Analyzing the molecular foundations of commensalism in the mouse intestine

We maintain complex societies of nonpathogenic microbes on our mucosal surf aces. Although the stability of this flora is important for human health, v ery little is known about how its constituents communicate with us to forge stable and mutually advantageous relationships. The vast majority of these indigenous microbes reside in the intestine. Recent studies of a gut comme nsal, Bacteroides thetaiotaomicron, has revealed a novel signaling pathway that allows the microbe and host to actively collaborate to produce a nutri ent foundation that can be used by this bacterium. This pathway illustrates the type of dynamic molecular interactions that help define commensal rela tionships.