History of Microbiology

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History of Microbiology

• Nature of Science
• Early Observations
• Spontaneous Generation Controversy
• Germ Theory of Disease

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Nature of Science

• Science is systematized knowledge developed
  through the application of the scientific method
• Scientific method
• Observations (objective vs. subjective)
• Formulate hypothesis
• Test hypothesis with controlled experiments
• Accept, revise or reject hypothesis

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Early Observations Experiments

• Microscopes
• van Leeuwenhoek Hooke
• Spontaneous Generation Controversy
• Germ Theory of Disease Robert Koch

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Spontaneous Generation

• Biogenesis vs. Abiogenesis
• Aristotle
• Jan Baptista van Helmont (1580-1644)
• Francisco Redi (1626-1697)
• John T. Needham (1713-1781)
• Lazzaro Spallanzani (1729-1799)
• Theodor Schwann (1810-1882)
• Louis Pasteur (1822-1895)

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Biogenesis vs. Abiogenesis

• Biogenesis - development of life from preceding
  life forms
• Abiogenesis - life arises from inorganic or
  non-living materials

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Aristotle

• first to record possible routes to life.
• He saw beings as arising in one of three ways,
  from sexual reproduction, asexual reproduction or
  nonliving matter.
• observable that aphids arise from the dew on
  plants, fleas from putrid matter, and mice from
  dirty hay
• this belief remained unchallenged for more than
  two thousand years.

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Jan Baptista van Helmont (1580-1644)

• Reported in late 1500s that barley grains and
  old shirts left in a corner would spontaneously
  give rise to mice
• Claimed as evidence that supported spontaneous
  generation or abiogenesis

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Francisco Redi (1626-1697)

• Set up controlled experiment to test idea of
  spontaneous generation with respect to maggots
  appearing on rotting meat
• open jar with meat
• screened jar with meat
• sealed jar with meat

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von Helmut
open
screened
sealed
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John T. Needham (1713-1781)

• Flies do not arise spontaneously but the
  animalcules described by van Leeuwenhoek must
• In 1748 Needham boiled mutton broth, stoppered
  and noted that flask becam turbid
• Argued that the turbidity, which included many
  animalcules must have arisen spontaneously

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Lazzaro Spallanzani (1729-1799)

• Repeated Needhams experiments
• Used flasks that were sealed by melting the glass
  rather than with a cork
• Found that if sealed properly, flasks boiled 45
  minutes would remain sterile thus refuting
  Needhams conclusions

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Theodor Schwann (1810-1882)

• An argument against Spallanzani experiments is
  that they excluded air
• Constructed apparatus to sterilize air coming
  into flask
• Results supported biogenesis

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Theodor Schwann (1810-1882)

• Apparatus used by Schwann The central flask,
  which is being rendered sterile by heating
  contains the infusion. Air is passed through it
  from the heated coil on right. The flask at left
  is a mercury trap through which air escapes after
  passing through the central flask.

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Louis Pasteur (1822-1895)

• Looked at air which had been filtered
• Developed swan neck flask to deal with heated air
  problem
• Looked at frequency of occurrence of contaminated
  flasks
• Settled controversy

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Louis Pasteur (1822-1895)

• An example of the swan-necked flask

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Germ Theory of Disease

• Observation on causative agents of potato blight
  and diseases of silkworms led to hypothesis
• Formalized through work of Pasteur and Koch (and
  others) led to theory that germs or
  microorganisms may cause disease

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Germ Theory of Disease

• Robert Koch first developed relationship between
  microorganisms and disease
• Developed Kochs Postulates for testing
  relationship
• Discovered cause of anthrax and tuberculosis

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Germ Theory of Disease

• Kochs Postulates
• Same microorganism must be observed in every
  instance of disease
• Organism must be isolated from diseased host and
  grown in pure culture
• Specific disease must be reproduced when pure
  culture is reintroduced into host