Identification of a Novel Lipoprotein Regulator of Clostridium difficile Spore Germination.
Clostridium difficile is a Gram-positive spore-forming pathogen and a leading cause of nosocomial diarrhea. C. difficile infections are transmitted when ingested spores germinate in the gastrointestinal tract and transform into vegetative cells. Germination begins when the germinant receptor CspC detects bile salts in the gut. CspC is a subtilisin-like serine pseudoprotease that activates the related CspB serine protease through an unknown mechanism. Activated CspB cleaves the pro-SleC zymogen, which allows the activated SleC cortex hydrolase to degrade the protective cortex layer. While these regulators are essential for C. difficile spores to outgrow and form toxin-secreting vegetative cells, the mechanisms controlling their function have only been partially characterized. In this study, we identify the lipoprotein GerS as a novel regulator of C. difficile spore germination using targeted mutagenesis. A gerS mutant has a severe germination defect and fails to degrade cortex even though it processes SleC at wildtype levels. Using complementation analyses, we demonstrate that GerS secretion, but not lipidation, is necessary for GerS to activate SleC. Importantly, loss of GerS attenuates the virulence of C. difficile in a hamster model of infection. Since GerS appears to be conserved exclusively in related Peptostreptococcaeace family members, our results contribute to a growing body of work indicating that C. difficile has evolved distinct mechanisms for controlling the exit from dormancy relative to B. subtilis and other spore-forming organisms.
Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America; Program in Cellular, Molecular & Biomedical Sciences, University of Vermont, Burlington, Vermont, United States of America.
Kelly A
KA
Fimlaid
Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America.
Owen
O
Jensen
Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America.
M Lauren
ML
Donnelly
Department of Biology, Texas A&M University, College Station, Texas, United States of America.
Michael B
MB
Francis
Department of Biology, Texas A&M University, College Station, Texas, United States of America.
Joseph A
JA
Sorg
Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America.
Aimee
A
Shen
D000818:Animals; D001426:Bacterial Proteins / Q000502:physiology*; D002352:Carrier Proteins / Q000502:physiology; D016360:Clostridioides difficile / Q000502:physiology*; D006224:Cricetinae; D008074:Lipoproteins / Q000502:physiology*; D013171:Spores, Bacterial / Q000502:physiology
D001426:Bacterial Proteins; D002352:Carrier Proteins; C102917:CspC protein, Clostridium; D008074:Lipoproteins; C077188:cold-shock protein CspB, Bacteria