Microbiology:-
> Microbiology is the study of living organisms of microscopic size.
> The term microbiology was given by French chemist Louis Pasteur.
> The term microbe was first used by Sedillot (1878).
> The two main branches of microbiology are:-
i. Bacteriology
ii. Virology
1. Antonie van Leeuwenhoek (1632-1723):-
> He was resident of Delft, Holland (Netherland).
> Animalcules:- He was the first person to observe and accurately describe microorganisms (bacteria and protozoa) called ‘animalcules’ (little animals) in 1676.
> Microscopes:- He constructed over 250 small powerful microscopes that could magnify around 50-300 times.
> He is considered as the:-
i. Father of microbiology
ii. Father of bacteriology
iii. Father of protozoology (protistology)
2. Louis Pasteur (1822 - 1895):-
> Louis Pasteur is known as the:-
i. Father of Modern Microbiology
ii. Father of Modern Bacteriology
> Fermentation:- He has proposed the principles of fermentation for the preservation of food.
> Sterilization technique:- He introduced sterilization techniques and developed steam sterilizers, hot air oven, and autoclave.
> Pateurization:- He described the method of pasteurization of milk.
> Vaccination:- He had also contributed for designing the vaccines against several diseases such as anthrax, fowl cholera, and rabies.
- Jenner’s experimental significance was realized by Pasteur who next applied this principle to the prevention of anthrax and it worked. He called the attenuated cultures vaccines (Vacca = cow) and the process as vaccination.
- Encouraged by the successful prevention of anthrax by vaccination, Pasteur marched ahead towards the service of humanity by making a vaccine for hydrophobia or rabies (a disease transmitted to people by bites of dogs and other animals).
- As with Jenner’s vaccination for small pox, principle of the preventive treatment of rabies also worked fully which laid the foundation of modern immunization programme against many dreaded diseases like diphtheria, tetanus, pertussis, polio and measles etc.
> Germ theory of disease:- 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 liquid nutrient medium to grow microorganisms, which is called as broth.
> Founder:- He was the founder of the Pasteur Institute, Paris.
3. Robert Koch (1843 - 1910):-
> He was a German physician and microbiologist.
> Solid media concept:- 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.
> Isolation of Bacteria:- He also introduced methods for isolation of bacteria in pure culture.
> Motility:- He described the hanging drop method for testing motility.
> Founder of Modern Bacteriology:- He discovered bacteria such as the anthrax bacilli, tubercle bacilli, and cholera bacilli. As the discoverer of the specific causative agents of deadly infectious diseases including tuberculosis, cholera, and anthrax, he is regarded as one of the main founders of modern bacteriology.
> Staining technique:- He 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.
> Koch’s postulates:- 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 micro-organisms 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 micro-organisms in pure culture from the lesions produced in the experimental animals.
Note:- An additional fifth criterion was introduced subsequently which states that antibodies 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 human diseases. There are some bacteria that do not satisfy all the four criteria of Koch’s postulates. Those organisms are:
i. Mycobacterium leprae and Treponema pallidum:- They cannot be grown in vitro; however can be maintained in animals.
ii. 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 the gene (coding for virulence) of a microorganism should satisfy all the criteria of Koch’s postulates rather than the microorganism itself.
4. Elie Metchnikoff (1845-1916):-
> He was a Russian zoologist best known for his pioneering research in immunology. He was a comparative zoologist from the village of Kharkov in modern-day Ukraine.
> Phagocytic theory:- He proposed the phagocytic theory of immunity in 1883.
> Cellular defense:- He is credited with first recognizing phagocytosis as an important cellular defense strategy.
> Innate immunity:- He discovered the process of phagocytosis and provided the initial descriptions of innate immunity. He confirmed that phagocytosis by neutrophils (“microcytes”) and macrophages was an essential part of the innate immune response in humans. He promulgated the idea of cell-mediated immunity as a defense against specific sets of microbial pathogens in 1884.
> Father:- He is called the father of cellular immunology for his studies on phagocytosis.
> Starfish study:- He reasoned that this highly advantageous host defense he observed in starfish mesenchymal cells would be found in higher species as well.
> WBC activity:- He discovered that some blood leukocytes, white blood cells (WBC) protect against disease by engulfing disease causing bacteria. These cells were called phagocytes and the process phagocytosis. Thus human blood cells also confer immunity, referred to as cellular immunity.
> Nobel Prize:- Metchnikoff and Ehrlich shared the Nobel Prize in 1908 for their descriptions of cellular and humoral immunity, respectively.
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