1. The first microbes were observed in 1673.
Chapter 1
History of Microbiology
The first microbes were observed in 1673.
In 1665, Robert Hooke (Englishman) reported that living things were composed of little boxes or cells.

2. Chapter 1
History of Microbiology
, Antoni van Leeuwenhoek (Dutch) described live microorganisms that he observed in teeth scrapings, rain water, and peppercorn infusions.

3. Many believed spontaneous generation:
Chapter 1
History of Microbiology
Many believed spontaneous generation:
life can arise from non-living matter
In 1668, the Italian physician Francesco Redi performed an experiment to disprove spontaneous generation.
Can you think of an experiment that could disprove spontaneous generation?

4. CAN LIFE ARISE FROM NON LIFE
CAN LIFE ARISE FROM NON LIFE? People believed for thousands of years that live maggots could be spawned from dead meat. In 1665, Francesco Redi (1626–1697) put meat in three jars, one open, one closed with gauze and the third closed with paper. Flies laid their eggs on the meat in the open jar. The eggs hatched to maggots, then young flies. Unable to reach the meat, flies laid their eggs on the gauze of the second jar and the maggots hatched on the gauze, not on the meat. No eggs were laid on the paper or the meat of the third jar, so it remained free of maggots. With this repeatable experiment, Redi proved scientifically that life, the maggots, comes from life, the flies, and not from non life, the dead meat.

5. Redi filled six jars with decaying meat. Conditions Results
Chapter 1
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?

6. So now there are two hypotheses:
Chapter 1
History of Microbiology
So now there are 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.

7. Nutrient broth placed in flask, heated, not sealed Microbial growth
Chapter 1 The Microbial World and You
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?

8. Chapter 1 The Microbial World and You
History of Microbiology
Next experiment, Pasteur’s S-shaped flask kept microbes out but let air in. These experiments form the basis of aseptic technique

9. The Golden Age of Microbiology 1857-1914
Chapter 1 The Microbial World and You
History of Microbiology
The Golden Age of Microbiology
Beginning with Pasteur’s work, discoveries included the relationship between microbes and disease, immunity, and antimicrobial drugs

10. Pasteur showed that microbes are responsible for fermentation.
Chapter 1 The Microbial World and You
History of Microbiology
Pasteur showed that microbes are responsible for fermentation.
Fermentation is the conversation of sugar to alcohol to make beer and wine.
Microbial growth is also responsible for spoilage of food.
Bacteria that use alcohol and produce acetic acid spoil wine by turning it to vinegar (acetic acid).

11. Chapter 1 The Microbial World and You
History of Microbiology
Pasteur demonstrated that these spoilage bacteria could be killed by heat that was not hot enough to evaporate the alcohol in wine. This application of a high heat for a short time is called pasteurization.