Yasugi Mayo, Okuzaki Daisuke, Kuwana Ritsuko, Takamatsu Hiromu, Fujita Masaya, Sarker Mahfuzur R, Miyake Masami
Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Izumisano, Osaka, Japan
DNA Chip Development Center, RIMD, Osaka University, Suita, Osaka, Japan.
Appl Environ Microbiol. 2016 May 2;82(10):2929-2942. doi: 10.1128/AEM.00252-16. Print 2016 May 15.
Clostridium perfringens type A is a common source of foodborne illness (FBI) in humans. Vegetative cells sporulate in the small intestinal tract and produce the major pathogenic factor C. perfringens enterotoxin. Although sporulation plays a critical role in the pathogenesis of FBI, the mechanisms inducing sporulation remain unclear. Bile salts were shown previously to induce sporulation, and we confirmed deoxycholate (DCA)-induced sporulation in C. perfringens strain NCTC8239 cocultured with human intestinal epithelial Caco-2 cells. In the present study, we performed transcriptome analyses of strain NCTC8239 in order to elucidate the mechanism underlying DCA-induced sporulation. Of the 2,761 genes analyzed, 333 were up- or downregulated during DCA-induced sporulation and included genes for cell division, nutrient metabolism, signal transduction, and defense mechanisms. In contrast, the virulence-associated transcriptional regulators (the VirR/VirS system, the agr system, codY, and abrB) were not activated by DCA. DCA markedly increased the expression of signaling molecules controlled by Spo0A, the master regulator of the sporulation process, whereas the expression of spo0A itself was not altered in the presence or absence of DCA. The phosphorylation of Spo0A was enhanced in the presence of DCA. Collectively, these results demonstrated that DCA induced sporulation, at least partially, by facilitating the phosphorylation of Spo0A and activating Spo0A-regulated genes in strain NCTC8239 while altering the expression of various genes.
Disease caused by Clostridium perfringens type A consistently ranks among the most common bacterial foodborne illnesses in humans in developed countries. The sporulation of C. perfringens in the small intestinal tract is a key event for its pathogenesis, but the factors and underlying mechanisms by which C. perfringens sporulates in vivo currently remain unclear. Bile salts, major components of bile, which is secreted from the liver for the emulsification of lipids, were shown to induce sporulation. However, the mechanisms underlying bile salt-induced sporulation have not yet been clarified. In the present study, we demonstrate that deoxycholate (one of the bile salts) induces sporulation by facilitating the phosphorylation of Spo0A and activating Spo0A-regulated genes using a transcriptome analysis. Thus, this study enhances our understanding of the mechanisms underlying sporulation, particularly that of bile salt-induced sporulation, in C. perfringens.
A型产气荚膜梭菌是人类食源性疾病（FBI）的常见病因。营养细胞在小肠中形成芽孢，并产生主要致病因子产气荚膜梭菌肠毒素。虽然芽孢形成在食源性疾病的发病机制中起关键作用，但诱导芽孢形成的机制仍不清楚。先前已证明胆汁盐可诱导芽孢形成，并且我们证实在与人类肠道上皮Caco-2细胞共培养的产气荚膜梭菌菌株NCTC8239中，脱氧胆酸盐（DCA）可诱导芽孢形成。在本研究中，我们对菌株NCTC8239进行了转录组分析，以阐明DCA诱导芽孢形成的潜在机制。在所分析的2761个基因中，有333个基因在DCA诱导芽孢形成过程中上调或下调，包括细胞分裂、营养代谢、信号转导和防御机制相关的基因。相比之下，毒力相关的转录调节因子（VirR/VirS系统、agr系统、codY和abrB）未被DCA激活。DCA显著增加了由芽孢形成过程的主调节因子Spo0A控制的信号分子的表达，而无论有无DCA，spo0A自身的表达均未改变。在DCA存在的情况下，Spo0A的磷酸化增强。总体而言，这些结果表明，DCA通过促进Spo0A的磷酸化和激活NCTC8239菌株中Spo0A调节的基因，同时改变各种基因的表达，至少部分地诱导了芽孢形成。
在发达国家，A型产气荚膜梭菌引起的疾病一直是人类最常见的细菌性食源性疾病之一。产气荚膜梭菌在小肠中的芽孢形成是其发病机制中的关键事件，但目前产气荚膜梭菌在体内形成芽孢的因素和潜在机制仍不清楚。胆汁盐是胆汁的主要成分，由肝脏分泌用于乳化脂质，已证明其可诱导芽孢形成。然而，胆汁盐诱导芽孢形成的潜在机制尚未阐明。在本研究中，我们通过转录组分析证明，脱氧胆酸盐（一种胆汁盐）通过促进Spo0A的磷酸化和激活Spo0A调节的基因来诱导芽孢形成。因此，本研究增进了我们对产气荚膜梭菌芽孢形成机制的理解，特别是胆汁盐诱导芽孢形成的机制。
