Humans and the Microbial
World
A Glimpse of History
Science of microbiology born in 1674
Antony van Leeuwenhoek (1632–1723)
• Made simple magnifying glass
• Studied lake water
• Observed ‘animalcules’
Robert Hooke
• Also credited with discovery
• Described ‘microscopical mushroom’ (common bread mold) in 1665
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Importance of Microorganisms
Microorganisms are foundation for all life on earth
Have existed for ~3.5 billion years
Plants, animals, modern microorganisms all evolved from ancestral bacteria Our life depends on their activities
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The Dispute Over Spontaneous Generation
Theory of Spontaneous Generation
• “Life arises spontaneously from non-living material”
• Theory had supporters and detractors
• Detractors included
– Francesco Redi
– Louis Pasteur
– John Tyndall
• Each contributed to disproving the theory
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The Dispute Over Spontaneous Generation
Italian biologist and physician Francesco Redi
Demonstrated worms on rotting meat came from eggs of flies landing on meat (1668)
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Placed meat in two jars
Covered one jar with gauze
Gauze prevented flies from depositing eggs
No eggs no worms
Took another 200 years to convincingly disprove spontaneous generation of microorganisms
• One reason: conflicting results between laboratories
The Dispute Over Spontaneous Generation
Multiple contributions helped define
Some labs demonstrated boiled broths still produced microorganisms
Other labs contradicted their results
• Boiled broths longer; sealed flasks by melting necks
• Broths remained sterile unless neck cracked
Controversy still unsolved
• Some argued heating destroyed “vital force” necessary for spontaneous generation
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The Dispute Over Spontaneous