title: Identification and functional characterization of the novel Edwardsiella tarda effector EseJ.
abstract: Edwardsiella tarda is a Gram-negative enteric pathogen that causes hemorrhagic septicemia in fish and gastro- and extraintestinal infections in humans. The type III secretion system (T3SS) of E. tarda has been identified as a key virulence factor that contributes to pathogenesis in fish. However, little is known about the associated effectors translocated by this T3SS. In this study, by comparing the profile of secreted proteins of the wild-type PPD130/91 and its T3SS ATPase ΔesaN mutant, we identified a new effector by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry. This effector consists of 1,359 amino acids, sharing high sequence similarity with Orf29/30 of E. tarda strain EIB202, and is renamed EseJ. The secretion and translocation of EseJ depend on the T3SS. A ΔeseJ mutant strain adheres to epithelioma papillosum of carp (EPC) cells 3 to 5 times more extensively than the wild-type strain does. EseJ inhibits bacterial adhesion to EPC cells from within bacterial cells. Importantly, the ΔeseJ mutant strain does not replicate efficiently in EPC cells and fails to replicate in J774A.1 macrophages. In infected J774A.1 macrophages, the ΔeseJ mutant elicits higher production of reactive oxygen species than wild-type E. tarda. The replication defect is consistent with the attenuation of the ΔeseJ mutant in the blue gourami fish model: the 50% lethal dose (LD50) of the ΔeseJ mutant is 2.34 times greater than that of the wild type, and the ΔeseJ mutant is less competitive than the wild type in mixed infection. Thus, EseJ represents a novel effector that contributes to virulence by reducing bacterial adhesion to EPC cells and facilitating intracellular bacterial replication.
authors: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, China.
authors: Hai-Xia
authors: HX
authors: Xie
authors: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, China University of Chinese Academy of Sciences, Beijing, China.
authors: Jin-Fang
authors: JF
authors: Lu
authors: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, China University of Chinese Academy of Sciences, Beijing, China.
authors: Ying
authors: Y
authors: Zhou
authors: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, China University of Chinese Academy of Sciences, Beijing, China.
authors: Jia
authors: J
authors: Yi
authors: Section of Microbiology, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, United Kingdom x.yu@imperial.ac.uk pinnie@ihb.ac.cn.
authors: Xiu-Jun
authors: XJ
authors: Yu
authors: Department of Biology, Faculty of Natural and Applied Sciences, Trinity Western University, Langley, British Columbia, Canada State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, China.
authors: Ka Yin
authors: KY
authors: Leung
authors: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, China x.yu@imperial.ac.uk pinnie@ihb.ac.cn.
authors: Pin
authors: P
authors: Nie
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics; D000818:Animals; D001422:Bacterial Adhesion / Q000235:genetics* / Q000502:physiology; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D058947:Bacterial Secretion Systems / Q000235:genetics*; D002478:Cells, Cultured; D020609:Edwardsiella tarda / Q000235:genetics / Q000472:pathogenicity*; D004756:Enterobacteriaceae Infections; D005393:Fish Diseases / Q000382:microbiology; D005399:Fishes / Q000382:microbiology; D008264:Macrophages / Q000276:immunology* / Q000382:microbiology; D051379:Mice; D008969:Molecular Sequence Data; D040901:Proteomics; D017382:Reactive Oxygen Species / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D037521:Virulence Factors / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems; D017382:Reactive Oxygen Species; D037521:Virulence Factors; D000251:Adenosine Triphosphatases