Open AccessEha, a transcriptional regulator of hemolytic activity of Edwardsiella tarda
Author(s) -
Gao Daqing,
Cheng Jing,
Zheng Enjin,
Li Yuhong,
Shao Zeye,
Xu Zeyan,
Lu Chengping
Publication year - 2014
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/1574-6968.12420
Subject(s) - edwardsiella tarda , cytolysin , biology , mutant , escherichia coli , hemolysis , gene , wild type , regulator , microbiology and biotechnology , genetics , virulence , immunology
Hemolysis causes major symptoms such as the reddening skin and systemic hemorrhagic septicemia of diseased fish infected by Edwardsiella tarda . Cytolysin A (ClyA) is a pore‐forming cytotoxic protein encoded by the clyA gene in Escherichia coli K‐12. In this study, we observed that the heterologous expression of the eha gene from E. tarda could confer hemolytic activity upon a hemolytic‐silent E. coli strain. The transcription of clyA is positively controlled by the eha gene in E. tarda by RT‐PCR. We cloned and purified Eha protein which had shown preferential binding ability to the clyA sequences in its promoter region, as evidenced by gel shift assay. The eha controls the transcriptional start predominantly at 72 bp upstream in the clyA promoter region, as determined by primer extension assays. We suggest that Eha protein is a new positive regulator found in E. tarda . In addition, we constructed the eha mutant and complementary strains of E. tarda . The hemolytic activity of the eha mutant was found to be attenuated compared with the wild‐type strain. The complementary strains restored the hemolytic activity to levels between those of the wild type and the eha mutation. Our results indicate that the Eha protein is an important positive regulator in the hemolytic properties of E. tarda .