Small RNAs as emerging regulators of commensal adaptation in the mammalian gut

The commensal bacteria of the intestinal microbiota inhabit one of the most densely populated and dynamic microbial ecosystems known, where fluctuations in nutrient availability, host-derived stresses, and microbial competition require highly coordinated regulatory responses to maintain colonization and fitness. As a stable, homeostatic microbiota performs essential functions for the host, understanding how commensals adapt to the fluctuating intestinal environment is important for maintaining intestinal homeostasis and informing the development of new microbiota-targeted therapeutics. Throughout diverse bacterial species, rapid adaptation to environmental perturbations is mediated in part by small regulatory RNAs (sRNAs). While most sRNA research has focused on a limited number of model organisms, particularly bacterial pathogens, recent studies have uncovered important roles for these noncoding RNAs in promoting the fitness and resilience of gut commensals. Advances in differential RNA sequencing, comparative genomics, and functional genetics have revealed diverse repertoires of sRNAs in prominent gut symbionts, with regulatory roles in nutrient acquisition, stress responses, and host colonization. This minireview highlights recent advances and outlines future directions to further elucidate sRNA-mediated regulation as a pillar of commensal resilience in the mammalian gut.