Some 180 species of Bacteroidetes bacteria are non-sporeforming, Gram-negative, anaerobic rods usually found in soil and sediments. Some species have flagella for motility. Bacteroidetes are known to have a remarkable ability to digest and grow on a variety of complex substrates including cellulose, chitin, and agar.Of the three large groups that compose the phylum, the family Bacteroidaceae typically is found in the intestinal tracts and mucous membranes of warm-blooded animals, including humans.
Some species can cause or exacerbate abscesses and other infections in humans if they gain access and tissues. In the gastrointestinal tract, however, most species have a symbiotic relationship and make up about 30% of the intestinal microbiota. The bacteria help break down food and produce valuable nutrients and energy.
Bacteroidetes found in soil are typically decomposers which contribute to the turnover of polymeric carbon.