Overview
Parasutterella excrementihominis is a Gram-negative, obligately anaerobic bacterium that is increasingly recognized as a core member of the human gut microbiota. Despite being classified within the Proteobacteria phylum, which includes many well-known pathogens, P. excrementihominis is typically a low-abundance commensal that appears to play important roles in bile acid and purine metabolism. It was originally isolated from human feces and has since been identified as a consistent component of the healthy gut microbial community in over half of adults studied.
Classification
P. excrementihominis belongs to the family Sutterellaceae, order Burkholderiales, class Betaproteobacteria. It is closely related to the genus Sutterella but was designated as a separate genus based on distinct biochemical and genetic characteristics. The type strain YIT 11859 was isolated from human fecal samples and deposited in the DSMZ culture collection. Unlike many Proteobacteria that are facultatively anaerobic, Parasutterella is a strict anaerobe, reflecting its adaptation to the oxygen-depleted environment of the large intestine.
Key Characteristics
A distinguishing feature of P. excrementihominis is its involvement in bile acid and purine metabolism within the gut ecosystem. Research has demonstrated that increases in Parasutterella abundance correlate with changes in cholesterol metabolism, particularly LDL cholesterol levels. In intervention trials using resistant potato starch, individuals who showed increases in Parasutterella experienced significant decreases in LDL cholesterol. The organism also appears to respond to specific prebiotic supplementation, including resistant starch and galacto-oligosaccharides (GOS), suggesting it may be a target for dietary modulation strategies.
Health Significance
The health implications of P. excrementihominis appear to be context-dependent and multifaceted. On one hand, its association with LDL cholesterol reduction and responsiveness to prebiotic intervention suggest potential metabolic benefits. On the other hand, research has positively associated Parasutterella abundance with BMI and type 2 diabetes independently of reduced microbiome diversity, and it has been linked to dietary carbohydrate intake and altered fatty acid production. More recent studies suggest it may exacerbate experimental colitis in animal models and correlate with inflammatory bowel disease severity in clinical settings. This dual role as both a potential metabolic modulator and an IBD risk factor underscores the complexity of host-microbe interactions. P. excrementihominis may appear on comprehensive microbiome testing panels, where its relative abundance could provide insights into metabolic and inflammatory status.