WikiBiomeThe human microbiome encyclopediaRanked matches across titles, topics, categories, and article introductions.
A Gram-negative, obligate anaerobic genus within the family veillonellaceae (class Negativicutes, phylum Firmicutes) defined by its specialized amino acid fermentation -- the genus name literally means "acid from amino acids." Acidaminococcus ferments glutamate as its p…
The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that functions as a master sensor at the intersection of gut microbial metabolism, environmental chemical exposure, and immune regulation. It is expressed broadly across immune cells, intesti…
A Gram-negative, obligate anaerobic, mucin-degrading bacterium that colonizes the intestinal mucus layer and has emerged as one of the most important next-generation probiotics. A. muciniphila is consistently depleted in disease states associated with metal dyshomeostas…
A Gram-negative, obligate anaerobic genus within the Bacteroidetes phylum (family Rikenellaceae). Alistipes occupies a complex and context-dependent role in the gut ecosystem — some species carry well-documented anti-inflammatory properties, while the genus is paradoxic…
Alloprevotella is a genus of Gram-negative, obligate anaerobic bacteria within the family Prevotellaceae that represents a distinct clade from prevotella with specific protective roles in type 2 diabetes prevention and metabolic health. Alloprevotella depletion is one o…
Anaerococcus is a genus of Gram-positive, obligate anaerobic cocci within the phylum Firmicutes. It is a normal inhabitant of the human vaginal, skin, and gastrointestinal microbiota, but is recognized as an opportunistic pathogen in dysbiotic states, particularly when …
A genus of Gram-positive obligate anaerobes in the family Lachnospiraceae (Clostridium cluster XIVa) that occupy a critical metabolic relay position in gut ecosystem stability: converting lactate to butyrate. Anaerostipes is one of the most consistently depleted genera …
Anaerotruncus is a Gram-positive obligate anaerobic genus within the Ruminococcaceae (Firmicutes). First isolated from human feces, it is a minor member of the healthy gut community that has attracted attention for its consistent enrichment in aging-related conditions a…
This page serves as a cross-reference point for the existing ahr concept page, which provides comprehensive coverage of AhR signaling, microbiome-derived ligands, and immune regulation. The aryl hydrocarbon receptor is a ligand-activated transcription factor that integr…
A ubiquitous filamentous fungal genus that is both an environmental saprophyte and an opportunistic human pathogen. A. fumigatus is the primary cause of invasive aspergillosis in immunocompromised patients, while A. niger is relevant to food contamination. The genus is …
Atopobium is a genus of obligate anaerobic, Gram-positive bacteria in the phylum Actinobacteria. The primary species of clinical relevance is A. vaginae (recently reclassified as Fannyhessea vaginae), which is one of the hallmark organisms of bacterial vaginosis (BV) an…
Bacteroidaceae is a family of obligate anaerobic, Gram-negative bacteria in the order bacteroidales. The dominant genus is bacteroides, which includes B. fragilis, B. vulgatus, B. thetaiotaomicron, and B. uniformis. Bacteroidaceae are among the most abundant gut bacteri…
Bacteroidales is an order of obligate anaerobic, Gram-negative bacteria within the phylum Bacteroidetes. It includes the families Bacteroidaceae (bacteroides), Prevotellaceae (prevotella), Rikenellaceae, and Porphyromonadaceae (porphyromonas). Bacteroidales are among th…
Bacteroides caccae is a Gram-negative, obligate anaerobic member of the bacteroidetes phylum and a common fiber-degrading commensal in the human colon. While less individually prominent than bacteroides fragilis or bacteroides thetaiotaomicron, B. caccae has emerged as …
A Gram-negative obligate anaerobe and the most clinically significant member of the Bacteroides genus. B. fragilis occupies a unique dual position in gut microbiology: as a non-toxigenic commensal (NTBF), it produces polysaccharide A (PSA) that shapes immune tolerance; …
Bacteroides thetaiotaomicron is one of the most abundant and metabolically versatile commensals of the human gut, routinely cited as a model organism for studying host-microbe symbiosis. Its genome was one of the first human gut bacterial genomes fully sequenced, and su…
