperm or egg cells).
Southern blot: Procedure which transfers elecrophoretically separated DNA fragments on an agarose gel to nitrocellulose filters for detection by hybridization with a labeled probe complementary to the sequence of interest; the position on the filter of the probe, when exposed to x-ray film, appears as a band on an autoradiogram.
Sphingobacterium: Gram-negative rod found in soil, on plants, foodstuffs, and in water sources. Sphingobium: Gram negative rods were originally included with Sphingomonas (see Sphingomonas). Sphingomonas: Relatively new genus derived from Pseudomonas paucimobilis. These organisms are widely distributed, including having been found in water. Only Sphingomonas paucimobilis is considered clinically significant, and has been isolated from a variety of clinical specimens
Spoilage organisms: Microorganisms naturally found within a food source that cause food spoilage.
Staphylococcus: This gram-positive coccus is mainly associated with the skin and mucous membranes of warm-blooded vertebrates, but they are often isolated from food products, dust and water. Some species are opportunistic pathogens of humans and animals, or produce extracellular toxins. Stationary phase: The stationary phase occurs at the maximum population density, the point at which the maximum number of bacterial cells can exist in an environment. This typically represents the carrying capacity of the environment. However, environmental factors such as pH, preservatives, antimicrobials, native microflora and atmospheric composition as well as depletion of growth-limiting nutrients can affect the maximum population density.
Stenotrophomonas: see Pseudomonas. Sub-lethal injury: This is cellular damage which results in disruption of metabolic processes which, under ideal conditions, is repairable. Such damage must be repaired before normal growth can recommence.
Tertiary model: Computer software routines that turn the primary and secondary models into "user-friendly" programs.
Tsukamurella: Gram-positive rods are isolated from soil, human sputum, and parts of bed bugs. Some strains can be pathogenic.
Toxins: Compounds produced by a microorganism that are poisonous to other organisms. Vegetative cell: The vegetative cell state is the form in which an organism is able to grow and divide continuously, given favourable conditions. Unlike endospores, vegetative cells are relatively poor at surviving environmental stresses such as high temperature and drying.
Water activity (aW): Water activity is a measure of the amount of free unassociated water molecules in a system. It runs on a scale of 0 to 1.0, where pure water equals 1.0. This parameter can also be expressed as a percentage referred to as the relative humidity. It is influenced by dissolved solutes and insoluble food components which act to bind water, thus reducing the available free water and hence aW value.
Weeksella: Gram-negative rod is not known in the general environment. It is apparently a parasite, saprophyte, or commensal of the internal surfaces of humans or other warm-blooded animals. Western blot: A technique which transfers proteins electrophoretically separated in a polyacrylamide gel to a nitrocellulose membrane and uses specific antibodies to bind, locate, and visualize the protein of interest.
Yersinia: Gram-negative rods occur in a broad spectrum of habitats, including humans, animals, soil, water, dairy products, and other foods. Some species are pathogenic for humans and animals; others are opportunistic pathogens, yet others are nonpathogenic.
Xanthomonas: Most Gram-negative rods are plant pathogens, or occur in association with plants. X.maltophilia is the only exception, being an opportunistic pathogen of humans.
Zoonotic: Microorganism normally found in or on animals.
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