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History of Microbiology - 80:20 High-Yield Summary

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1. The Pre-Microscopic Era (before 1650)

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2. The Microscopy Revolution (1665-1700)

Robert Hooke (1665)

• Wrote Micrographia - used compound microscopes to observe thin cork slices
• Coined the term "cell" (because spaces resembled honeycomb cells)
• Did NOT observe living microorganisms himself

Antoni van Leeuwenhoek (1670s-1680s) ★ MOST TESTED

• Dutch fabric merchant; self-taught microscope builder
• Built single-lens microscopes with far higher magnification than any compound scope at the time
• First to observe and describe bacteria, protozoa, red blood cells, and sperm - called them "animalcules"
• Reported findings to the Royal Society of London
• "Father of Microbiology" / Father of Bacteriology

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3. Spontaneous Generation vs. Biogenesis (1668-1861)

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4. Louis Pasteur (1822-1895) ★★ HIGHEST YIELD

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5. Robert Koch (1843-1910) ★★ HIGHEST YIELD

Koch's Postulates (memorize all 4) ★

1. The organism must be found in all cases of the disease and its distribution must match the lesions
2. The organism must be grown in pure culture in vitro for several generations
3. The pure culture, when inoculated into a susceptible animal, must produce the typical disease
4. The organism must be re-isolated from the experimentally produced disease

Limitations of Koch's Postulates

• Cannot apply to organisms that cannot be cultured (e.g., Treponema pallidum, Mycobacterium leprae)
• Cannot apply when there is no animal model (e.g., Neisseria gonorrhoeae)
• Does not account for asymptomatic carriers or opportunistic pathogens
• Led to Molecular Koch's Postulates (Falkow, 1988) - for virulence genes, not just organisms

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6. Ignaz Semmelweis (1847) ★

• Austrian obstetrician
• Showed that puerperal (childbed) fever dropped dramatically when doctors washed hands with chlorinated lime solution before delivering babies
• Incidence fell from >10% to <2%
• Was ridiculed and rejected by the medical establishment - died in a psychiatric institution in 1865
• Precursor to germ theory - proved handwashing saves lives before anyone understood why

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7. Joseph Lister (1867) ★

• Inspired by Pasteur's germ theory
• Introduced carbolic acid (phenol) spray in the operating theatre - antiseptic surgery
• Dramatically reduced post-surgical infection and gangrene rates
• "Father of Antiseptic Surgery"
• Distinction: Lister = antisepsis (killing organisms in the field); later replaced by Semmelweis-inspired asepsis (keeping organisms out)

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8. Edward Jenner (1796) ★

• English physician
• Observed that milkmaids who got cowpox were immune to smallpox
• Inoculated 8-year-old James Phipps with cowpox material, then challenged him with smallpox - he did not develop smallpox
• Created the world's first vaccine (vacca = Latin for cow)
• Preceded Pasteur and germ theory by ~80 years - Jenner did not know why it worked
• Led ultimately to the eradication of smallpox in 1980

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9. Alexander Fleming (1928) ★★

• Scottish bacteriologist
• Discovered that a mold (Penicillium notatum) contaminating a Staphylococcus culture had killed the surrounding bacteria
• Named the active substance penicillin
• Did not purify it; Florey and Chain (1940-1941) purified penicillin and showed its clinical efficacy
• Fleming, Florey, and Chain shared the Nobel Prize in 1945
• Discovery of the first antibiotic - changed medicine permanently

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10. Other High-Yield Names (Know the association)

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11. Molecular Koch's Postulates (Falkow, 1988) - Modern Update

1. The virulence property (phenotype) should be significantly associated with pathogenic strains, not non-pathogenic ones
2. Inactivation of the virulence gene should reduce pathogenicity
3. Reversion/replacement of the mutated gene with wild-type should restore virulence

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The 80:20 Cheat Sheet

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