Microbiology

• Brief Review• Spontaneous

Generation and Biogenesis

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.

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

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.

History of Microbiology

Ancestors of bacteria were the first life on Earth.

Discovery of Microorganisms

• Antony van Leeuwenhoek (1632-1723)– First person to

observe and describe micro-organisms accurately

– Teeth scrapings, pond water

Figure 1.1b

Van Leeuwenhoek 1684

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)

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

History of Microbiology

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?

Redi filled six jars with decaying meat.

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”

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

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?

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