Edwardsiella tarda EsaE (Orf19 protein) is required for the secretion of type III substrates, and pathogenesis in fish.
Type III secretion system (T3SS) is a large macromolecular assembly found on the surface of many pathogenic Gram-negative bacteria. Edwardsiella tarda is an important Gram-negative pathogen that employs T3SS to deliver effectors into host cells to facilitate its survival and replication. EseB, EseC, and EseD, when secreted, form a translocon complex EseBCD on host membranes through which effectors are translocated. The orf19 gene (esaE) of E. tarda is located upstream of esaK, and downstream of esaJ, esaI, esaH and esaG in the T3SS gene cluster. When its domains were searched using Delta-Blast, the EsaE protein was found to belong to the T3SS YscJ/PrgK family. In the present study, it is found that EsaE is not secreted into culture supernatant, and the deletion of esaE abolished the secretion of T3SS translocon proteins EseBCD and T3SS effector EseG. Increased steady-state protein level of EseC and EseD was detected in bacterial pellet of ΔesaE strain although a reduced level was observed for the eseC and eseD transcription. EsaE was found to localize on membrane but not in the cytoplasm of E. tarda by fractionation. In blue gourami fish infection model, 87.88% of blue gourami infected with ΔesaE strain survived whereas only 3.03% survived when infected with wild-type strain. Taken together, our study demonstrated that EsaE is probably an apparatus protein of T3SS, which contributes to the pathogenesis of E. tarda in fish.
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Ying
Y
Zhou
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province 430072, China.
Lu Yi
LY
Liu
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Tian Tian
TT
He
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Zubair Ahmed
ZA
Laghari
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province 430072, China.
Pin
P
Nie
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province 430072, China.
Qian
Q
Gao
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province 430072, China. Electronic address: xieh@ihb.ac.cn.
Hai Xia
HX
Xie
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D058947:Bacterial Secretion Systems / Q000235:genetics* / Q000378:metabolism*; D020609:Edwardsiella tarda / Q000235:genetics / Q000472:pathogenicity; D004756:Enterobacteriaceae Infections / Q000382:microbiology / Q000503:physiopathology / Q000662:veterinary*; D005393:Fish Diseases / Q000382:microbiology / Q000503:physiopathology*; D017353:Gene Deletion; D014774:Virulence / Q000235:genetics*
D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems
Edwardsiella tarda; EsaE (Orf19 protein); Type III secretion system; Virulence