Bacteroides thetaiotaomicron
Bacteria › Pseudomonadati › Bacteroidota › Bacteroidia › Bacteroidales › Bacteroidaceae › Bacteroides › Bacteroides thetaiotaomicron
Synonyms: Bacillus thetaiotaomicron; Bacteroides fragilis subsp. thetaiotaomicron; Pseudobacterium thetaiotaomicron; Sphaerocillus thetaiotaomicron
Biology & Ecology
Biology
Gram Statusgram-negative
Oxygen Toleranceobligate anaerobe
Morphologybacillus (rod)
Key Traits
- mucin-degrading
Ecology
Primary Nichesgut
Reservoirhuman
Clinical Profile
Pathobiont
yes
no
context dependent
unknown
Clinical Rolescommensal
Typical Specimenstool
Clinical Associations:
E2
E3 — Strong human clinical evidence
E2 — Moderate human evidence
E1 — Limited / preliminary
GF C57BL/6 mice monocolonized with B. thetaiotaomicron (n=6–10) showed no detectable translocation to mesenteric veins, MLNs, or liver (CFU=0 at all extra-intestinal sites), no gut barrier leakage, and no induction of anti-RNA IgG or anti-dsDNA IgG autoantibodies at 8 weeks post-colonization; Th17 cells were not expanded in small intestinal lamina propria or MLNs (n=5 per group), in contrast to E. gallinarum monocolonization.
PMID:
29590047
D018988
Bacterial Translocation
D000069196
Gastrointestinal Microbiome
E2
E3 — Strong human clinical evidence
E2 — Moderate human evidence
E1 — Limited / preliminary
B. thetaiotaomicron lysate or RNA co-cultured with murine and human hepatocytes did not significantly induce ERV gp70, β2-glycoprotein I, type I IFN-α, or AhR/CYP1A1 expression above medium control (n=3 each); serum anti-B. thetaiotaomicron RNA IgG was not elevated in SLE (n=15) or AIH (n=17) patients versus healthy controls (n=9), confirming immunological quiescence relative to E. gallinarum.
PMID:
29590047
E2
E3 — Strong human clinical evidence
E2 — Moderate human evidence
E1 — Limited / preliminary
Intramuscular vaccination against B. thetaiotaomicron in autoimmune-prone (NZW×BXSB)F1 mice had no effect on serum autoantibody levels or survival, confirming that B. thetaiotaomicron does not drive autoimmune pathology and that the autoimmune response is specific to E. gallinarum.
PMID:
29590047
E2
E3 — Strong human clinical evidence
E2 — Moderate human evidence
E1 — Limited / preliminary
Bacteroides thetaiotaomicron was significantly enriched in anti-PD-1 non-responders versus responders by metagenomic WGS in fecal samples from 25 metastatic melanoma patients (14R, 11NR), identifying it as part of a gut microbiome signature associated with immunotherapy non-response (Fig. 2F).
PMID:
29097493
Last reviewed: 2026-04-03
Evidence Timeline
Related Taxa
Shared Niche = same body site
Shared Risk = same vulnerable population
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