Spontaneous Generation to the Germ Theory of Disease

[Bernard NebelKeymaster]

The theory of spontaneous generation is the idea that living organisms could spontaneously arise form nonliving.  Described in the following video:

Weird as this belief seems to us today, it was the dominant belief, even among scientists, up until it was finally disproven by experiments conducted by Pasteur described here:

Be sure that students understand the all the steps of reasoning that made the conclusion inescapable.

Germ theory of disease and Koch’s postulates 

By proving spontaneous generation false, the germ theory of disease came to the fore. That is, growth and reproduction of microorganisms within the body was the cause of given diseases. A watertight proof of this were “Koch’s postulates” listed here:

http://science.umd.edu/classroom/bsci424/BSCI223WebSiteFiles/KochsPostulates.htm

By these postulates, important diseases, e.g. pneumonia, were shown to be caused by certain bacteria. The concept of culturing bacteria can be seen here:

For other diseases, however, all the postulates were true leading to the conclusion that microorganisms were involved, but postulate #2 did’t work. Organisms defied being cultured. What was going on? Have students wrestle with this question.

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