Figure 1.

Mechanisms by which host immune system mediates the crosstalk between gut microbiota and host physiology. Gut microbes exhibit diurnal oscillations, which in turn induce rhythmic sensing of bacterial cues through pattern recognition receptors. The microbial signals keep host circadian clock ticking, thereby maintaining homeostasis and enhancing physiological functions. clock shape circle, endogenous clock of immune cells and intestinal epithelium; circle with wave, schematic representation of diurnal oscillation.