Content area
Full Text
Curr Microbiol (2011) 62:492500
DOI 10.1007/s00284-010-9734-y
RpoE may Promote Flagellar Gene Expression in Salmonella enterica Serovar Typhi Under Hyperosmotic Stress
Hong Du Xiumei Sheng Haifang Zhang
Xin Zou Bin Ni Shungao Xu Xueming Zhu
Huaxi Xu Xinxiang Huang
Received: 27 February 2010 / Accepted: 23 July 2010 / Published online: 18 August 2010 Springer Science+Business Media, LLC 2010
Abstract Salmonella enterica serovar Typhi z66 positive strain contains a jBA-like operon on a linear plasmid. The operon contains the gene jB:z66 which encodes the z66 antigen. RpoE is a sigma factor rE that initiates transcription of a series of genes in Escherichia and Salmonella under environmental stresses. To investigate whether the gene jB:z66 is regulated by RpoE (rE), a rpoE deletion mutant of S. enterica serovar Typhi (DrpoE) was prepared in this study. The defective motility of the DrpoE was conrmed rstly. Transcriptional expression of agellar genes was screened using a genomic DNA microarray. Some class-2 and most class-3 agellar genes were downregulated in the DrpoE after 30 min of hyperosmotic stress. The expression of iA and jB:z66, a class-2 agellar gene and a class-3 agellar gene, obviously decreased; however, expression of the class-1 agellar genes hDC did not change obviously in the DrpoE compared to the wild-type strain in the same conditions. Results of quantitative real-time PCR (qRT-PCR) showed that the expression levels of iA and jB:z66 in the DrpoE after 30 min of hyperosmotic stress decreased about ve and eightfold, respectively, compared to the wild-type strain. Similar results were observed at 120 min of
hyperosmotic stress. Western blotting and qRT-PCR analysis showed that expression of iA and jB:z66 was signicantly increased after supplemental expression of rpoE with a recombinant plasmid pBADrpoE in the DrpoE strain. These results demonstrated that RpoE promoted the expression of class-3 agellar genes and it might be performed by initiating the expression of iA in S. enterica serovar Typhi under hyperosmotic stress.
Introduction
Flagellum is an important pathogenic factor that is essential for the motility of Salmonella. Approximately 50 genes are associated with agellar structure and function, and they are divided into three classes according to the regulation of transcription. The hDC operon lies at the top of the hierarchy as the sole class-1 operon, with both of its gene...