Acidaminococcus

A Gram-negative, obligate anaerobic genus within the family veillonellaceae (class Negativicutes, phylum Firmicutes) defined by its specialized amino acid fermentation — the genus name literally means "acid from amino acids." Acidaminococcus ferments glutamate as its primary energy source, a metabolic strategy that links it to protein-rich diets and conditions characterized by altered amino acid metabolism. The genus has emerged as a consistently enriched taxon across breast cancer, schizophrenia, and type 2 diabetes, suggesting a pattern of pathobiont expansion in metabolic and inflammatory diseases.

Taxonomy

  • Acidaminococcus fermentans — the type species; A. massiliensis is a more recently described species relevant to COVID-19 recovery studies.
  • Family Veillonellaceae, order Veillonellales, class Negativicutes, phylum Firmicutes.
  • Like other Negativicutes, Acidaminococcus is Gram-negative despite belonging to the predominantly Gram-positive Firmicutes.

Metal Dependencies

Iron:

  • Iron-sulfur cluster proteins are essential for the glutamate fermentation pathway, particularly in the electron transfer steps of glutaconyl-CoA decarboxylase.
  • Ferredoxin-dependent oxidoreductases support the anaerobic energy metabolism characteristic of amino acid-fermenting bacteria.
  • Iron availability in inflammatory environments may favor Acidaminococcus expansion alongside other iron-dependent pathobionts.

Key Enzymes and Metabolic Features

  • Glutamate dehydrogenase: Initiates glutamate catabolism, converting glutamate to 2-oxoglutarate. This enzyme's activity determines how effectively Acidaminococcus can exploit glutamate as an energy source.
  • Glutaconyl-CoA decarboxylase: A biotin-dependent sodium pump that couples glutamate fermentation to ATP synthesis via a sodium gradient. This energy-conserving strategy is the metabolic hallmark of the genus and explains its specificity for glutamate-rich environments.
  • Acetate and butyrate production: End products of glutamate fermentation include acetate and butyrate, though the overall metabolic impact may differ from fiber-derived SCFA production.

Ecological Role

In the Healthy Gut

Acidaminococcus is a minor member of the healthy gut microbiota, typically present at low abundance. Its niche — glutamate fermentation — is relatively specialized and does not compete directly with the dominant fiber-fermenting bacteria.

In Dysbiosis

Acidaminococcus expands in conditions characterized by:

  • Increased luminal amino acid availability (protein maldigestion, mucosal damage releasing tissue-derived amino acids)
  • Reduced competition from fiber fermenters (low-fiber Western diets eliminate the dominant SCFA-producing competitors)
  • Inflammatory environments where iron release from damaged tissue supports iron-dependent metabolism

Conditions Associated

Breast Cancer

Acidaminococcus is enriched in breast cancer patients (24% prevalence vs. 9% in controls), alongside hungatella and tyzzerella. Notably, Acidaminococcus-positive participants had significantly lower whole fruit intake (HEI-2015 scores, p = 0.005) altinok dindar 2023 gut microbiota breast cancer diet, connecting dietary patterns to pathobiont expansion.

Schizophrenia

Consistently up-regulated in schizophrenia across multiple studies in a systematic vote-counting meta-analysis, alongside prevotella, Succinivibrio, and other taxa li 2024 alterations gut microbiota schizophrenia vote counting.

Type 2 Diabetes

Identified as a key disease-discriminating taxon (absolute R-value > 0.6) in a multi-omics study of the gut microbiome-metabolome axis in T2D patients al bataineh 2023 multi omics microbiome metabolome t2d fiber.

COVID-19 Recovery

Acidaminococcus massiliensis was a key predictive feature in a random forest model distinguishing COVID-19 recovery status (AUC 0.99). Dynamic cycling was observed: enriched at baseline and 6 months but absent at 3 months, suggesting fluctuating dominance during immune reconstitution li 2025 long term gut microbiota alterations covid recovery.

Key Studies

Cross-References

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