The Phosphotransfer Protein CD1492 Represses Sporulation Initiation in Clostridium difficile
The formation of spores is critical for the survival ofClostridium difficileoutside the host gastrointestinal tract. Persistence ofC. difficilespores greatly contributes to the spread ofC. difficileinfection (CDI), and the resistance of spores to antimicrobials facilitates the relapse of infection. Despite the importance of sporulation toC. difficilepathogenesis, the molecular mechanisms controlling spore formation are not well understood. The initiation of sporulation is known to be regulated through activation of the conserved transcription factor Spo0A. Multiple regulators influence Spo0A activation in other species; however, many of these factors are not conserved inC. difficileand few novel factors have been identified. Here, we investigated the function of a protein, CD1492, that is annotated as a kinase and was originally proposed to promote sporulation by directly phosphorylating Spo0A. We found that deletion ofCD1492resulted in increased sporulation, indicating that CD1492 is a negative regulator of sporulation. Accordingly, we observed increased transcription of Spo0A-dependent genes in theCD1492mutant. Deletion of CD1492 also resulted in decreased toxin productionin vitroand in decreased virulence in the hamster model of CDI. Further, theCD1492mutant demonstrated effects on gene expression that are not associated with Spo0A activation, including lowersigDandrstAtranscription, suggesting that this protein interacts with factors other than Spo0A. Altogether, the data indicate that CD1492 negatively affects sporulation and positively influences motility and virulence. These results provide further evidence thatC. difficilesporulation is regulated differently from that of other endospore-forming species.