Faecalibacterium is a genus of obligate anaerobic, Gram-positive bacteria in the family Ruminococcaceae (phylum Firmicutes). It is the most abundant genus in the healthy human colon (5–15% of fecal bacteria) and its depletion is the single most reproducible microbiome finding across disease states. The genus contains multiple species, but faecalibacterium prausnitzii dominates in adults.
For the detailed species page with metal dependencies, arsenic protection data, and disease-specific depletion patterns, see faecalibacterium prausnitzii.
Species
- F. prausnitzii — The dominant species; premier butyrate producer; directly protective against arsenic toxicity [1].
- F. hominis — Recently characterized; produces indole derivatives that activate AhR signaling, with therapeutic implications for ASD [2].
- F. duncaniae — Newly described species from healthy gut.
Why Faecalibacterium Depletion Matters
Faecalibacterium depletion triggers a cascade:
- Lost butyrate → colonocyte energy crisis → barrier failure → endotoxemia.
- Lost HDAC inhibition → reduced Treg differentiation → immune dysregulation.
- Lost oxygen consumption → luminal oxygenation → facultative anaerobe (Enterobacteriaceae) bloom.
- Lost competitive exclusion → pathobiont expansion.
This single genus's loss explains why the same Enterobacteriaceae bloom, barrier failure, and systemic inflammation appear across such diverse conditions.
Metal Connection
Butyrate production depends on iron-sulfur cluster enzymes (butyryl-CoA dehydrogenase). Metal-driven disruption of iron homeostasis can impair Faecalibacterium function even without directly killing it — a subtle but critical mechanism [3] [4].
Cross-References
- faecalibacterium prausnitzii — species page with full detail
- butyrate — primary metabolic output
- short chain fatty acids — broader SCFA context
- iron — iron-sulfur cluster dependency
- dysbiosis — Faecalibacterium depletion as universal dysbiosis marker
- arsenic — direct arsenic protection