Small proteins link c-di-GMP signaling to sporulation control in Clostridioides difficile

Researchers identified a family of small membrane-associated proteins that link the bacterial signaling molecule c-di-GMP to the inhibition of spore formation in Clostridioides difficile, a pathogen responsible for severe intestinal infections. The proteins are encoded by genes controlled by c-di-GMP-responsive riboswitches, which repress their expression when c-di-GMP levels are high. Overexpressing one such gene triggered sporulation gene activation and increased spore production, while deleting all seven genes caused a severe sporulation defect, confirming their cumulative and redundant roles. This discovery clarifies the long-unclear mechanism by which c-di-GMP suppresses sporulation, a process essential for C. difficile's persistence and transmission. The findings establish these small proteins as key regulators of spore formation, offering a potential target for interventions against this healthcare-associated pathogen.