A Gram-negative, obligate anaerobic bacterium within the phylum Bacteroidetes and a common member of the healthy human gut microbiota. B. uniformis is a versatile polysaccharide degrader with emerging significance as an anti-inflammatory commensal whose depletion appear…
A Gram-negative obligate anaerobe that exemplifies the commensal-pathobiont spectrum. B. vulgatus is a common component of the healthy gut microbiota, yet is significantly enriched in colorectal cancer and depression, suggesting a context-dependent pathogenic potential.…
Bacteroidetes (recently reclassified as Bacteroidota) is one of the two dominant bacterial phyla in the human gut, together with firmicutes typically comprising 90% of the intestinal microbiota. Bacteroidetes are Gram-negative, obligately anaerobic, non-spore-forming ro…
Barnesiella is a validly published genus of Gram-negative, obligately anaerobic bacteria in the phylum Bacteroidota and family Barnesiellaceae. NCBI Taxonomy assigns the genus NCBITaxon:397864, and LPSN lists Barnesiella Sakamoto et al. 2007 as the correct name ncbi tax…
A genus of Gram-positive, obligate anaerobic bacteria that dominate the infant gut microbiome and remain important commensals throughout life. Bifidobacterium species are distinctive in the metallomics context because some species possess Ni-dependent urease -- an unusu…
Bifidobacterium adolescentis is a Gram-positive, obligate anaerobic species within the phylum Actinobacteria and the dominant Bifidobacterium species in the adult human gut. It is a specialist degrader of resistant starch and dietary fiber, producing acetate and lactate…
Bifidobacterium bifidum is an obligate anaerobic, Gram-positive species that specializes in human milk oligosaccharide (HMO) and mucin glycan degradation. It is one of the earliest colonizers of the infant gut and a widely used probiotic species.
Bifidobacterium breve is a Gram-positive, obligate anaerobic species within the phylum Actinobacteria, predominantly found in the infant gut and breast milk. It is among the earliest colonizers of the neonatal intestine and plays a key role in human milk oligosaccharide…
Bifidobacterium longum is a Gram-positive, obligate anaerobic bacterium and one of the most important commensal species in human health from infancy through old age. Its subspecies — B. longum subsp. longum (adult gut), B. longum subsp. infantis (infant gut, HMO degrade…
Bilophila wadsworthia is a Gram-negative, obligate anaerobic, sulfite-reducing bacterium that has emerged as a key pathobiont linking high-fat diets, taurine metabolism, hydrogen sulfide production, and inflammatory disease. Its unique metabolic niche -- using taurine-c…
A genus of Gram-positive, obligate anaerobic bacteria within the lachnospiraceae family that produces short chain fatty acids and plays a significant role in bile acid metabolism. Key species include B. obeum, B. wexlerae, B. hydrogenotrophica, and B. producta. While pr…
A Gram-negative, obligate anaerobic genus within the Bacteroidetes phylum (family Odoribacteraceae). Despite its relatively recent characterization, Butyricimonas has gained significant attention as a member of the protective butyrate-producing consortium that is consis…
Butyrivibrio is a genus of Gram-positive, obligate anaerobic bacteria within the family Lachnospiraceae (phylum Firmicutes). Originally characterized as a dominant fiber-fermenting genus in the rumen, Butyrivibrio species are also found in the human colon where they con…
The most abundant mineral in the human body, with ~99% stored in bones and teeth. Calcium's biological significance extends far beyond structural support -- it is the universal second messenger in cell signaling, controlling neurotransmitter release, muscle contraction,…
Candida tropicalis is an opportunistic fungal pathogen and occasional gut commensal, increasingly recognized as one of the most clinically significant non-albicans Candida (NAC) species. Once considered a distant runner-up to C. albicans, it has emerged as a major drive…
Caulobacter is a genus of Gram-negative obligate aerobic Alphaproteobacteria, with C. crescentus serving as one of the premier model organisms for studying bacterial cell biology. Found primarily in oligotrophic freshwater environments, Caulobacter is not a gut commensa…
