Fig. 1.

Cocolonization with M. smithii (Ms) and B. thetaiotaomicron (Bt) enhances the representation of both species in the distal intestines of gnotobiotic mice. The density of colonization was defined by using quantitative PCR of DNA isolated from the cecal contents of monoassociated and biassociated mice (n = 5 per group per experiment; three independent experiments; each sample assayed in triplicate; mean values ± SEM plotted); ∗, P < 0.05 vs. monoassociated controls. Bt and Bt + Ms represent the number of B. thetaiotaomicron cells present in mice colonized with Bt alone or with Bt + Ms, respectively; Ms and Ms + Bt represent the number of M. smithii cells present in mice colonized with Ms alone or with Ms + Bt, respectively.