Overview
Parabacteroides distasonis is a Gram-negative obligate anaerobe formerly classified within Bacteroides. It is a core member of the healthy human gut microbiome, typically found in the colon where it contributes to polysaccharide degradation and bile acid metabolism.
Metal Dependencies
P. distasonis requires iron for central metabolic enzymes and zinc for its hydrolase activities. Paradoxically, the iron-rich inflammatory environments that favor Proteobacteria tend to suppress P. distasonis, suggesting it is outcompeted when nutritional immunity breaks down and luminal iron rises.
Ecological Role
In a balanced gut, P. distasonis performs critical bile acid biotransformations through bile salt hydrolase activity, converting primary bile acids to secondary forms that regulate host metabolism and immune signaling. Its depletion shifts the bile acid pool toward pro-inflammatory and pro-tumorigenic profiles. The organism also produces short-chain fatty acids that support epithelial barrier integrity.
Conditions Associated
Depletion of P. distasonis is consistently reported in obesity, type 2 diabetes, and inflammatory bowel disease. Animal studies show that oral supplementation with P. distasonis reduces adiposity, improves glucose tolerance, and attenuates intestinal inflammation — positioning it as a candidate next-generation probiotic.
Cross-References
- bile acid metabolism — bile salt hydrolase activity
- iron — growth requirement, competitive disadvantage in iron-excess
- short chain fatty acids — metabolic output
- obesity — depleted in metabolic disease