The serine protease autotransporter Tsh contributes to the virulence of Edwardsiella tarda.
The temperature-sensitive hemagglutinin (Tsh), identified as serine protease autotransporters of the Enterobacteriaceae (SPATEs) proteins, is an important virulence factor for avian-pathogenic Escherichia coli (APEC) and uropathogenic E. coli. However, little is known about the role of Tsh as a virulence factor in Edwardsiella tarda, a severe fish pathogen. In this study, we characterized the Tsh of E. tarda (named TshEt) and examined its function and vaccine potential. TshEt is composed of 1224 residues and has three functional domains typical for autotransporters. Quantitative real-time reverse transcriptase-PCR analysis showed that expression of tshEt was upregulated under conditions of high temperature, increased cell density, high pH, and iron starvation and during the infection of host cells. A markerless tsh in-frame mutant strain, TX01Δtsh, was constructed to determine whether TshEt participates in the pathogenicity of E. tarda, Compared to the wild type TX01, TX01Δtsh exhibited (i) retarded biofilm growth, (ii) decreased resistance against serum killing, (iii) impaired ability to block the host immune response, (iv) attenuated tissue and cellular infectivity. Introduction of a trans-expressed tsh gene restored the lost virulence of TX01Δtsh. The passenger domain of TshEt contains a putative serine protease (PepS) that exhibits apparent proteolytic activity when expressed in and purified from E. coli as a recombinant protein (rPepS). When used as a subunit vaccine to immunize Japanese flounder, rPepS was able to induce effective immune protection. This is the first study of Tsh in a fish pathogen, and the results suggest that TshEt exerts pleiotropic effects on the pathogenesis of E. tarda.
Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China.
Yong-Hua
YH
Hu
Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Hai-Zhen
HZ
Zhou
Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Qian-Wen
QW
Jin
Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China. Electronic address: zhangjian@qdio.ac.cn.
Jian
J
Zhang
D000818:Animals; D001428:Bacterial Vaccines / Q000276:immunology; D020609:Edwardsiella tarda / Q000201:enzymology* / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity*; D004926:Escherichia coli / Q000235:genetics; D005432:Flounder / Q000276:immunology / Q000382:microbiology; D015964:Gene Expression Regulation, Bacterial; D054884:Host-Pathogen Interactions; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology; D057057:Serine Proteases / Q000235:genetics / Q000276:immunology*; D000069320:Type V Secretion Systems / Q000235:genetics* / Q000276:immunology; D014774:Virulence / Q000235:genetics* / Q000276:immunology; D037521:Virulence Factors / Q000235:genetics / Q000276:immunology*
D001428:Bacterial Vaccines; D011994:Recombinant Proteins; D000069320:Type V Secretion Systems; D037521:Virulence Factors; D057057:Serine Proteases
Autotransporter; Edwardsiella tarda; Fish pathogen; Tsh; Virulence