Integrative genomic reconstruction reveals heterogeneity in carbohydrate utilization across human gut bifidobacteria

Bifidobacteria are beneficial saccharolytic microbes that are widely used as probiotics or in synbiotic formulations, yet individual responses to supplementation can vary with strain type, microbiota composition, diet and lifestyle, underscoring the need for strain-level insights into glycan metabolism. Here we reconstructed 68 pathways for the utilization of mono-, di-, oligo- and polysaccharides by analysing the distribution of 589 curated metabolic gene functions (catabolic enzymes, transporters and transcriptional regulators) across 3,083 non-redundant Bifidobacterium genomes of human origin. Thirty-eight predicted phenotypes were validated in vitro for 30 geographically diverse strains, supporting genomics-based predictions. Our analysis uncovered extensive inter- and intraspecies functional heterogeneity, including a distinct clade within Bifidobacterium longum that metabolizes α-glucans and Bangladeshi isolates carrying unique gene clusters for xyloglucan and human milk oligosaccharide utilization. This large-scale genomic compendium advances our understanding of bifidobacterial carbohydrate metabolism and can inform the rational design of probiotic and synbiotic formulations tailored to strain-specific nutrient preferences.