Metabolic adaption to extracellular pyruvate triggers biofilm formation in Clostridioides difficile.

Clostridioides difficile infections are associated with gut microbiome dysbiosis and are the leading cause of hospital-acquired diarrhoea. The infectious process is strongly influenced by the microbiota and successful infection relies on the absence of specific microbiota-produced metabolites. Deoxycholate and short-chain fatty acids are microbiota-produced metabolites that limit the growth of C. difficile and protect the host against this infection. In a previous study, we showed that deoxycholate causes C. difficile to form strongly adherent biofilms after 48 h. Here, our objectives were to identify and characterize key molecules and events required for biofilm formation in the presence of deoxycholate. We applied time-course transcriptomics and genetics to identify sigma factors, metabolic processes and type IV pili that drive biofilm formation. These analyses revealed that extracellular pyruvate induces biofilm formation in the presence of deoxycholate. In the absence of deoxycholate, pyruvate supplementation was sufficient to induce biofilm formation in a process that was dependent on pyruvate uptake by the membrane protein CstA. In the context of the human gut, microbiota-generated pyruvate is a metabolite that limits pathogen colonization. Taken together our results suggest that pyruvate-induced biofilm formation might act as a key process driving C. difficile persistence in the gut.