Clostridium difficile is a leading cause of antibiotic-associated diarrhea. The mechanisms underlying C. difficile expansion after microbiota disturbance are just emerging. We assessed the gene expression profile of C. difficile within the intestine of gnotobiotic mice to identify genes regulated in response to either dietary or microbiota compositional changes. In the presence of the gut symbiont Bacteroides thetaiotaomicron, C. difficile induces a pathway that metabolizes the microbiota fermentation end-product succinate to butyrate. The low concentration of succinate present in the microbiota of conventional mice is transiently elevated upon antibiotic treatment or chemically induced intestinal motility disturbance, and C. difficile exploits this succinate spike to expand in the perturbed intestine. A C. difficile mutant compromised in succinate utilization is at a competitive disadvantage during these perturbations. Understanding the metabolic mechanisms involved in microbiota-C. difficile interactions may help to identify approaches for the treatment and prevention of C. difficile-associated diseases. Display omitted •Biassociation with a gut symbiont induces a C. difficile succinate-utilization operon•Succinate accumulates in the gut upon antibiotic treatment or motility disturbance•Succinate utilization enables C. difficile expansion in the perturbed gut•A C. difficile mutant compromised in succinate utilization is colonization defective Nutrient resource partitioning by gut microbes is typically efficient. Ferreyra et al. demonstrate that upon antibiotic treatment or motility disturbance, succinate, an interspecies metabolic intermediate, transiently spikes to high levels. C. difficile induces a succinate-to-butyrate conversion pathway to take advantage of the succinate spike and expand during these gut perturbations.