title: Regulation of Clostridium difficile Spore Formation by the SpoIIQ and SpoIIIA Proteins.
abstract: Sporulation is an ancient developmental process that involves the formation of a highly resistant endospore within a larger mother cell. In the model organism Bacillus subtilis, sporulation-specific sigma factors activate compartment-specific transcriptional programs that drive spore morphogenesis. σG activity in the forespore depends on the formation of a secretion complex, known as the "feeding tube," that bridges the mother cell and forespore and maintains forespore integrity. Even though these channel components are conserved in all spore formers, recent studies in the major nosocomial pathogen Clostridium difficile suggested that these components are dispensable for σG activity. In this study, we investigated the requirements of the SpoIIQ and SpoIIIA proteins during C. difficile sporulation. C. difficile spoIIQ, spoIIIA, and spoIIIAH mutants exhibited defects in engulfment, tethering of coat to the forespore, and heat-resistant spore formation, even though they activate σG at wildtype levels. Although the spoIIQ, spoIIIA, and spoIIIAH mutants were defective in engulfment, metabolic labeling studies revealed that they nevertheless actively transformed the peptidoglycan at the leading edge of engulfment. In vitro pull-down assays further demonstrated that C. difficile SpoIIQ directly interacts with SpoIIIAH. Interestingly, mutation of the conserved Walker A ATP binding motif, but not the Walker B ATP hydrolysis motif, disrupted SpoIIIAA function during C. difficile spore formation. This finding contrasts with B. subtilis, which requires both Walker A and B motifs for SpoIIIAA function. Taken together, our findings suggest that inhibiting SpoIIQ, SpoIIIAA, or SpoIIIAH function could prevent the formation of infectious C. difficile spores and thus disease transmission.
authors.affiliation: 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.
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Fimlaid
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America.
authors.forename: Owen
authors.initials: O
authors.lastname: Jensen
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America.
authors.forename: M Lauren
authors.initials: ML
authors.lastname: Donnelly
authors.affiliation: Department of Microbiology, University of Massachusetts Amherst, Amherst, Massachusetts, United States of America.
authors.forename: M Sloan
authors.initials: MS
authors.lastname: Siegrist
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America.
authors.forename: Aimee
authors.initials: A
authors.lastname: Shen
mesh_terms: D000255:Adenosine Triphosphate / Q000235:genetics; D020816:Amino Acid Motifs / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics*; D002454:Cell Differentiation / Q000235:genetics; D002473:Cell Wall / Q000235:genetics; D016360:Clostridioides difficile / Q000235:genetics* / Q000472:pathogenicity; D004761:Enterocolitis, Pseudomembranous / Q000235:genetics* / Q000382:microbiology; D009154:Mutation; D011485:Protein Binding; D012808:Sigma Factor / Q000235:genetics*; D013171:Spores, Bacterial / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D012808:Sigma Factor; D000255:Adenosine Triphosphate