Bacteroides Caccae

Overview

Bacteroides caccae is a Gram-negative, obligate anaerobic member of the bacteroidetes phylum and a common fiber-degrading commensal in the human colon. While less individually prominent than bacteroides fragilis or bacteroides thetaiotaomicron, B. caccae has emerged as a significant organism in the developmental metal vulnerability framework — it is the most reproducible lead-depleted taxon across multiple study populations, suggesting particular sensitivity to heavy metal disruption during critical developmental windows.

Metal Dependencies

Like other Bacteroides, B. caccae requires iron for various metabolic processes including fumarate reductase and cytochrome-dependent electron transport. Its obligate anaerobic lifestyle makes it sensitive to iron-mediated oxidative stress (Fenton chemistry), which may partly explain its vulnerability to lead exposure — lead disrupts iron homeostasis and generates reactive oxygen species.

Key Enzymes and Functional Features

  • Polysaccharide utilization loci (PULs) — B. caccae encodes multiple PUL systems for degrading complex dietary fibers including plant cell wall polysaccharides, pectins, and hemicelluloses
  • Beta-glucosidase — Contributes to the breakdown of dietary glycosides and plant polyphenol metabolism
  • Bile salt hydrolase — Participates in bile acid deconjugation, contributing to the broader Bacteroides role in bile acid metabolism and fxr signaling

Ecological Role

In the healthy gut, B. caccae contributes to the primary degradation of dietary fiber, releasing oligosaccharides and simple sugars that cross-feed butyrate-producing Firmicutes. Its loss through metal-induced depletion therefore has cascading effects on the broader community's SCFA output — a mechanism by which prenatal metal exposure can produce functional consequences that persist years beyond the original exposure.

Lead Sensitivity — The Defining Feature

The PROGRESS cohort study (prospective, n=123, Mexico City) demonstrated that prenatal lead exposure in both the 2nd and 3rd trimesters was consistently associated with depletion of B. caccae in the childhood gut microbiome at ages 9-11 years eggers 2023 prenatal lead exposure gut microbiome childhood. Key findings:

  • B. caccae exceeded the weighted quantile sum (WQS) importance threshold in ≥80% of repeated holdouts for both trimesters, making it one of the most reproducibly Pb-depleted taxa
  • This depletion persisted years after the prenatal exposure window, consistent with developmental programming of the gut microbiome
  • Co-depleted taxa included bifidobacterium longum, Bifidobacterium bifidum, Ruminococcus gnavus, and Alistipes indistinctus — suggesting a lead-sensitive microbial consortium

The consistency of B. caccae depletion with lead exposure across studies from different populations represents one of the most reproducible findings in the metals-microbiome field eggers 2023 prenatal lead childhood gut microbiome progress.

Conditions Associated

Currently no disease-specific enrichment patterns. The primary association is depletion under lead exposure, with implications for downstream SCFA production and fiber metabolism in metal-exposed populations.

Cross-References

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