CONTRIBUTIONS OF SCIENTISTS IN MICROBIOLOGY
LOUIS PASTEUR (1822-95)
- Originally trained as a chemist
- His studies on fermentation led him to take interest in microorganisms
- His discoveries revolutionized medical practice, although he never studied medicine.
- Louis Pasteur is known as “Father of microbiology” because his contribution led to the development of microbiology as a separate scientific discipline.
CONTRIBUTION OF LOUIS PASTEUR :
- Coined the term microbiology: for the study of living organisms of microscopic size.
- Proposed germ theory of disease: putrefaction and fermentation was the result of microbial activity and that different types of fermentations were associated with different types of microoganisms (1857).
- Disapproved theory of spontaneous generation: He disapproved the theory of spontaneous generation in 1860-61.
- Developed sterilization techniques : Introduced sterilization techniques and developed the steam sterilizer, hot-air oven and autoclave in the course of these studies.
- Developed methods and techniques for cultivation of microorganisms: for successful cultivation it was necessary to discover a suitable growth medium and to establish optimal conditions of temperature, acidity or alkalinity, and oxygen tension.
- Studies on pebrine (silk worm disease), anthrax, chicken cholera and hydrophobia
- Pasteurization: The process of destroying bacteria, known as pasteurization (1863-65). This process (pasteurization) is employed to preserve milk and certain other perishable foods throughout the civilized world today.
- Coined the term vaccine: Pasteur who coined the term vaccine for such prophylactic preparations to commemorate the first of such preparations namely cowpox, employed by Jenner for protection against smallpox.
- Discovery of attenuation and chicken cholera vaccine : An accidental observation that chicken cholera bacillus cultures left on the bench for several weeks lost their pathogenic, property but retained their ability to protect the birds against subsequent infection by them, led to the discovery of the process of attenuation and the development of live vaccines.
- Developed live attenuated anthrax vaccine: The attenuated cultures of the anthrax bacillus by incubation at high temperature (42-43°C) and proved that inoculation of such cultures in animals induced specific protection against anthrax.
- Developed rabies vaccine : Developed rabies vaccine in 1885.He did not know that rabies was caused by a virus, but he managed to develop a live attenuated vaccine for the disease.
- Noticed Pneumococci: Pneumococci were first noticed by Pasteur and Sternberg independently in 1881.
PAUL EHRLICH (1854-1915)
An outstanding German Scientist and genius of extraordinary activity also known as “Father of Chemotherapy”.
CONTRIBUTION OF PAUL EHRLICH :
- Stains to cells and tissues: He applied stains to cells and tissues for the purpose of revealing their function.
Acid-fastness of tubercle bacillus: He reported the acid-fastness of tubercle bacillus.
Methods of standardizing toxin and antitoxin: He introduced methods of standardizing toxin and antitoxin and coined the term minimum lethal dose.
Side chain theory of antibody production: He proposed side chain theory of antibody production.
Salvarsan introduction: He discovered salvarsan, an arsenical compound(arsphenamine), sometimes called the ‘Magic Bullet’ was capable of destroying the spirochete of syphilis with only moderate toxic effects. He continued his experimentation and in 1912 he announced the discovery of neosalvarsan. Thus he created a new branch of medicine known as Chemotherapy, he was given the title ‘Father of Chemotherapy’
JOSEPH LISTER (1827-1912)
- Was a professor of Surgery in Glasgow Royal Infirmary.
- Fond of Pasteur’s study on microorganisms involvement in fermentation and putrefaction.
- He is known as “Father of Modern Surgery”.
CONTRIBUTION OF JOSEPH LISTER :
- Developed a system of antiseptic surgery-Developed a system of antiseptic surgery to prevent microorganisms from entering wounds. After Lister published his findings in 1867, his approach was remarkably successful and transformed the field of surgery. Provided strong evidence for the role of microorganism in disease because phenol, which has ability to kill bacteria, can also prevented wound infections.
- Father of modern surgery-He established the guiding principle of antisepsis for good surgical practice and was milestone in the evolution of surgical practice from the era of ‘laudable pus’ to modern aseptic techniques. For this work he is called the “Father of modern surgery”.
ANTONY VAN LEEUWENHOEK (1632-1723)
- The 1st person who observe and report bacteria (1673) using a simple microscope was an amateur microscopist Antony van Leeuwenhoek.
- Was a draper and haberdasher in Delft, Holland.
- He spent most his time with lenses and observing diverse materials through them.
- In 1683 he made accurate descriptions of various types of bacteria.
- Later he communicated them to the Royal Society of London.
- Their importance in medicine and in other areas of biology became recognizable after two centuries.
CONTRIBUTION OF ANTONY VAN LEEUWENHOEK :
- He constructed the first microscope: Consists of a single biconvex lens that magnified about x200.
- The first person to observe microorganisms: Microorganisms were first seen by Antony van Leeuwenhoek (1673) and he found many microorganisms in materials such as water, mud, saliva and the intestinal contents of healthy subjects, and he recognized them as living creatures (animalcules) and to Leeuwenhoek the world of “little animalcules” represented only a curiosity of nature.
- Accurate description of bacteria: He first accurately described the different shapes of bacteria as cocci (spheres), bacilli (rods) and spirochetes (spiral filaments) and communicated them to Royal Society of London in 1683.
ROBERT KOCH (1843-1910)
- Was German physician.
- 1st direct demonstration of the role of bacteria in carrying disease came by the study of anthrax by Koch.
- Winner of the Nobel Prize in 1905.
- Robert Koch is known as “Father of bacteriology”
CONTRIBUTIONS OF ROBERT KOCH :
- Staining techniques: He described methods for the easy microscopic examination of bacteria in dried, fixed films stained with aniline dyes (1877).
Hanging drop method: He was the first to use hanging drop method by studying bacterial motility.
Methods for isolating pure cultures of bacteria: He devised a simple method for isolating pure cultures of bacteria by plating out mixed material on a solid culture medium and to isolate pure cultures of pathogens.
Discoveries of the causal agents of anthrax (1876), tuberculosis (1882), and cholera (1883).
- Koch’s phenomenon: Koch (1890) observed that a guinea pig already infected with the bacillus responded with an exaggerated response when injected with the tubercle bacillus or its protein.
This hypersensitivity reaction is known as Koch’s phenomenon.
KOCH’S POSTULATES:
- Series of guidelines for the experimental study of infectious disease.
- According to these, a microorganism can be accepted as the causative agent of an infectious disease only if the following conditions are satisfied:
Postulate 1: The organism should be regularly found in the lesions of the disease.
Postulate 2: It should be possible to isolate the organism in pure culture from the lesions.
Postulate 3: Inoculation of the pure culture into suitable laboratory animals should reproduce the lesion of the disease.
Postulate 4: It should be possible to reisolate the organism in pure culture from the lesions produced in the experimental animals.
✴️The specific antibodies to the bacterium should be demonstrable in the serum of patient suffering from the disease. This was an additional criterion that was introduced subsequently
EXCEPTION : Most of the human bacterial pathogens satisfy Koch’s postulates except for those of Mycobacterium leprae and Treponema pallidum, the causative agent of leprosy and syphilis, respectively. Both these bacteria are yet to be grown in cell-free culture media.