Chlamydia is a genus of obligate intracellular, Gram-negative bacteria with a unique biphasic developmental cycle. The genus includes three species pathogenic to humans: chlamydia trachomatis (STI and trachoma), C. pneumoniae (respiratory infections, atherosclerosis ass…
Chlamydia trachomatis is a Gram-negative, obligate intracellular bacterium and the most common bacterial sexually transmitted infection worldwide. Its biphasic developmental cycle — alternating between the infectious elementary body (EB) and the replicative reticulate b…
A class of Gram-positive, obligate anaerobic bacteria within the phylum Firmicutes that represents the most functionally diverse and clinically significant taxonomic class in the human gut microbiome. Clostridia encompasses the dominant butyrate producers sustaining col…
Clostridioides difficile is the current NCBI name for NCBITaxon:1496 and the correct, medically recommended combination recorded by LPSN. Both records retain Clostridium difficile as a validly published homotypic synonym of the same organism rather than a separate speci…
A large, polyphyletic genus of Gram-positive, obligate anaerobic, spore-forming bacteria encompassing both critical beneficial commensals and dangerous pathogens. Former Clostridium clusters IV and XIVa are now reclassified into ruminococcus-family Ruminococcaceae and l…
Clostridium butyricum is a spore-forming, obligate anaerobic, Gram-positive bacterium and one of the leading next-generation probiotic candidates. The MIYAIRI 588 strain (CBM 588) is approved as a pharmaceutical probiotic in Japan and has expanding clinical evidence acr…
Clostridium symbiosum is a Gram-positive, obligately anaerobic bacterium within the Clostridium cluster XIVa — a taxonomic group enriched for short-chain fatty acid (SCFA) producers and specialized bile acid metabolizers. Despite its ambiguous name (suggesting symbiotic…
A genus of Gram-positive, obligate anaerobic bacteria within the Actinobacteria phylum (family Coriobacteriaceae) that has emerged as a consistent pathobiont enriched in cardiometabolic and autoimmune diseases. C. aerofaciens is the most studied species, with establishe…
An essential trace element with a striking dual nature: required for survival as a cofactor for critical enzymes (SOD1, cytochrome c oxidase, ceruloplasmin), yet toxic in excess through Fenton-like redox cycling and mis metallation of iron-sulfur clusters. Copper is ele…
A Gram-positive, obligate anaerobic genus within the lachnospiraceae family (Firmicutes phylum). Coprococcus is one of the most important butyrate-producing commensals in the human gut and has gained particular attention as the "happiness bug" -- one of very few taxa di…
Dermatitis herpetiformis (DH) is the cutaneous manifestation of celiac disease, presenting as intensely pruritic, grouped vesicles on the elbows, knees, buttocks, and scalp. It is driven by IgA antibodies against epidermal transglutaminase (eTG), the skin homolog of tis…
A genus of Gram-negative, obligate anaerobic, sulfate-reducing bacteria (SRB) that produces hydrogen sulfide (H2S) as its primary metabolic end-product. H2S is a potent cytotoxin that disrupts colonocyte energy metabolism, damages the gut barrier, and promotes chronic i…
Dialister is a genus of Gram-negative, obligate anaerobic bacteria within the family Veillonellaceae that represents one of the strongest protective associations in gut-brain-axis research. Dialister depletion is a consistent and independent biomarker of depression, anx…
This page identifies the contradictions and clinical dilemmas that become visible only when the 236 source pages in this wiki are read together. Each paradox describes a situation where evidence-based dietary or supplementation advice -- advice that is correct for most …
A Gram-positive, obligate anaerobic genus within the lachnospiraceae family (Firmicutes phylum). Dorea occupies a mixed role in the gut ecosystem -- while it is a core member of the healthy human microbiome, several species are consistently enriched in autoimmune and ne…
A Gram-positive obligate anaerobe and key estrobolome member that links metabolic dysbiosis to hormone-driven diseases, particularly endometriosis. E. lenta is remarkable for its ability to inactivate cardiac glycosides (like digoxin) and to produce beta-glucuronidase, …
