Prevotellaceae

A family of Gram-negative, obligate anaerobic bacteria within the phylum Bacteroidota (formerly Bacteroidetes) that includes the genus prevotella and the recently described alloprevotella. Prevotellaceae are specialist fiber fermenters producing short-chain fatty acids, yet their relationship with human disease is strikingly paradoxical: they are the most consistently depleted family in Parkinson's disease but a causal risk factor for autism spectrum disorder via Mendelian randomization. This duality makes Prevotellaceae one of the most instructive examples of context-dependent host-microbe interactions in the gut.

Taxonomy

  • Family Prevotellaceae, order Bacteroidales, class Bacteroidia, phylum Bacteroidota.
  • Key genera: prevotella (including P. copri, P. melaninogenica), alloprevotella, Paraprevotella, Hallella.
  • Prevotella copri is the dominant species in non-Western, fiber-rich diets and is a primary driver of the "Prevotella enterotype."

Metal Dependencies

Iron:

  • Iron-dependent succinate dehydrogenase participates in the fumarate respiration pathway, a key anaerobic energy-generating strategy in Bacteroidales.
  • Prevotellaceae encode iron uptake systems including TonB-dependent receptors for iron-siderophore complexes, though they are generally less aggressive iron competitors than Enterobacteriaceae.
  • In iron-depleted environments (host nutritional immunity), Prevotellaceae may lose competitive advantage to siderophore-producing pathobionts, contributing to their depletion in inflammatory conditions.

Key Enzymes and Metabolic Features

  • Glycoside hydrolases: Prevotellaceae encode extensive polysaccharide utilization loci (PUL) for degrading plant-derived complex carbohydrates — xylan, arabinoxylan, pectin. This makes them indicators of fiber-rich diets.
  • Peptidases: Prevotella species also degrade host-derived glycoproteins, including mucin, which can trigger inflammatory responses when Prevotellaceae infiltrate the mucosal layer.
  • Succinate dehydrogenase: Iron-dependent enzyme in fumarate respiration.

Ecological Role

In the Healthy Gut

Prevotellaceae thrive in individuals consuming plant-rich, fiber-heavy diets. They are dominant in non-Western populations and relatively depleted in individuals consuming high-fat, high-protein Western diets. Their SCFA production (primarily succinate and propionate) contributes to:

  • Colonic epithelial energy supply
  • Anti-inflammatory signaling via FFAR2/FFAR3
  • Gut barrier maintenance

The Prevotellaceae Paradox

The family's dual role as both beneficial (SCFA production, fiber fermentation) and potentially harmful (mucosal invasion, T-cell activation) depends on context:

  • Beneficial: In the gut lumen, Prevotellaceae ferment dietary fiber into SCFAs and maintain community diversity
  • Harmful: When Prevotellaceae infiltrate the mucosal layer, they can trigger T-cell and antibody responses, promoting inflammation li 2023 gut microbiota asd bidirectional mr

Conditions Associated

Parkinson's Disease (Depleted)

Reduced Prevotellaceae is the most consistent PD microbiome finding across multiple meta-analyses pendergrass 2026 microbial metallomics parkinsons ferroptosis romano 2021 meta analysis gut microbiome parkinsons. Depletion correlates with reduced SCFA production and increased gut permeability, potentially facilitating alpha synuclein propagation from gut to brain via the vagus nerve. Loss of Prevotellaceae alongside lachnospiraceae and faecalibacterium represents the core PD dysbiosis signature.

Autism Spectrum Disorder (Risk Factor)

Prevotellaceae causally increases ASD risk (IVW OR = 1.24, 95% CI: 1.09-1.40, p = 9.2 x 10^-4), surviving FDR correction li 2023 gut microbiota asd bidirectional mr. The mechanism may involve mucosal infiltration by Prevotellaceae, triggering T-cell and antibody responses that exacerbate neuroinflammation via the gut-brain axis.

Schizophrenia (Enriched)

Prevotellaceae is enriched in schizophrenia patients with violent behaviors (OR = 1.11, 95% CI 1.03-1.20, p = 1.4 x 10^-3) by MR, contrasting with its depletion in PD and depression.

Depression (Depleted)

Prevotellaceae show the most pronounced reduction in depressed patients, with decreased richness (p = 0.005), total observed species (p = 0.002), and phylogenetic diversity (p = 0.001).

Key Studies

Open Questions

  1. Why is Prevotellaceae protective in PD but a risk factor in ASD? The opposing directionality across neurological conditions is unexplained. Species-level differences (P. copri vs. P. melaninogenica), mucosal vs. luminal location, and immune context may resolve this paradox.
  2. Does dietary fiber supplementation restore Prevotellaceae in PD patients? Prebiotic intervention targeting Prevotellaceae expansion is an untested therapeutic hypothesis for PD.

Cross-References

  • prevotella — the primary genus; Prevotella copri drives the "Prevotella enterotype"
  • alloprevotella — a recently described genus within the family
  • parkinsons disease — Prevotellaceae depletion is the hallmark PD microbiome signature
  • autism spectrum disorder — Prevotellaceae causally increases ASD risk
  • schizophrenia — enriched in violent behavior phenotype
  • depression — most pronounced family-level reduction in depressed patients
  • lachnospiraceae — co-depleted with Prevotellaceae in PD
  • alpha synuclein — gut permeability from Prevotellaceae loss facilitates alpha-synuclein propagation

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