Contributors in microbiology

Contents

• Antony van Leeuwenhoek (1632–1723)
• Edward Jenner (1749–1823)
• Louis Pasteur (1822–1895)
• Robert Koch (1843–1912)
• Iwanowsky & Beijerinck (Early Virology)
• Alexander Fleming (1881–1955)
• Selman Waksman (1888–1973)

Antony van Leeuwenhoek (1632–1723)

Antony van Leeuwenhoek, a draper from Delft in Holland, ground his own lenses and built simple microscopes as a hobby. His single-lens instruments achieved magnifications of 200–300×. By examining samples of rainwater, pond water, and scrapings from his own teeth, he observed tiny moving creatures he called “little animalcules.” These were the first descriptions of protozoa, bacteria, and yeasts. He meticulously sketched his observations and communicated them to the Royal Society of London, earning recognition as the first person to visualize the microbial world.

Edward Jenner (1749–1823)

Edward Jenner was an English country physician who noticed that milkmaids who had contracted cowpox never developed smallpox. In 1796, he deliberately inoculated an eight-year-old boy with material from a cowpox lesion and later showed the boy was protected from smallpox. His 1798 pamphlet, An Inquiry into the Causes and Effects of the Variolae Vaccinae, described this method. In recognition, Louis Pasteur later coined the term “vaccine” (from Latin vacca, meaning cow).

Louis Pasteur (1822–1895)

Louis Pasteur, professor of chemistry at the University of Lille, is often called the “Father of Microbiology.” He disproved spontaneous generation by demonstrating biogenesis with swan-necked flasks.

Fermentation & Pasteurization

He showed that undesirable microbes spoil wine and beer, while yeasts produce alcohol. Heating to 50–60 °C for a few minutes—now known as pasteurization—kills harmful organisms in milk and other beverages.

Germ Theory & Sterilization

Pasteur was a founding advocate of the germ theory of disease. He designed the steam sterilizer (autoclave), hot-air oven, and promoted cotton wool plugs to protect culture media. He coined “anaerobic” for microbes that grow without oxygen.

Vaccines & Attenuation

• Silkworm Disease (Pebrine): Showed protozoan cause and controlled infection by selecting healthy larvae.
• Chicken Cholera: Discovered attenuation—cultures weakened by aging no longer killed fowl. This principle underlies live vaccines.
• Anthrax: Cultivated Bacillus anthracis in sterile media, demonstrated disease transmission, and developed an attenuated vaccine.
• Rabies: Developed the first rabies vaccine by serially passing virus through rabbit brains then drying spinal cord tissues. The Pasteur Institute was founded in 1888 for mass treatment.

Robert Koch (1843–1912)

Robert Koch, a German physician, is the “Father of Practical Bacteriology.” He isolated the anthrax bacillus from infected animals, grew it in pure culture, observed spore formation, and reproduced the disease in mice. He refined techniques for staining and prepared smear slides for better microscopy.

Major Contributions

• Anthrax & Spores: Tracked life history and spore resilience; passed cultures through twenty rodent generations.
• Staining Methods: Introduced aniline dyes to visualize bacteria on glass slides.
• Tuberculosis: Discovered Mycobacterium tuberculosis, reproducing the disease in animals and fulfilling Koch’s postulates.
• Cholera: Identified Vibrio cholerae, the cholera bacterium.
• Pure Cultures: Adopted agar from seaweed (courtesy of Hesse), which solidifies at 45 °C and melts at 90 °C, revolutionizing bacterial cultivation.
• Old Tuberculin & Koch Phenomenon: Noted localized immune reaction in infected animals; developed the tuberculin skin test.

Koch’s Postulates

1. A specific organism must be found in every case of the disease.
2. The organism must be isolated and grown in pure culture.
3. Inoculation of the pure culture into a healthy host reproduces the disease.
4. The organism must be re-isolated from the experimentally infected host.
5. Detection of specific antibodies in patient serum confirms the causal agent.

Early Virology: Iwanowsky & Beijerinck

In 1892, Dmitri Iwanowsky filtered sap from tobacco mosaic–infected leaves through a porcelain filter that trapped bacteria. The filtered sap remained infectious, proving a submicroscopic agent. Six years later, Martinus Beijerinck suggested it was a “contagium vivum fluidum” (infectious living fluid) and coined the term virus. In 1935, Wendell Stanley crystallized the tobacco mosaic virus, showing it behaved like a chemical substance.

Alexander Fleming (1881–1955)

At St. Mary’s Hospital in London, Fleming discovered lysozyme (an enzyme in saliva and tears that lyses bacteria). In 1928, he noticed that a Penicillium notatum mold contaminating his staphylococci cultures produced clear zones where bacteria could not grow. He isolated the active agent—penicillin—in solution. Later, Howard Florey and Ernst Chain purified it and demonstrated its curative power in animals and humans. Fleming, Florey, and Chain shared the 1945 Nobel Prize in Physiology or Medicine for this breakthrough.

Selman Waksman (1888–1973)

Selman Waksman, a Ukrainian-born American at Rutgers University, led a search for soil-derived antibiotics. He and his team discovered streptomycin (the first effective anti-tuberculosis drug) and neomycin, among others. Waksman coined the term antibiotic and received the 1952 Nobel Prize. He also contributed to enzyme detergents, anti-fouling marine coatings, and fungal disease control in grapes.