Human commensal bacterium

Human commensal bacteria comprise the diverse, predominantly non-pathogenic bacterial species that naturally inhabit various surfaces and cavities of the human body, including the gastrointestinal tract, skin, mouth, and vagina. Together, they perform essential biological functions such as modulation of the immune system, prevention of colonization by pathogens, digestion of complex carbohydrates (with production of beneficial metabolites like short chain fatty acids), vitamin synthesis, and maintenance of mucosal integrity. Disturbances in their balance (dysbiosis) have been implicated in diseases ranging from infections to chronic inflammatory conditions and metabolic syndromes. They are not a molecular target or receptor, but rather a population of organisms with broad relevance to human physiology and health, as well as to the therapeutic effects and side effects of microbiome-modifying interventions ([1](https://en.wikipedia.org/wiki/Human_microbiome), [2](https://pmc.ncbi.nlm.nih.gov/articles/PMC5426469/), [3](https://pmc.ncbi.nlm.nih.gov/articles/PMC6554327/), [4](https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1244293/full), [5](https://www.gutmicrobiotaforhealth.com/glossary/commensal-bacteria/)).

Other names

Human microbiotahuman gut floranormal floracommensal bacteria

Competitive inhibition of pathogen colonization (nutrient and site competition) Production of antimicrobial peptides and metabolites (e.g., SCFAs lower pH, inhibit growth) Modulation of host immune signaling pathways Enzymatic breakdown of dietary components inaccessible to the host