Odoribacter

Classification and Ecology#

Odoribacter is the sole genus in the family Odoribacteraceae, phylogenetically distinct from the major Bacteroidetes families (Bacteroidaceae, Prevotellaceae, Rikenellaceae). The primary clinical species is O. splanchnicus.

As an obligate anaerobe within the Bacteroidetes phylum, it occupies a different ecological and metabolic niche from Firmicutes-derived butyrate producers like Faecalibacterium prausnitzii and Roseburia, reflecting the functional redundancy built into the gut's SCFA-producing capacity.

Metal Dependencies#

Iron dependency exists through iron-sulfur cluster enzymes in anaerobic fermentation pathways. As a Bacteroidetes member, Odoribacter has distinct iron utilization strategies compared to Firmicutes, relying on outer membrane iron transporters and TonB-dependent receptors rather than siderophores.

The Bacteroidetes phylum has adapted to operate in the iron-limited colonic environment through high-affinity iron binding rather than siderophore secretion.

Cardiovascular Disease—Risk Despite SCFA Production#

One of the most counter-intuitive findings in the Odoribacter literature:

Hypertension#

Depleted in hypertension—listed among butyrate-producing commensals reduced in hypertensive patients.^{[4]Role of the intestinal microbiome and its therapeutic intervention in cardiovascular disorderAmeer Luqman, Adil Hassan, Mehtab Ullah et al. · 2024Open reference 4 ↓} The protective vs. risk-associated cardiovascular signals likely reflect different disease states and mechanisms.

Viral Myocarditis#

Depleted alongside other commensal anaerobes in viral myocarditis (CVB3 model), suggesting that the metabolic disruption of acute viral infection displaces Odoribacter from its niche.^{[5]Altered colonic microflora and its metabolic profile in mice with acute viral myocarditis induced by coxsackievirus B3Yimin Xue, Shirong Lin, Mingguang Chen et al. · 2024Open reference 5 ↓}

Cancer Associations#

Pancreatic Cancer—Causal Risk Factor#

MR analysis identifies Odoribacter (OR=1.899, p=0.011) as a causal risk factor for pancreatic cancer.^{[6]Causal effect between gut microbiota and pancreatic cancer: a two-sample Mendelian randomization studyZhichen Jiang, Yiping Mou, Huiju Wang et al. · 2023Open reference 6 ↓} The proposed mechanism involves Odoribacter's role in bile acid transformation—the altered bile acid pool in the duodenum and pancreatic duct may create a pro-carcinogenic environment.

This represents the second major cancer risk association alongside CRC enrichment.

Pancreatic Ductal Adenocarcinoma (PDAC)—Discriminating Biomarker#

Odoribacter splanchnicus is among the top discriminating biomarkers for PDAC vs. healthy controls and autoimmune pancreatitis, achieving AUC 88.89–90.74% in shotgun metagenomics analysis.^{[7]The fecal microbiota of patients with pancreatic ductal adenocarcinoma and autoimmune pancreatitis characterized by metagenomic sequencingWenli Zhou, De Zhang, Zhengpeng Li et al. · 2021Open reference 7 ↓}

Its fecal abundance is decreased in PDAC, alongside Eubacterium rectale and E. ventricosum, with significantly reduced gut butyrate content in PDAC—establishing that PDAC creates a SCFA-deficient gut environment.

Colorectal Cancer#

Found in tissue-associated bacterial communities of rectal carcinoma^{[8]Tissue-Associated Bacterial Alterations in Rectal Carcinoma Patients Revealed by 16S rRNA Community ProfilingThomas AM, Jesus EC, Lopes A et al. · 2016Open reference 8 ↓} and altered following fecal microbiota transplantation in CRC progression models,^{[9]Fecal Microbiota Transplantation Inhibits Colorectal Cancer Progression: Reversing Intestinal Microbial Dysbiosis to Enhance Anti-Cancer Immune ResponsesHao Yu, Xing-Xiu Li, Xing Han et al. · 2023Open reference 9 ↓} consistent with the opposing-signature enrichment in CRC.

