Humans and the Microbial World

Chapter 1
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