The friendly anaerobes

Anaerobic bacteria include the most pathogenic of microorganisms. Their primary function, however, is hardly to cause illness. They rarely are involved in epidemics or in clinically significant infections. Some organisms, e.g. lactobacilli, control the normal vaginal ecosystem, and the intestinal anaerobes probably are instrumental in restraining the growth of Clostridium difficile in human carriers. The main role of anaerobes appears to be the provision of catabolic enzymes for organic compounds that cannot be digested by enzymes of eukaryotic origin. They are needed for the catabolism of cholesterol, bile acids, and steroid hormones; they hydrolyze a number of flavonoid glycosides to anticarcinogens; and they detoxify certain carcinogens. Anaerobic enzymes are used industrially in the production of cheese; the conversion of starch to sweeteners; and the transformation of sawdust, wood chips, and waste paper to fuel. Indeed, the anaerobes may well be the gene bank on which future generations of eukaryotic organisms will rely to adapt successfully to an ever-changing world.