Bacteroidota

Bacteroidota is a phylum of bacteria within the domain Bacteria. Members are widespread in soil, freshwater, and marine environments and form a major component of many animal-associated microbiomes, notably the mammalian gut. The name Bacteroidota reflects recent taxonomic standardization; in some classifications the group has been referred to as Bacteroidetes, with Bacteroidota as an updated or synonymous designation.

Taxonomically, Bacteroidota encompasses several classes, including Bacteroidia, Flavobacteriia, Cytophagia, and Sphingobacteriia, which together give rise to orders such as Bacteroidales, Flavobacteriales, Cytophagales, and Sphingobacteriales. Families within the phylum include Bacteroidaceae, Prevotellaceae, and Flavobacteriaceae, among others. Members are phylogenetically diverse but commonly share Gram-negative cell envelopes.

Physiologically, Bacteroidota are mostly chemoorganotrophs that utilize organic carbon sources. Many are anaerobic and adapted to nutrient-rich habitats, such as the gut or sediment; however, some members are aerobic. They are known for degrading complex polysaccharides and plant-derived polymers, contributing to carbon cycling in ecosystems and to the digestive capabilities of their hosts.

In humans, Bacteroidota are a dominant phylum in the gut microbiota, with genera such as Bacteroides and Prevotella playing key roles in fermenting dietary fiber and producing short-chain fatty acids. While many are benign or beneficial, some species are opportunistic pathogens. The phylum remains a focal point of studies on microbiome structure, metabolism, and host interactions.