Genomic insights into the functional and metabolic versatility of gut microbiome Anaerostipes species.

Members of the class Clostridia, a polyphyletic group of pathogenic and beneficial Gram-positive, spore-forming anaerobes in the Bacillota (Firmicutes) phylum, are prevalent in the human gut. While this class includes select pathogens known to cause disease, many species are associated with beneficial functions, such as providing colonization resistance against pathogens. Despite a demonstrated value in maintaining Clostridial populations in the gut, functional strain diversity of most commensal Clostridial species remains understudied. Here, we isolated and characterized Clostridial isolates, focusing on the genomic diversity of Anaerostipes, a prevalent butyrate-producing genus within the gut microbiota. We conducted a genomic comparison across 21 Anaerostipes strains isolated from healthy human faecal samples (n=5) and publicly available genomes (n=105). Whole genome comparisons across the Anaerostipes genus demonstrated 12 species bins, clustering into three major functionally distinct clusters correlating with host origin. One cluster (representing mostly Anaerostipes caccae genomes) was distinguished by possessing a complete vitamin B12 biosynthesis pathway. Variability in genomic and phenotypic carbohydrate metabolism was demonstrated within dominant species of the human microbiota (Anaerostipes hadrus, A. caccae and Anaerostipes hominis). Collectively, these data indicate genomic metabolic variance across Anaerostipes species that may influence coexistence within the gut environment and variably influence health.