Christensenella minuta boosts gut microbial biomass and voluntary physical activity in mice

The gut bacteria of the family Christensenellaceae are consistently associated with metabolic health, but their role in promoting host health is not fully understood. We explored the effect of Christensenella minuta amendment on voluntary physical activity and the microbiome. We inoculated male and female germ-free mice with an obese human donor microbiota together with live or heat-killed C. minuta for 28 days and measured physical activity in respirometry cages. Compared to heat-killed, the live-C.minuta treatment resulted in reduced feed efficiency and higher levels of physical activity, with significantly greater distance traveled for males, and higher levels of small movements and resting metabolic rate in females. Sex-specific effects of C. minuta treatment may be in part attributed to different housing conditions for males and females. Amendment with live C. minuta boosted gut microbial biomass in both sexes, immobilizing dietary carbon in the microbiome, and we observed greater energy loss in stool. Live C. minuta also reduced within and between-host gut microbial diversity. Overall, our results showed that C. minuta acts as a keystone species: despite low relative abundance, it has a large impact on its ecosystem, from the microbiome to host energy homeostasis.