Discovery of Microbiology

 

Microbiology is the study of living organisms. The word "microbiology" was coined by French chemist Louis Pasteur. They are usually very small and not visible to the naked eye and require special techniques to isolate and grow.

Microorganisms are an organism that is microscopic and lacks highly differentiated cells and distinct tissues, which can only be seen under a microscope. The diverse groups of organisms include algae, archaea, bacteria, cyanobacteria, fungi, protozoa, and viruses. The bacteria and Archaea are procaryotic and have their genetic material located in a nucleoid. In unicellular eucaryotic organisms that lack cellular differentiation into tissues, cell differentiation is limited to cells involved in sexual reproduction, alternate vegetative morphology, or resting states such as cysts, including organisms, often referred to as algae, fungi, and protozoa.

Discovery of Microbiology and Contributors in Microbiology

Discovery Era 

Aristotle (384-322) and others believed that living organisms could develop from non-living materials. In the 13th century, Rogen Bacon described the disease caused by a minute “seed” or “germ.

In the 17th-century, English scientist Robert Hooke was use a lens to observe tiny units of tissue which he called “cells.

Anthony van Leeuwenhoek (1632-1723) Holland (Netherlands) was a Dutch linen merchant; he constructed a simple microscope composed of a double convex lens sandwiched between two silver plates. He designed more than 250 small and powerful microscopes capable of magnifying about 50-300 times. He was the first person to observe microorganisms (bacteria and protozoa) called "animalcules" (small animals) in 1676 and gave accurate descriptions of bacteria and protozoa using a microscope. Because of these outstanding contributions to microbiology, Anthony van Leeuwenhoek is considered the "Father of Microbiology". During 50 years (1674-1723) he wrote over 200 letters to the Royal Society in London.

 

Anthony van Leeuwenhoek (1632-1723)

Transitional Era

The debate on spontaneous generation has been resolved primarily by several experiments by Francesco Redi, John Needham, Lazzaro Spallanzani, Nicholas Appert, and others, and disease transmission research, which includes primarily the work of Ignaz Semmelweis and John Snow.

Francesco Redi, Italian physician (1626-1697): he was the first challenger to the ancient belief in spontaneous generation. He conducts a series of experiments with the decaying meat in three containers. One was open, the second was covered with paper, and the third was covered with a thin layer of gauze to keep flies out. The flies lay their eggs on the uncovered meat and the maggots developed. The other two pieces of meat did not spontaneously produce maggots. However, gauze-covered containers attracted flies and laid eggs in the gauze. These maggots are produced by egg.

Thus, the emergence of maggots from the decomposition of meat was due to the presence of fly eggs, and the meat did not spontaneously produce maggots as previously thought. Similar experiments by others have helped discredit the theory of larger organisms.

John Needham (1713-1781) reported experimental results on spontaneous generation. Needham boiled mutton broth, then sealed the flasks tightly and heated some flasks. Eventually, many flasks became cloudy, and still, microbes appeared on the mutton broth. He believed that organic matter contained a vital force that could confer the properties of life on the nonliving matter.

Lazzaro Spallanzani was an Italian naturalist (1729–1799): He attempted to improve on Needham's experiments and designs by sealing glass flasks containing water and seeds. He boiled the beef broth for a long time, removed the air from the flask, and sealed the flask. He proposed that air carried germs to the culture medium but also suggested that external air might be required for the growth of animals already in the medium. Thus Spallanzani disproved the doctrine of spontaneous generation.

Theodor Schwann (1810–1882) believed that the source of microorganisms was air and tried to prove this by passing air through a red-hot glass tube. Flasks remained sterile and free from microbes

George Schroeder and Theodor von Douche (1854) were the first proposed using cotton plugs to seal microbial culture tubes.

Golden Era

The Golden Era of microbiology began with the work of Louis Pasteur and Robert Koch, they have own research institute and their work was accepted by the scientific community and throughout the world.

