Cell & Molecular Biology Program Event
Ms. Kelly Fimlaid
Microbiology & Molecular Genetics
University of Vermont
A novel bifurcated pathway regulates sporulation in Clostridium difficile
Tuesday December 11th, 2012
The Gram-positive, spore-forming pathogen Clostridium difficile is the leading cause of hospital-acquired diarrhea worldwide. A major hallmark of C. difficile infections is their frequent recurrence, which can lead to life-threatening complications such as pseudomembranous colitis. C. difficile spores are the major form of transmission and responsible for these high rates of recurrence, since they are inert to antibiotics and resist common disinfectants. Despite the importance of spores to C. difficile pathogenesis, little is known about their composition or formation. In the model spore-former Bacillus subtilis, sporulation is coordinated by the sequential activation of the sigma factors F, E, G, and K, which control the transcription of genes required for spore maturation. To obtain a comprehensive snapshot of genes induced during spore assembly, we generated mutants in genes encoding the sporulation sigma factors E, G, and K and determined their regulons using RNA-Seq. From these studies, we identified 262 genes that are activated during spore formation of which 151 are E-dependent, 30 are G-dependent, and 34 are K-dependent. Further transcriptional and proteomic analyses revealed that the regulation of sporulation in C. difficile deviates significantly from that of B. subtilis, with a novel bifurcating pathway controlling sporulation sigma factor activation in C. difficile rather than a linear pathway. Collectively, these results provide the first integrated overview of sporulation gene expression in the Clostridia and reveal that diverse regulatory programs control spore formation in the Firmicutes.