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.