Louis Pasteur (1822–1895): The concept of spontaneous generation was finally put to rest by the French chemist Louis Pasteur in an inspired set of experiments involving a swan neck flask. First filtered air through cotton and found that objects resembling plant spores had been trapped. If a piece of the cotton was placed in a sterile medium after the air had been filtered through it, microbial growth occurred. Next, he placed broth in a flask with a straight neck flask, heated their neck in a flame, and drew them out into a variety of curves while keeping the ends of the necks open and exposed to air allowing them to cool. No growth occurred when the contents of the flask were exposed to air. Pasteur pointed out that growth did not occur because the S-shaped flasks caught dust particles in the air and prevented them from entering the broth. By showing that air could enter into the flask, but not particles in the air, Pasteur proved that organisms grew on the dust in the broth.

Louis Pasteur is known as "the father of modern microbiology/father of bacteriology".

 

Louis Pasteur (1822–1895)

He refuted the spontaneous generation theory of disease and postulated a "germ theory of disease". He said the disease was not caused by bad air or vapor, but by microbes present in the air.

In 1858 Pasteur finally resolved the controversy of spontaneous generation versus biogenesis and proved that microorganisms do not spontaneously generate from inanimate matters, but arise from other microorganisms. He has proposed principles of food fermentation and preservation. Fermentation of fruits and grains to produce alcohol by microorganisms, and bacteria has been found to be responsible for spoiling wine during fermentation. He introduced sterilization technology and developed steam sterilizers, hot air ovens, and autoclaves. In 1862, Pasteur suggested that moderate heating at 62.8 °C (145 °F) for 30 minutes rather than boiling was sufficient to kill unwanted organisms without interfering with the product's flavor.  This process is called pasteurization.

In, English physicist John Tindall (1820–1893) conducted an experiment in a sterile box to prove that dust contained germs. He demonstrated that, in the absence of dust, sterile broth remains free of microbial growth indefinitely, even when directly exposed to air. He later discovered heat-tolerant bacteria known as endospore-forming bacteria. Long boiling or intermittent heating was required to kill these spores to completely sterilize the infusion, a process known as tyndallization.

 In, German physician Robert Koch worked to determine the cause of some animal diseases, first anthrax and then tuberculosis. He was the first to directly demonstrate the role of bacteria in disease. He isolated the first Bacillus anthracis (the causative agent of anthrax) in 1876. He perfected the technique of isolating bacteria into pure cultures. He introduced the use of a solid culture medium in 1881 using gelatin as a solidifying agent. He also described the hanging drop method for testing motility and introduced a staining method using aniline dye. In 1882 he discovered Mycobacterium tuberculosis.

The Koch Phenomenon: Robert Koch observed that guinea pigs already infected with Mycobacterium tuberculosis developed hypersensitivity reactions when injected with Mycobacterium tuberculosis or its proteins. This reaction is called the Koch phenomenon.

 

Robert Koch 

He proposed Koch postulate which was published in 1884, 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:

The microorganism should be constantly associated with the lesions of the disease. It should be possible to isolate the organism in pure culture from the lesions of the disease.

The same disease must result when the isolated microorganism is inoculated into a suitable laboratory animal.

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 antibodies to the causative organism should be demonstrable in the patient’s serum.

There are some bacteria that do not satisfy all four criteria of Koch's postulates. These organisms include:

Mycobacterium leprae and Treponema palladium: They cannot be grown in vitro, however, required animals for maintained

Neisseria gonorrhoeae: there is no animal model available; however, bacteria can be grown in vitro.

Fanne Eischemius Hesse (1850–1934) one of Koch's assistants was the first to suggest the use of agar in a culture medium. Agar-agar was superior to gelatin because it has a higher melting point (96°C) and solidifies than gelatin (40-45°C) and was not attacked by most bacteria.

Another of Koch's assistants, Richard Petri, developed the Petri dish (dish) used for solid culture media in 1887.

Thus the contribution of Robert Koch, Fannie Hesse, and Richard Petri made possible the isolation of pure cultures of microorganisms and directly stimulated progress in all areas of microbiology.

Development of Vaccines

Vaccination was discovered before germ theory, but it wasn’t fully understood until the time of Pasteur. In the late 18th century, milkmaids who contracted the nonlethal cowpox sickness from the cows they were milking were spared in deadly smallpox outbreaks that ravaged England periodically.

