History, Scope and Classification of Microbiology
Domain 1 examines the historical experiments that established microbiology and the systems used to classify microbes. Questions often ask who proved what, how binomial names are written, and why viruses are excluded from cellular classification.
Core rules and concepts
- Leeuwenhoek first described bacteria and protozoa using single-lens microscopes; Pasteur used swan-neck flasks to disprove spontaneous generation and introduced pasteurization.
- Koch linked Bacillus anthracis and Mycobacterium tuberculosis to disease and formulated postulates: the organism must be found in diseased hosts, be isolated in pure culture, reproduce disease when inoculated, and be re-isolated.
- Jenner used cowpox material for smallpox protection; Fleming discovered penicillin from Penicillium; Waksman isolated streptomycin from soil actinomycetes.
- Woese's three domains are Bacteria, Archaea and Eukarya; Whittaker's five kingdoms are Monera, Protista, Fungi, Plantae and Animalia. Bergey's Manual is the standard reference for bacterial taxonomy.
- Binomial nomenclature: genus capitalized, species lowercase, both italicized in print or underlined by hand.
Worked example
A sterile broth in a sealed flask stays clear, while the same broth in an open swan-neck flask also stays clear until the neck is broken. Reasoning: dust and microbes from air enter only after the neck breaks; the clear unbroken flask does not generate life spontaneously. This is Pasteur's evidence against spontaneous generation, not Koch's postulates.
Mark-losing traps
- Do not credit Pasteur with discovering penicillin or Koch with pasteurization.
- Viruses are acellular and are not classified in the three domains; they are placed by genome and structure.
- Writing "escherichia Coli" is wrong; the correct form is Escherichia coli.
- Archaea are not a subgroup of bacteria; their cell walls lack peptidoglycan and their membrane lipids differ.