Epigenetics and the microbiome

The gut-resident commensal microbial ecosystem, collectively termed the microbiome, plays a vital role in host physiology and disease susceptibility. Being strategically situated in the intersection between the host and the external environment, the microbiome serves as a hub which integrates dietary and other environmental signals with a multitude of inherent host signals, and forms extensive communication networks with the host. Disruption of the delicate balance between the host and its microbiome can result in alterations in microbial composition, termed dysbiosis, which is associated with the etiology of multiple pathologies including metabolic disorders, inflammatory diseases, cancer, and neurodegeneration. Most mechanisms mediating these microbial effects on the host remain elusive. Microbial-induced host epigenetic modifications have been recently suggested as one such mechanism, by which the microbiome translates environmental signals to fine-tuning of the host gene expression and subsequently its corresponding systemic functions. In this chapter, we highlight recently studied examples exploring the mechanisms by which the microbiome may elicit epigenetic changes in the host, thereby affecting its physiology and pathology.