Bacteroidetes

Bacteroidetes is a phylum of Gram-negative, non-spore-forming bacteria that encompasses a wide range of genera, including Bacteroides, Prevotella and Porphyromonas. Members are diverse in morphology and metabolism, typically rod-shaped and non-motile, though some lineages exhibit gliding motility. They are found in soil, freshwater, marine environments, and the gastrointestinal tracts of animals, including humans.

Metabolism and ecology: Many Bacteroidetes are anaerobic or facultatively anaerobic and specialize in the breakdown of complex organic matter, particularly polysaccharides. In environments like soil and the animal gut, they secrete a broad arsenal of carbohydrate-active enzymes (glycoside hydrolases) that enable degradation of plant and animal polymers, contributing to nutrient cycling and digestion.

In humans, Bacteroidetes are one of the major bacterial phyla in the gut microbiota, frequently among the most abundant along with Firmicutes. Bacteroides thetaiotaomicron and Bacteroides fragilis are common commensals that participate in carbohydrate metabolism and immune system interactions. Some members can be opportunistic pathogens, such as Bacteroides fragilis in intra-abdominal infections, and Porphyromonas gingivalis and Prevotella species in periodontal disease.

Classification and genetics: The phylum is divided into several classes, including Bacteroidia, Flavobacteriia, Cytophagia, and Sphingobacteriia. They are genetically diverse and have large genomes with numerous genes encoding carbohydrate-active enzymes. Taxonomy within the group has evolved, with some sources using the name Bacteroidetes or Bacteroidota.

Impact and applications: Ongoing research investigates their roles in health and disease, their ecological functions in biogeochemical cycles, and potential uses in biotechnology, such as enzyme discovery for lignocellulose degradation.