Microbiology

1
Microbiology

• Brief Review
• Spontaneous Generation and Biogenesis

2
What is Microbiology?
Microbes, or microorganisms are minute living
things that are usually unable to be viewed with
the naked eye.
What are some examples of microbes?
Bacteria, fungi, protozoa, algae, viruses are
examples!

• Some are pathogenic
• Germ refers to a rapidly growing cell.

3
Review
What is Microbiology?

• Microbes
• Decompose organic waste
• Are producers in the ecosystem by photosynthesis
• Produce industrial chemicals such as ethyl
  alcohol and acetone
• Produce fermented foods such as vinegar,
  cheese, and bread

4
What is Microbiology?
Knowledge of Microbes allows humans to Prevent
food spoilage Prevent disease occurrence Led to
aseptic techniques to prevent contamination in
medicine and in microbiology laboratories.
5
History of Microbiology
Ancestors of bacteria were the first life on
Earth.
6
Discovery of Microorganisms

• Antony van Leeuwenhoek (1632-1723)
• First person to observe and describe
  micro-organisms accurately
• Teeth scrapings, pond water

Figure 1.1b
7
Van Leeuwenhoek 1684
8
Biogenesis vs. Spontaneous Generation
Two hypotheses The hypothesis that living
organisms arise from nonliving matter is called
spontaneous generation. According to spontaneous
generation, a vital force forms life. The
Alternative hypothesis, that the living organisms
arise from preexisting life, is called
biogenesis. (Rudolf Virchow)
9
The Conflict over Spontaneous Generation

• Spontaneous Generation
• living organisms can develop from nonliving or
  decomposing matter
• Francesco Redi (1626-1697)
• disproved spontaneous generation for large
  animals
• showed that maggots on decaying meat came from
  fly eggs

10
History of Microbiology
Redi filled six jars with decaying meat.
Conditions Results
3 jars covered with fine net No maggots
3 open jars Maggots appeared
From where did the maggots come? What was the purpose of the sealed jars? Spontaneous generation or biogenesis? From where did the maggots come? What was the purpose of the sealed jars? Spontaneous generation or biogenesis?
11
But could spontaneous generation be true for
microorganisms?

• John Needham (1713-1781)
• his experiment
• mutton broth in flasks ? boiled, allowed to cool
  ?sealed
• results broth became cloudy and contained
  microorganisms
• Lazzaro Spallanzani (1729-1799)
• his experiment
• broth in flasks ?sealed ? boiled
• results no growth of microorganisms
• What about ability of air to generate life? It
  was not allowed to enter
• Critics claimed he killed the vital force

12
Louis Pasteur (1822-1895)

• His experiments
• placed nutrient solution in flasks
• created flasks with long, curved necks
• boiled the solutions
• left flasks exposed to air
• results no growth of microorganisms

Figure 1.3
13
History of Microbiology
1861 Louis Pasteur demonstrated that
microorganisms are present in the air.
Conditions Results
Nutrient broth placed in flask, heated, not sealed Microbial growth
Nutrient broth placed in flask, heated, then sealed No microbial growth
Spontaneous generation or biogenesis? Spontaneous generation or biogenesis?
14
Final blow to theory of spontaneous generation

• John Tyndall (1820-1893)
• demonstrated that dust carries microorganisms
• showed that if dust was absent, nutrient broths
  remained sterile, even if directly exposed to air
• also provided evidence for the existence of
  exceptionally heat-resistant forms of bacteria