Erysipelotrichaceae is a family within the phylum Firmicutes that has drawn increasing attention for its consistent enrichment in metabolic disorders. Members of this family are Gram-positive, obligate anaerobes found throughout the mammalian gastrointestinal tract, whe…
A Gram-negative bacterium that spans the commensal-pathogen spectrum, with pathogenic variants (UPEC, STEC, EHEC) deploying nickel-dependent enzymes as virulence factors. E. coli is the model organism for nickel transport biology -- the NikABCDE system was first charact…
A genus of Gram-positive, obligate anaerobic bacteria within the Firmicutes phylum that includes several of the most important butyrate producers in the human colon. Key species are E. rectale, E. hallii (now reclassified as Anaerobutyricum hallii), and E. limosum. Cons…
Faecalibacterium is a genus of obligate anaerobic, Gram-positive bacteria in the family Ruminococcaceae (phylum Firmicutes). It is the most abundant genus in the healthy human colon (5–15% of fecal bacteria) and its depletion is the single most reproducible microbiome f…
The transfer of processed stool from a healthy donor into a recipient's gastrointestinal tract to restore a disrupted microbial community. FMT is the most direct form of microbiome intervention -- replacing the entire community rather than supplementing individual strai…
A Gram-positive obligate anaerobe in the family Ruminococcaceae (Clostridium cluster IV) whose defining metabolic activity is the degradation of dietary flavonoids — the very polyphenols that serve as anti-inflammatory, antioxidant, and antimicrobial agents. When Flavon…
Fusicatenibacter is a Gram-positive obligate anaerobic genus within the Lachnospiraceae (Firmicutes). The primary species, F. saccharivorans, was isolated from human feces and is recognized as a beneficial commensal that produces butyrate and modulates intestinal immune…
An order of Gram-negative, obligate anaerobic bacteria within the phylum Fusobacteriota (formerly Fusobacteria). This order-level page covers the broader taxonomic group that includes the well-characterized genus fusobacterium and its key species fusobacterium nucleatum…
A Gram-negative, obligate anaerobic bacterium that has emerged as the most consistently CRC-associated microorganism in human gut microbiome studies. F. nucleatum is the primary species of concern, originally a commensal of the oral cavity that translocates to colorecta…
A Gram-negative obligate anaerobe that has emerged as a major pathogen in colorectal cancer (CRC) and inflammatory bowel disease. F. nucleatum is significantly enriched in CRC tissue and tumors compared to healthy mucosa, making it one of the strongest microbe-cancer as…
A Gram-negative obligate anaerobe that occupies a paradoxical niche in the gut microbiota: as a weak butyrate producer (short-chain fatty acid), it has anti-inflammatory potential; as a virulent invasive pathobiont in inflammatory bowel disease (particularly ulcerative …
Alphabetical definitions of specialist terms used throughout this wiki. Where a full concept page exists, the term links to it. --- AhR (aryl hydrocarbon receptor) -- A ligand-activated transcription factor that senses microbial metabolites (especially indoles from tryp…
Gordonibacter urolithinfaciens is a Gram-positive, obligate anaerobic bacterium belonging to the family Eggerthellaceae that plays a specialized and critical role in polyphenol metabolism and conversion of ellagic acid to urolithin A. This microbial conversion is one of…
Heavy metals is a widely used but chemically imprecise umbrella term for elements discussed because of their density, persistence, environmental occurrence, or toxicity. One common convention uses density above 5 g/cm3, but density alone does not determine biological ha…
Hungatella hathewayi is a Gram-positive, obligate anaerobic bacterium within the Firmicutes phylum (family Clostridiaceae) that has rapidly emerged as a multi-disease cancer-associated pathobiont. A recently reclassified genus (from Clostridium hathewayi), it is now rec…
Hypoxia refers to a state of low oxygen tension (partial pressure of O₂ < 5% in tissue, vs. ~21% in air). In the context of microbiome metallomics, hypoxia is a critical ecological determinant that reshapes bacterial community structure by favoring obligate and facultat…
