Division of labor in honey bee gut microbiota for plant polysaccharide digestion

Honey bees and other social bees harbor specialized gut microbiota dominated by 5 coevolved bacterial clusters. Bees eat pollen, which contains diverse polysaccharides, energy-rich substrates potentially digested by gut bacteria. Polysaccharide degradation genes were identified in genome sequences of cultured bacteria and in metagenomic data, revealing that Bifidobacterium and Gilliamella digest polysaccharides in the honey bee gut. In both, individual strains vary in these abilities. Polysaccharide-degrading genes are clustered within Bifidobacterium genomes and are expressed in response to specific substrates. Other bee gut bacterial species cannot degrade polysaccharides, and some species rely on others for amino acids. This work provides insight into how bacterial species diverge into different ecological niches within the gut of their hosts.