Odoribacter splanchnicus is a Gram-negative, obligate anaerobic bacterium belonging to the family Odoribacteraceae within the phylum Bacteroidetes. It is a commensal resident of the human colon recognized primarily as a producer of short chain fatty acids, particularly butyrate and propionate, with emerging but complex associations across multiple disease states.
SCFA Production and Gut Health
- O. splanchnicus ferments complex carbohydrates to produce butyrate, propionate, and succinate.
- Butyrate production supports colonocyte energy metabolism and gut barrier integrity.
- Propionate production contributes to gluconeogenesis regulation and appetite signaling.
- As a member of the Bacteroidetes, it occupies a distinct metabolic niche from Firmicutes-derived SCFA producers like faecalibacterium prausnitzii.
Disease Associations
Cancer vs. Autoimmune Opposing Signatures
Odoribacter is one of six genera identified with true opposite directionality in the systematic meta-analysis of cancer versus autoimmune microbiome signatures: increased in cancer studies and decreased in autoimmune cohorts [islam 2022 opposing microbiome signatures autoimmune cancer]. This positions it as a marker of the divergent immune environments rather than a simple beneficial or harmful taxon.
Cardiovascular Disease
- Mendelian randomization identifies Odoribacter as a risk factor for coronary artery disease (OR=1.206) and myocardial infarction [dai 2024 gut microbiota cvd bidirectional mr].
- This finding is notable because it suggests that not all SCFA producers are cardioprotective, and that the specific metabolic outputs or inflammatory context of Odoribacter may differ from other butyrate producers.
- Depleted in viral myocarditis models alongside other commensal anaerobes [xue 2024 colonic microflora metabolic viral myocarditis cvb3].
Colorectal Cancer
- Found in tissue-associated bacterial communities of rectal carcinoma [thomas 2016 tissue bacteria rectal carcinoma 16s].
- Altered following fecal microbiota transplantation in CRC progression models [yu 2023 fmt inhibits crc progression].
IBD and Extraintestinal Manifestations
- Implicated in extraintestinal manifestations of inflammatory bowel disease through MR analyses, suggesting its metabolic products may have systemic effects beyond the gut lumen [lu 2024 ibd extraintestinal manifestations microbiota mr].
Multiple Sclerosis
- Depleted in MS patients, consistent with the broader autoimmune depletion pattern. Its loss may contribute to reduced SCFA availability in the gut brain axis [yadav 2022 ms gut mycobiome fungal bacterial].
Context-Dependent Effects
The contrasting associations of Odoribacter -- protective in some inflammatory contexts but a risk factor for CVD and enriched in certain cancers -- highlight the context-dependent nature of commensal bacteria. Its effects likely depend on the host immune state, dietary substrate availability, and the surrounding microbial community composition.
Connections
- short chain fatty acids -- produces butyrate, propionate, and succinate
- cardiovascular disease -- MR evidence as CAD risk factor despite SCFA production
- colorectal cancer -- enriched in cancer cohorts per opposing-signature analysis
- inflammatory bowel disease -- depleted in autoimmune conditions
- multiple sclerosis -- depleted in MS, part of the autoimmune depletion pattern
- dysbiosis -- opposite-directionality genus bridging cancer and autoimmune signatures