Louis Pasteur Discovers Anaerobiosis

An anaerobic organism or anaerobe is any organism that does not require oxygen for growth, could possibly react negatively and may even die in its presence.

There are three types: obligate anaerobes, which cannot use oxygen for growth and are even harmed by it; aerotolerant organisms, which cannot use oxygen for growth, but tolerate the presence of it; and facultative anaerobes, which can grow without oxygen but can utilize oxygen if it is present.

Long before the mechanism of fermentation was understood, Pasteur discovered an important regulatory phenomenon of carbohydrate metabolism. He observed that yeast consumes more sugar anaerobically than aerobically. This so-called Pasteur effect has been subject of many controversies and an analysis of the development of the concepts has been presented. Among the key errors made in the early evaluations was to emphasize the control of end product formation rather than of hexose utilization. The Pasteur phenomenon as understood at present is a complex coordinated control mechanism which operates at several levels.

Pasteur Effect: (noun) - the inhibiting effect of oxygen upon a fermentative process (as one carried on by facultative anaerobic organisms)