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

Members of the class <i>Clostridia</i>, a polyphyletic group of pathogenic and beneficial Gram-positive, spore-forming anaerobes in the <i>Bacillota</i> (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 <i>Anaerostipes</i>, a prevalent butyrate-producing genus within the gut microbiota. We conducted a genomic comparison across 21 <i>Anaerostipes</i> strains isolated from healthy human faecal samples (<i>n</i>=5) and publicly available genomes (<i>n</i>=105). Whole genome comparisons across the <i>Anaerostipes</i> genus demonstrated 12 species bins, clustering into three major functionally distinct clusters correlating with host origin. One cluster (representing mostly <i>Anaerostipes caccae</i> 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 (<i>Anaerostipes hadrus</i>, <i>A. caccae</i> and <i>Anaerostipes hominis</i>). Collectively, these data indicate genomic metabolic variance across <i>Anaerostipes</i> species that may influence coexistence within the gut environment and variably influence health.