Figure 5.

A model wherein the mammalian gut microbiota mediates communication between environmental exposures and host epigenetic programming of downstream phenotypes. Environmental exposures known to affect mammalian microbiota include: antibiotics, cold exposure, hormones, natural seasonal cycles in ambient temperature and food sources, and dietary composition, excess, and scarcity. The composition of the mammalian gut microbiota, which resides in the host alimentary tract and is in direct contact with the environment, is altered in response to environmental factors. Alteration of microbial community composition leads to differences in microbial metabolite production, and ultimately altered chemical signaling to host chromatin. Modifications to host chromatin then drive new transcriptional programs to produce an adapted phenotype. The proposed cycle may repeat in response to continued exposure to the same environmental factor or in response to a new exposure.