Bacteroides fragilis

MCA-BAC-000033

TaxID: 817 | BacDive: 1585 | Rank: species

Biology & Ecology

Biology

Gram Statusgram-negative

Oxygen Toleranceobligate anaerobe

Morphologybacillus (rod)

Key Traits

capsule-producing
polysaccharide A (PSA)-producing

Ecology

Primary Nichesgut

Reservoirhuman

Metabolites

No metabolite relationships documented for this taxon.

Clinical Profile

Pathobiont

yes no context dependent unknown

Clinical Rolescommensal; opportunistic pathogen

Typical Specimenstool

Risk Contextsimmunocompromised; post-surgical / post-procedural

Virulence Factors VF1421 Bfp1 · VF1310 BFT · VF1416 BfUbb · VF1418 GA1 T6SS · VF1419 GA2 T6SS · VF1417 GA3 T6SS · VF1423 GA3 T6SS secreted effectors · VF1420 NanH sialidase · VF1415 PSA

Clinical Associations:

Bacteroides fragilis exhibits mucosal/luminal lineage divergence (within-host evolution) in germ-free monocolonised mice but did not translocate to the liver, unlike Enterococcus gallinarum, suggesting that within-host evolutionary diversification is a broad property of gut bacteria but that liver translocation capacity is taxon-specific.

PMID: 35831502

D018988 Bacterial Translocation

Last reviewed: 2026-04-01

Evidence Timeline

2022 animal model

Related Taxa Shared Niche = same body site Shared Risk = same vulnerable population ⓘ