FIGURE 2.

Germ-free animals provide avenues for discovering microbiota-mediated effects of temperature on hosts. Rearing hosts at different ambient temperatures (Left), transplanting the hosts’ microbiota into germ-free animals (Center), and measuring responses in gnotobiotic recipients (Right) can identify effects of changes in the microbiota driven by ambient temperature on host phenotype. Experiments in mice have shown that cold-driven changes in the gut microbiota cause responses in host metabolism that improve host cold tolerance (Chevalier et al., 2015).