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 established roles in bile acid deconjugation, increased gut permeability, and promotion of atherosclerosis. Notably, Collinsella is one of the few genera enriched by heavy metal exposure across multiple metals.
Mechanisms of Pathogenicity
Bile Acid Deconjugation
- C. aerofaciens possesses potent bile salt hydrolase (BSH) activity, deconjugating primary bile acids.
- Altered bile acid profiles disrupt FXR signaling in the liver and intestine, reducing cholesterol excretion and promoting lipid accumulation.
- Deconjugated bile acids are more readily converted to secondary bile acids (DCA, LCA) by other bacteria, compounds that are pro-inflammatory and potentially genotoxic in the colon.
Gut Barrier Disruption
- Collinsella increases intestinal permeability by downregulating tight junction proteins in colonocytes.
- Promotes a "leaky gut" state that enables LPS translocation and systemic inflammation -- a direct pathway to atherosclerosis.
- Produces hydrogen and CO2 gas, contributing to bloating and GI discomfort.
Lipid and Cholesterol Metabolism
- Alters host cholesterol metabolism by reducing hepatic bile acid synthesis via disrupted FXR signaling.
- Associated with increased serum LDL-cholesterol and triglycerides.
- Reduces cholesterol excretion via altered bile acid cycling, contributing to hyperlipidemia.
Disease Associations
- Cardiovascular disease/atherosclerosis: one of the most consistently enriched taxa in CVD. Linked to arterial stiffness and carotid intima-media thickness [li 2021 network gut microbiome biomarkers carotid atherosclerosis]. Part of the pro-atherogenic microbiome signature [zhu 2023 gut microbiota metabolic pathways cvd].
- Rheumatoid arthritis: enriched in RA patients; C. aerofaciens promotes Th17 polarization and increases gut permeability, potentially enabling molecular mimicry and autoimmune activation.
- Type 2 diabetes: enriched in T2D; associated with insulin resistance and altered glucose metabolism.
- Autism spectrum disorder: enriched in ASD children alongside lactobacillus and Corynebacterium; associated with altered bile acid metabolism [strati 2017 altered gut microbiota mycobiota asd].
- Symptomatic atherosclerosis: enriched in patients with symptomatic vs asymptomatic carotid plaques.
Heavy Metal Enrichment
- Collinsella is a shared pathobiont across multiple metal exposures -- enriched by arsenic, lead, and mercury in human studies [rezazadegan 2025 heavy metals gut microbiota systematic review].
- This cross-metal enrichment pattern is unusual and suggests that Collinsella possesses inherent metal tolerance mechanisms or benefits from the ecological vacuum created when metal-sensitive commensals are depleted.
- Metal-driven Collinsella expansion may represent a direct mechanistic link between environmental metal exposure and cardiovascular disease via bile acid dysregulation and barrier disruption.
- Depleted by Mediterranean diet interventions, which also reduce heavy metal bioavailability through chelation by polyphenols and fiber.
Key Metabolites
- Deconjugated bile acids -- BSH-mediated deconjugation alters enterohepatic circulation.
- Hydrogen and CO2 -- gas production from carbohydrate fermentation.
- Lactate -- minor fermentation product.
Connections
- cardiovascular disease -- enriched in CVD; promotes atherosclerosis via bile acids and barrier disruption
- rheumatoid arthritis -- enriched; Th17 polarization and gut permeability
- type 2 diabetes -- enriched; linked to insulin resistance
- autism spectrum disorder -- enriched in ASD children
- arsenic -- enriched by arsenic exposure
- lead -- enriched by lead exposure
- mercury -- enriched by mercury exposure
- iron -- indirectly relevant; may benefit from iron-driven depletion of competitors
- dysbiosis -- its enrichment signals pro-inflammatory dysbiosis
- inflammation -- increases gut permeability and LPS translocation
- gut metal microbiome -- metal-tolerant pathobiont; cross-metal enrichment pattern
- oxidative stress -- altered bile acid metabolism promotes oxidative damage
- blautia -- opposing trends; Blautia depleted where Collinsella enriched in CVD