Adaptations of gummivorous primate gut-associated bifidobacteria to type-II arabinogalactan utilisation

Bifidobacteria inhabiting the primate gut exhibit host-dependent genetic diversification, particularly in their gene repertoire related to carbohydrate metabolism, suggesting adaptation to host diets. However, these diverse genetic traits remain poorly associated with specific dietary components. Here, through enzymatic and genetic analyses, we demonstrate that several Bifidobacterium species residing in the gut of gummivorous primates, such as marmosets, possess previously uncharacterised pathways for the efficient utilisation of type-II arabinogalactan (AG), the major polysaccharide component of tree gums. The assimilation pathways comprises two key components: a bifunctional β-1,3-galactanase that cleaves the AG backbone via both endo- and exo-mode actions and an ATP-binding cassette transporter that internalises the released arabinogalactan oligosaccharides (AGOs) into cells. Data mining of deposited metagenomic datasets suggested that the endo/exo-β-1,3-galactanase and the AGO transporter contribute to cross-feeding interactions within Bifidobacterium communities in the gut of gummivorous primates. Our study not only highlights molecular strategies employed by certain Bifidobacterium species to adapt to the dietary habits of a host but may also inform probiotic intervention strategies for the health and welfare of these primates in captive settings.