Human intestinal microbiota

The **human intestinal microbiota** refers to the diverse community of microorganisms—including bacteria, archaea, fungi, and viruses—that reside within the human gastrointestinal (GI) tract, primarily the large intestine[1][2][3][5]. This ecosystem contributes key functions to host physiology, including fermentation of otherwise indigestible dietary components, synthesis of vitamins, protection against pathogenic microbes, shaping of the immune system, energy harvest, and maintenance of intestinal barrier integrity[1][2][3]. The microbiota is predominantly composed of bacteria from the phyla Firmicutes, Bacteroidetes, Actinobacteria, and Proteobacteria, comprising hundreds of distinct species, with proportions varying between individuals and across life stages or disease states[1][2][3][5]. Dysbiosis, or imbalance in the microbial community, has been implicated in a range of diseases—including inflammatory, metabolic, autoimmune, and infectious conditions—prompting research and therapeutic interest in approaches such as probiotics, prebiotics, antibiotics, and fecal microbiota transplantation[1][2][3]. Importantly, the human intestinal microbiota is a **complex biological community** rather than a single molecular entity or canonical drug target, so it does not fit traditional definitions of receptor, enzyme, transporter, etc., but instead is a dynamic multicellular ecosystem with wide-ranging systemic effects[1][2][3].

Other names

Human gut microbiotaHuman gut floraHuman intestinal floraHuman intestinal microbiomeGut microbiome

Modulation of microbial composition and diversity. Restoration of eubiosis (microbial balance) or disruption (dysbiosis). Alteration of short-chain fatty acid production. Regulation of host immune responses. Enhancement of colonization resistance to pathogens.