Harry Kathryn H, Zhou Ruanbao, Kroos Lee, Melville Stephen B
Department of Biological Sciences, 2119 Derring Hall, Virginia Tech University, Blacksburg, VA 24061, USA.
J Bacteriol. 2009 Apr;191(8):2728-42. doi: 10.1128/JB.01839-08. Epub 2009 Feb 6.
Clostridium perfringens is the third most frequent cause of bacterial food poisoning annually in the United States. Ingested C. perfringens vegetative cells sporulate in the intestinal tract and produce an enterotoxin (CPE) that is responsible for the symptoms of acute food poisoning. Studies of Bacillus subtilis have shown that gene expression during sporulation is compartmentalized, with different genes expressed in the mother cell and the forespore. The cell-specific RNA polymerase sigma factors sigma(F), sigma(E), sigma(G), and sigma(K) coordinate much of the developmental process. The C. perfringens cpe gene, encoding CPE, is transcribed from three promoters, where P1 was proposed to be sigma(K) dependent, while P2 and P3 were proposed to be sigma(E) dependent based on consensus promoter recognition sequences. In this study, mutations were introduced into the sigE and sigK genes of C. perfringens. With the sigE and sigK mutants, gusA fusion assays indicated that there was no expression of cpe in either mutant. Results from gusA fusion assays and immunoblotting experiments indicate that sigma(E)-associated RNA polymerase and sigma(K)-associated RNA polymerase coregulate each other's expression. Transcription and translation of the spoIIID gene in C. perfringens were not affected by mutations in sigE and sigK, which differs from B. subtilis, in which spoIIID transcription requires sigma(E)-associated RNA polymerase. The results presented here show that the regulation of developmental events in the mother cell compartment of C. perfringens is not the same as that in B. subtilis and Clostridium acetobutylicum.
产气荚膜梭菌是美国每年细菌性食物中毒的第三大常见病因。摄入的产气荚膜梭菌营养细胞在肠道中形成芽孢,并产生一种肠毒素(CPE),该毒素导致急性食物中毒症状。枯草芽孢杆菌的研究表明,芽孢形成过程中的基因表达是分区进行的,不同的基因在母细胞和前芽孢中表达。细胞特异性RNA聚合酶σ因子σ(F)、σ(E)、σ(G)和σ(K)协调了大部分发育过程。编码CPE的产气荚膜梭菌cpe基因从三个启动子转录,根据共有启动子识别序列,P1被认为依赖于σ(K),而P2和P3被认为依赖于σ(E)。在本研究中,向产气荚膜梭菌的sigE和sigK基因中引入了突变。对于sigE和sigK突变体,gusA融合分析表明,两个突变体中均无cpe表达。gusA融合分析和免疫印迹实验结果表明,与σ(E)相关的RNA聚合酶和与σ(K)相关的RNA聚合酶相互调节彼此的表达。产气荚膜梭菌中spoIIID基因的转录和翻译不受sigE和sigK突变的影响,这与枯草芽孢杆菌不同,在枯草芽孢杆菌中,spoIIID转录需要与σ(E)相关的RNA聚合酶。此处给出的结果表明,产气荚膜梭菌母细胞区室中发育事件的调控与枯草芽孢杆菌和丙酮丁醇梭菌不同。