Comparison of Japanese and Indian intestinal microbiota shows diet-dependent interaction between bacteria and fungi.

The bacterial species living in the gut mediate many aspects of biological processes such as nutrition and activation of adaptive immunity. In addition, commensal fungi residing in the intestine also influence host health. Although the interaction of bacterium and fungus has been shown, its precise mechanism during colonization of the human intestine remains largely unknown. Here, we show interaction between bacterial and fungal species for utilization of dietary components driving their efficient growth in the intestine. Next generation sequencing of fecal samples from Japanese and Indian adults revealed differential patterns of bacterial and fungal composition. In particular, Indians, who consume more plant polysaccharides than Japanese, harbored increased numbers of and . spp. showed strong growth responses to the plant polysaccharide arabinoxylan in vitro. Furthermore, the culture supernatants of spp. grown with arabinoxylan promoted rapid proliferation of . Arabinose was identified as a potential growth-inducing factor in the culture supernatants. spp. exhibited a growth response to xylose, but not to arabinose, whereas proliferated in response to both xylose and arabinose. spp., but not , colonized the intestine of germ-free mice. However, successfully colonized mouse intestine already harboring . These findings demonstrate a proof of concept that fungal members of gut microbiota can facilitate a colonization of the intestine by their bacterial counterparts, potentially mediated by a dietary metabolite.