Effect of Mutation on Sporulation in the Epidemic Strain R20291.

is an important nosocomial pathogen and the leading cause of hospital-acquired diarrhea. Antibiotic use is the primary risk factor for the development of -associated disease because it disrupts normally protective gut flora and enables to colonize the colon. damages host tissue by secreting toxins and disseminates by forming spores. The toxin-encoding genes, and , are part of a pathogenicity locus, which also includes the gene that codes for TcdR, an alternate sigma factor that initiates transcription of and genes. We created a mutant in epidemic-type strain R20291 in an attempt to identify the global role of . A site-directed mutation in affected both toxin production and sporulation in R20291. Spores of the mutant were more heat sensitive than the wild type (WT). Nearly 3-fold more taurocholate was needed to germinate spores from the mutant than to germinate the spores prepared from the WT strain. Transmission electron microscopic analysis of the spores also revealed a weakly assembled exosporium on the mutant spores. Accordingly, comparative transcriptome analysis showed many differentially expressed sporulation genes in the mutant compared to the WT strain. These data suggest that regulatory networks of toxin production and sporulation in strain R20291 re linked with each other. infects thousands of hospitalized patients every year, causing significant morbidity and mortality. spores play a pivotal role in the transmission of the pathogen in the hospital environment. During infection, the spores germinate, and the vegetative bacterial cells produce toxins that damage host tissue. Thus, sporulation and toxin production are two important traits of . In this study, we showed that a mutation in , the toxin gene regulator, affects both toxin production and sporulation in epidemic-type strain R20291.