Transcript 4 - History of Microbiology

History of Microbiology
Nature of Science
Early Observations
Spontaneous Generation Controversy
Germ Theory of Disease
Nature of Science
• Science is systematized knowledge
developed through the application of the
scientific method
• Scientific method
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Observations (objective vs. subjective)
Formulate hypothesis
Test hypothesis with controlled experiments
Accept, revise or reject hypothesis
Early Observations &
Experiments
• Microscopes
– van Leeuwenhoek & Hooke
• Spontaneous Generation Controversy
• Germ Theory of Disease & Robert Koch
Spontaneous Generation
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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)
Biogenesis vs. Abiogenesis
• Biogenesis - development of life from
preceding life forms
• Abiogenesis - life arises from inorganic or
non-living materials
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.
Jan Baptista van Helmont
(1580-1644)
• Reported in late 1500’s 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
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
open
von Helmut
screened
sealed
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
Lazzaro Spallanzani (1729-1799)
• Repeated Needham’s 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 Needham’s conclusions
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
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.
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
Louis Pasteur (1822-1895)
• An example of the
swan-necked flask
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
Germ Theory of Disease
• Robert Koch first
developed relationship
between
microorganisms and
disease
• Developed Koch’s
Postulates for testing
relationship
• Discovered cause of
anthrax and
tuberculosis
Germ Theory of Disease
• Koch’s 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