The Epigenetic Impact of the Human Microbiota on Host Cells

The human body harbors a microbial community that rivals the number of eukaryotic cells. Termed the human microbiota, this diverse population of microorganisms resides in various anatomical locations, such as the gut, oral cavity, respiratory tract, skin, and vagina. Advanced sequencing technologies have unveiled a significant portion of the microbiota as unculturable, expanding our understanding of the abundance, diversity, and functions of its microbial constituents. The extensively studied intestinal microbiome, for instance, is estimated to host a staggering 3 million bacterial genes, surpassing human genome protein-encoding genes by 100–150 times. Modern research highlights microbial metabolites’ role in modulating gene expression in eukaryotic cells through various mechanisms. Notably, epigenetically mediated changes in gene expression have emerged as a rapidly expanding interdisciplinary field. These epigenetic modifications exert biological effects both locally and at distant sites. They play a pivotal role in signaling along multiple gut–organ axes, including the gut–brain, gut–skin, and gut–lung axes. Consequently, they contribute significantly to the microbiota’s capacity to influence various intestinal and extraintestinal pathologies. A comprehensive understanding of microbiota-induced epigenetic changes in eukaryotic host cells holds the promise of unveiling intricate details about physiological processes and disease pathogenesis. This knowledge has the potential to identify new biomarkers and foster the development of novel therapeutic options.