Louis Pasteur is also known as the father of microbiology. He has many contributions to microbiology:
- He has proposed the principles of fermentation for the preservation of food.
- He introduced sterilization techniques and developed steam sterilizers, hot air oven, and autoclave.
- He described the method of pasteurization of milk.
- He had also contributed for designing the vaccines against several diseases such as anthrax, fowl cholera, and rabies
- He disproved the theory of spontaneous generation of disease and postulated the ‘germ theory of disease’. He stated that disease cannot be caused by bad air or vapor, but it is produced by the microorganisms present in the air.
- Liquid media concept- He used nutrient broth to grow microorganisms.
- He was the founder of the Pasteur Institute, Paris.
Louis Pasteur proposed:
• Principles of fermentation
• Pasteurization of milk
• Sterilization techniques
• The germ theory of disease
Robert Koch provided remarkable contributions to the field of microbiology:
- He used solid media for the culture of bacteria-Eilshemius Hesse, the wife of Walther Hesse, one of Koch’s assistants had suggested the use of agar as a solidifying agent.
- He also introduced methods for isolation of bacteria in pure culture.
- Described the hanging drop method for testing motility.
- Discovered bacteria such as the anthrax bacilli, tubercle bacilli, and cholera bacilli.
- Introduced staining techniques by using aniline dye.
- Koch’s phenomenon: Robert Koch observed that guinea pigs already infected with tubercle bacillus developed a hypersensitivity reaction when injected with tubercle bacilli or its protein. This reaction is called Koch’s phenomenon.
According to Koch’s postulates, a microorganism can be accepted as the causative agent of an infectious disease only if the following conditions are fulfilled:
i. The microorganism should be constantly associated with the lesions of the disease.
ii. It should be possible to isolate the organism in pure culture from the lesions of the disease.
iii. The same disease must result when the isolated microorganism is inoculated into a suitable laboratory animal.
iv. It should be possible to re-isolate the organism in pure culture from the lesions produced in the experimental animals.
An additional fifth criterion was introduced subsequently which states that antibody to the causative organism should be demonstrable in the patient’s serum.
Exceptions to Koch’s postulates: It is observed that it is not always possible to apply these postulates to study all the human diseases.
There are some bacteria that do not satisfy all the four criteria of Koch’s postulates. Those organisms are:
• Mycobacterium leprae and Treponema pallidum: They cannot be grown in vitro; however can be maintained in animals.
• Neisseria gonorrhoeae: There is no animal model; however, bacteria can be grown in vitro.
Molecular Koch’s postulates: It was a modification of Koch’s postulates (by Stanley Falkow). He stated that gene (coding for virulence) of a microorganism should satisfy all the criteria of Koch’s postulates rather than the microorganism itself.
- He was the first to report the acid-fast nature of tubercle bacillus.
- He developed techniques to stain tissues and blood cells.
- He proposed a toxin-antitoxin interaction called an Ehrlich phenomenon and also introduced methods of standardizing toxin and antitoxin
- He proposed the ‘side-chain theory for antibody production’.
- He discovered ‘salvarsan’, an arsenical compound (magic bullet) for treatment of syphilis, hence known as the father of chemotherapy.
- The bacteria ‘Ehrlichia’was named after him.
Other Important Contributors in Microbiology
1. Antonie Philips van Leeuwenhoek: Discovered single-lens microscope and named organisms as ‘Little animalcules’.
2. Edward Jenner: Developed the first vaccine of the world, the smallpox vaccine by using cowpox virus.
3. Joseph Lister: He is considered to be the father of antiseptic surgery. He used carbolic acid during surgery.
4. Hans Christian Gram: He developed ‘Gram stain’.
5. Ernst Ruska: He was the founder of the electron microscope.
6. Alexander Fleming: He discovered the antibiotic penicillin.
7. Elie Metchnikoff: He described phagocytosis and termed phagocytes.
8. Kleinberger: He described the existence of L forms of bacteria.
9. Barbara McClintock: She described transposons.
10. Walter Gilbert and Frederick Sanger: were the first to develop (1977) the method of DNA sequencing.
11. Karry B Mullis: Discovered polymerase chain reaction (PCR).
Apurba Sankar Sastry and Sandhya Bhat K. 2018. Review of Microbiology and Immunology. 6th Edition. Jaypee Brothers Medical Publishers (P) Ltd. (Click here to buy this book from AMAZON)