Microbiology Study Guide

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Microbiology Study Guide

• The idea that living things spontaneously
  generate was proven false by Pasteur
• Microbes include bacteria, viruses, and yeasts
• Scientists used microscopes and experimental
  evidence to develop
• Cell theory
• Germ theory
• Today vaccination and antibiotics are used to
  fight microbial diseases

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Spontaneous Generation theory

• The idea that living things can naturally appear
  from non-living matter
• Examples
• Flies from dead meat
• Frogs from mud

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Francesco Redi

• 1668
• Experiment with flies and rotting meat

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Redis Observations

• Jar left open? flies grow
• Jar sealed? no flies grow
• Opponents argued that the sealed jar locked out a
  vital force in the air
• Jar covered with cloth? flies attracted by smell
  but no flies grow in meat

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Antonio Spallanzani

• 1700s
• Experiment with boiled and unboiled flasks of
  broth
• If boiled and then sealed, the broth does not
  spoil
• If boiled and left open, then broth spoils
• Conclusion living organisms that cause broth to
  spoil do not spontaneously generate

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Biogenesis Theory

• Cells can only come from pre-existing cells
• Part of the cell theory
• Cells are the smallest units of life
• All living things contain at least one cell
• Cells can only arise from pre-existing cells

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The discovery of bacteria

• Bacteria cannot be observed without a microscope
• People once believed bacteria could spontaneously
  generate
• Observed them in spoiling food
• Contaminate everything

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Louis Pasteur and the germ theory

• 1800s
• Pasteur proved that yeasts cause wine to ferment
• Yeasts are microscopic fungi
• Bacterial growth instead of yeast can spoil wine

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Pasteurss Experiment proving spontaneous
generation false

• Used swan necked flasks that trapped dust and
  dirt contaminated with bacteria
• Showed that sterilized (pasteurized) broth will
  not spoil if kept clean
• Bacteria in air cause food to spoil
• Bacteria cannot spontaneously generate
• Proved biogenesis true

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Pasteur theorized that contagious diseases are
caused by microbes like bacteria

• Spread from person to person
• Can be killed using pasteurization (heat)
• Led to improved sanitation
• Food preservation
• Healthcare
• Sewage and garbage removal

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The Germ Theory

• Micro-organisms cause some diseases
• These micro-organisms do not spontaneously
  generate, but instead
• Are spread from person to person
• Through the air
• In contaminated food
• In contaminated water
• Via physical contact

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The discovery of viruses

• Viruses are 10 to 100 times smaller than bacteria
• Viruses are obligate parasites
• Cannot reproduce on their own
• Have no metabolism of their own
• Are not cellular
• Viruses were discovered by accident
• Scientists looking for a very small bacterium
• Virus means poison

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Viruses vs Bacteria
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Virus Particle Structure
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Bacterial Cell Structure
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Types of bacterial cells

• Bacilli are rod shaped
• E. coli
• Salmonella
• Cocci are spherical
• Streptococcus
• Staphylococcus
• Spirilli are helical/twisted
• Lyme disease bacteria

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Antibiotics kill bacteria but are harmless to
eukaryote cells

• Antibiotics attack a bacterial cell wall
  component not found in eukaryotes
• Can be given internally
• Do not harm human or animal cells
• Disinfectants kill ALL living cells
• Cannot be given internally
• Examples
• Iodine
• Bleach
• soap

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Discovery of Antibiotics

• 1880s
• Alexander Fleming discovered penicillin
  accidentally
• Was growing bacteria in petri dishes
• Mold spore contaminated dish
• Clear zone developed around mold
• Isolated penicillin produced by mold
• Mold makes penicillin to outcompete bacteria for
  food

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Vaccination

• Edward Jenner 1760s
• Showed that smallpox could be prevented
• Infected boy with cowpox
• Cowpox infection produced
• immunity from smallpox

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Human Disease Project

• Follow directions and make two pamphlets
  explaining your assigned bacteria and your
  assigned virus.
• Accuracy, completeness, and neatness count