Bacteroidetes

The phylum Bacteroidetes is composed of three large classes of bacteria that are widely distributed in the environment, including in soil, in sediments, sea water and in the guts of animals.

By far, the Bacteroidales class are the most well-studied, including the genus Bacteroides (an abundant organism in the feces of warm-blooded animals including humans), and Porphyromonas, a group of organisms inhabiting the human oral cavity.

Members of the genus Bacteroides are opportunistic pathogens. Rarely are members of the other two classes pathogenic to humans.

Researcher Jeffrey Gordon and his colleagues found that obese humans and mice had intestinal flora (gut flora) with a lower percentage of a family of bacteria called Bacteroidetes and more Firmicutes. However, they are unsure if Bacteroidetes prevent obesity or if these intestinal flora are merely preferentially selected by intestinal conditions in those who are not obese.