English physician Edward Jenner (1749-1823) was the first to discover a vaccine to prevent smallpox. He was impressed by the observation that countryside milkmaids who contracted cowpox (Cowpox is a milder disease caused by a virus closely related to smallpox) while milking were subsequently immune to smallpox. On May 14, 1796, he proved that smallpox could be prevented by vaccinating persons with pus from cowpox lesions. This process eventually became known as vaccination, and the use of the virus to protect against smallpox in humans became popular.

Scottish physician and bacteriologist Alexander Fleming first discovered the "miracle drug" penicillin in 1929. He had been experimenting with something that killed pathogens ever since he studied wound infections during World War I (1914-1918).  Solid bacterial culture Petri dish was leaving to longer than usual. Like any unused food source, it grew moldy and fluffy mold. The colonies in the area around the fungal colony were smaller and did not seem to grow well compared to the bacteria in the rest of the dish. The compound responsible for this antibacterial action was named penicillin. Penicillin, the first antibiotic, was later used to prevent bacterial infections and treat people suffering from various bacterial infections.

Waxman discovered in 1944 discovered antibiotic streptomycin, produced by two strains of Actinomycetes, Streptomyces griseus. Waxman received the Nobel Prize in 1952 for his discovery of streptomycin used to treat tuberculosis.

Modern Era

By the end of 1900, microbiology had reached its teens and microbes had become ideal tools for studying various life processes. Thus, independent disciplines of microbiology and molecular biology were born.

The relative simplicity, short life span and genetic homogeneity of microbes provided a powerful model for understanding the physiological, biochemical and genetic complexities of living organisms.

The field of molecular biology has made great strides in understanding the genetic code, how DNA is regulated, and how RNA is translated into protein. Until now, research has mainly focused on plant and animal cells, which are much more complex than bacterial cells. When researchers turned to study these processes in bacteria, many of the secrets of genes and enzymes began to be revealed.

Other important contributors

Joseph Lister: He is considered the father of antiseptic surgery. He used carbonic acid during his surgery.

Hans Christian Gram: He developed "Gram's stain".

Ernst Ruska: He is the founder of the electron microscope.

Kleinberger: He explained the existence of L-type bacteria.

Barbara McClintock: She explained transposons.

Walter Gilbert and Frederick Sanger: Pioneering (1977) DNA sequencing methods.

Ferdinand Cohn (1828–1898) discovered the existence of heat-resistant bacterial endospores.

Karry B Mullis: Discovered polymerase chain reaction (PCR).

Elie Metchnikoff (1845-1916) proposed the phagocytic theory of immunity in 1883.

Charles Louis Alphonse Laveran (1845–1922): Discoverer of the Malaria Parasite.

Martinus Willem Beijerinck (1851–1931): Pioneer of General Microbiology.

Stanley Falkow: Proposed Molecular Koch’s postulates, a modification of Koch’s postulates.

Walter Reed (1851–1902): Yellow Fever Fighter.

Erwin F Smith (1854–1927): Father of Plant Pathology.

David Bruce (1855–1931): Pioneer of Veterinary Microbiology.

Kitasato Shibasaburo (1853–1931): First to Isolate Clostridium tetani and a Pioneer of Serology.

Albert Leon Charles Calmette (1863–1933): Antituberculosis and BCG Vaccination.

Howard Taylor Ricketts (1871–1910): Pioneer of Rickettsial Diseases Studies.

Oswald Theodore Avery (1877–1955): Microbiological Genetic Transmission and DNA.

William C Frazier (1894–1991): Pioneer of Dairy and Food Microbiologist.

Ira Lawrence Baldwin (1895–1999): Pioneer of Agricultural Microbiology and Education.

Lederberg (1922–2006): Transduction and Replica Plating.

References

1.    Trivedi P.C., Pandey S. & Bhadauriya S. (2010). Microbiology Textbook. Index Publisher First Edition.

2.    Prescott, Harley, and Klein’s., (2008) Microbiology Textbook, Index Publisher Seventh Edition.