Ecological specificity of the metagenome in a set of lower termite species supports contribution of the microbiome to adaptation of the host

Abstract

Elucidating the interplay between hosts and their microbiomes in ecological adaptation has become a central theme in evolutionary biology. The microbiome mediated adaptation of lower termites to a wood-based diet. Lower termites have further adapted to different ecologies. Substantial ecological differences are linked to different termite life types. Termites of the wood-dwelling life type never leave their nests and feed on a uniform diet. Termites of the foraging life type forage for food outside the nest, access a more diverse diet, and grow faster. Here we reasoned that the microbiome that is directly involved in food substrate breakdown and nutrient acquisition might contribute to adaptation to these ecological differences. This should leave ecological imprints on the microbiome. To search for such imprints, we applied metagenomic shotgun sequencing in a multispecies framework covering both life types. The microbiome of foraging species was enriched with genes for starch digestion, while the metagenome of wood-dwelling species was enriched with genes for hemicellulose utilization. Furthermore, increased abundance of genes for nitrogen sequestration, a limiting factor for termite growth, aligned with faster growth. These findings are consistent with the notion that a specific subset of functions encoded by the microbiome contributes to host adaptation.