Indole is a microbial metabolite produced from tryptophan by bacterial tryptophanase (TnaA). It is one of the most abundant microbial signals in the gut (concentrations reach 250–1,100 µM in the colon) and the primary endogenous ligand for the aryl hydrocarbon receptor …
Microbial tryptophan metabolites produced by gut bacteria through the third branch of tryptophan metabolism -- the indole pathway. Unlike the host-dominated kynurenine pathway (~95% of Trp) and the serotonin pathway (~1-2%), the indole pathway is exclusively microbial a…
Intestinibacter bartlettii is a Gram-positive, obligate anaerobic, spore-forming bacterium within the Firmicutes phylum (Peptostreptococcaceae family). It is a relatively understudied gut commensal that has emerged in Mendelian randomization and metagenomic studies with…
A Gram-positive, obligate anaerobic genus within the Firmicutes phylum (family Oscillospiraceae or Ruminococcaceae depending on classification) that possesses a unique metabolic capability: butyrate production from lysine fermentation rather than from dietary fiber. Thi…
A fundamental ordering of divalent transition metal ion binding affinities, established by Harry Irving and Robert Williams in 1953: Mg2+ < Mn2+ < Fe2+ < Co2+ < Ni2+ < Cu2+ Zn2+ This series holds for virtually all ligands and biological chelators. It means that copper b…
Lachnobacterium is a genus of Gram-positive, obligate anaerobic bacteria within the family Lachnospiraceae (phylum Firmicutes). It is a commensal member of the healthy human gut microbiota, though relatively understudied compared to other Lachnospiraceae genera. Lachnob…
Lachnoclostridium is a genus of obligate anaerobic, Gram-positive bacteria in the lachnospiraceae family. It is a butyrate-producing commensal with emerging clinical significance as a treatment response biomarker and diagnostic marker.
Lachnospira is a genus of Gram-positive, obligate anaerobic bacteria within the lachnospiraceae family (Firmicutes phylum). L. pectinoschiza, the type species, is a specialist pectin fermenter that produces short chain fatty acids from plant-derived polysaccharides. The…
A Gram-negative obligate anaerobe traditionally considered an oral commensal, but increasingly recognized as an opportunistic pathobiont with the ability to translocate from oral biofilms to the gastrointestinal tract and bloodstream. Leptotrichia species are prominentl…
Manganese is an essential trace element with a narrow therapeutic window: required as a cofactor for critical enzymes including Mn-SOD (SOD2), pyruvate carboxylase, arginase, and ribonucleotide reductase, yet profoundly neurotoxic at elevated levels martin 2022 manganes…
A Gram-positive, obligate anaerobic genus within the family lachnospiraceae (phylum Firmicutes) that was recently reclassified from Ruminococcus based on phylogenomic evidence. The key species Mediterraneibacter faecis (formerly Ruminococcus gnavus clade relatives) is a…
Megamonas is a genus of obligate anaerobic, Gram-negative bacteria in the family Veillonellaceae (class Negativicutes, phylum Firmicutes). The type species is Megamonas hypermegale, with M. funiformis also well-characterized. It is a common member of the human gut micro…
Megasphaera is a genus of obligate anaerobic, Gram-negative bacteria in the family Veillonellaceae (class Negativicutes, phylum Firmicutes). The genus occupies two distinct ecological niches — the vaginal microbiome (where it is a hallmark of bacterial vaginosis) and th…
Metal speciation refers to the distribution of a metal among its possible chemical forms — free ions, complexed with organic or inorganic ligands, bound to proteins, or incorporated into mineral phases. In biological systems, speciation determines everything: a metal's …
Methanobrevibacter smithii is the dominant methanogenic archaeon in the human gut, responsible for consuming hydrogen gas produced by fermentative bacteria and converting it to methane. Despite being an archaeon rather than a bacterium, it represents 0–15% of gut microb…
Odoribacter splanchnicus is a Gram-negative, obligate anaerobic bacterium belonging to the family Odoribacteraceae within the phylum Bacteroidota (formerly Bacteroidetes). It is a commensal resident of the human colon recognized primarily as a producer of short chain fa…