Chapter: Essential Microbiology: Procaryote Diversity

 Phylum Bacteroidetes

No unifying phenotypic feature characterises this diverse group, but their phylogenetic closeness causes them to be placed together. In light of this, we can only consider ex-amples, without claiming them to be in any way representative.

The genus Flavobacterium takes its name from the yellow carotenoid pigments se-creted by its members. These are aerobic, free-living, aquatic forms, although they are also associated with food spoilage.

In contrast, Bacteroides species are obligate anaerobes found in the human gut, where they ferment undigested food to acetate or lactate. Here they outnumber all other microbial forms, and are responsible for a significant percentage of the weight of human faeces. Some species can also be pathogenic, and may cause peritonitis in cases where the large intestine or appendix has become perforated.

Representative genera: Bacteroides, Flavobacterium