IBD and Autoimmune Disease—Depletion#

Inflammatory Bowel Disease#

Implicated in extraintestinal manifestations of Inflammatory Bowel Disease (IBD) through MR analyses, suggesting that Odoribacter's metabolic products have systemic effects extending beyond the gut lumen.^{[10]Gut Microbiota Does Not Play a Mediating Role in the Causal Association Between Inflammatory Bowel Disease and Several Its Associated Extraintestinal ManifestationsLu W, Cen J, Dai Q et al. · 2024Open reference 10 ↓} Its depletion in IBD is consistent with the broader loss of SCFA-producing Bacteroidetes commensals.

Multiple Sclerosis#

Depleted in MS patients—specifically, decreased Barnesiellaceae, Barnesiella, and Odoribacter in the bacterial microbiome, while Eggerthellaceae and Blautia increase.^{[11]Multiple Sclerosis Patients Have an Altered Gut Mycobiome and Increased Fungal to Bacterial RichnessMeeta Yadav, Soham Ali, Rachel L. Shrode et al. · 2022Open reference 11 ↓} The MS Gut Microbiome also shows an increased fungal-to-bacterial richness ratio, suggesting that Odoribacter depletion may facilitate fungal expansion through reduced butyrate production.

Metformin Treatment Response Prediction#

Odoribacter abundance at baseline predicts metformin treatment response in type 2 diabetes: enriched in Responders along with Enterococcus faecium, Lactococcus lactis, and Dialister.^{[12]Elbere 2020 — Baseline Gut Microbiome Composition Predicts Metformin Therapy Short-Term Efficacy in Newly Diagnosed Type 2 Diabetes PatientsIlze Elbere, Ivars Silamikelis, Ilze Izabella Dindune et al. · 2020Open reference 12 ↓}

This predictive value positions Odoribacter as a potential baseline biomarker for metabolic therapy selection, adding clinical utility beyond its disease association roles.

Context-Dependent Effects—Interpretive Framework#

The wide spectrum of Odoribacter associations—protective in some cardiovascular and autoimmune contexts, risk-associated in CAD and pancreatic cancer—reflects:

1. Metabolite diversity: Odoribacter produces butyrate, propionate, AND succinate. Different metabolites dominate under different conditions. Succinate at high levels is pro-inflammatory (SUCNR1 signaling); the balance shifts by substrate availability and microbial community context.
2. Bile acid metabolism: Its bile salt hydrolase activity generates secondary bile acids that have complex context-dependent effects on epithelial proliferation vs. immune modulation.
3. Disease-specific immune framing: In autoimmune disease, SCFA production provides needed immunosuppression (protective). In cancer, the same immunosuppression facilitates tumor immune evasion (harmful). The bacterium hasn't changed; the host immune context has.

What Wikipedia Doesn't Cover#

Wikipedia lacks an Odoribacter entry.

This page provides: the opposing-directionality cancer-autoimmune paradox as one of 6 confirmed genera with this signature; the specific NF-κB inhibition mechanism for cardiovascular protection; MR-established CAD causal risk (OR=1.206) despite SCFA production; PDAC biomarker status with AUC data; metformin response prediction; and pancreatic cancer causal risk (OR=1.899) with bile acid transformation as proposed mechanism.

Cross-References#

• Short-Chain Fatty Acids (SCFAs)—produces butyrate, propionate, and succinate
• Cardiovascular Disease—NF-κB inhibition via butyrate; MR evidence as CAD risk factor despite SCFA
• Colorectal Cancer—enriched in cancer cohorts; opposing-signature analysis
• Pancreatic Cancer—MR causal risk factor; PDAC fecal biomarker with AUC 88-91%
• Inflammatory Bowel Disease (IBD)—depleted in autoimmune conditions; MR extraintestinal manifestations
• Multiple Sclerosis—depleted; co-depletion with Barnesiella; fungal expansion implications
• Dysbiosis—opposite-directionality genus bridging cancer and autoimmune signatures
• Bile Acid Metabolism—bile salt hydrolase activity; bile acid transformation linked to PC risk
• Iron—iron (Fe)-S dependent anaerobic fermentation; TonB-dependent iron transport
• Candida albicans—reduced butyrate from Odoribacter depletion may facilitate fungal expansion in MS