title: A mutation in rcsB, a gene encoding the core component of the Rcs cascade, enhances the virulence of Edwardsiella tarda.
abstract: Edwardsiella tarda, a Gram-negative bacterium of the family Enterobacteriaceae, is the causative agent of the systemic disease edwardsiellosis, which is a major problem in aquaculture industry worldwide. Many virulence-related genes in E. tarda have been investigated, but the Rcs phosphorelay, a two-component pathway, which regulates several cell-surface-associated structures related to invasion and survival in host cells, has not yet been thoroughly studied. In the present study, an rcsB in-frame deletion mutant ΔrcsB was constructed through double-crossover allelic exchange. To complement the rcsB mutation, the ΔrcsB (pACYC184K-rcsB) mutant was constructed by transformation of a low-copy plasmid carrying the intact rcsB into the ΔrcsB mutant of E. tarda. Several virulence-associated characters of the mutants and wild-type strain were tested. Compared with wild-type strain EIB202, biofilm formation decreased significantly in ΔrcsB, while ΔrcsB (pACYC184K-rcsB) recovered the phenotype to some extent. In addition, the capacity for autoagglutination, the percentage of adherence and internalization to Epithelioma papulosum cyprini cells and lethality toward zebrafish embryos significantly increased in ΔrcsB. All these phenomena displayed by mutant ΔrcsB showed a certain degree of recovery, though incomplete, in strain ΔrcsB (pACYC184K-rcsB). Present results indicate that rcsB is involved in regulating the gene expression of virulence factors in E. tarda, as shown in other members of Enterobacteriaceae.
authors.affiliation: College of Marine Life Sciences, Ocean University of China, 5 Yushan Road, Qingdao 266003, PR China. Electronic address: 549357613@qq.com.
authors.forename: Ying
authors.initials: Y
authors.lastname: Xu
authors.affiliation: College of Marine Life Sciences, Ocean University of China, 5 Yushan Road, Qingdao 266003, PR China. Electronic address: xutingtingno1@163.com.
authors.forename: Tingting
authors.initials: T
authors.lastname: Xu
authors.affiliation: College of Marine Life Sciences, Ocean University of China, 5 Yushan Road, Qingdao 266003, PR China. Electronic address: sinowb@outlook.com.
authors.forename: Bin
authors.initials: B
authors.lastname: Wang
authors.affiliation: College of Marine Life Sciences, Ocean University of China, 5 Yushan Road, Qingdao 266003, PR China. Electronic address: dongxue0708@126.com.
authors.forename: Xue
authors.initials: X
authors.lastname: Dong
authors.affiliation: School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao 266003, PR China. Electronic address: sdytlzsab@163.com.
authors.forename: Aibo
authors.initials: A
authors.lastname: Sheng
authors.affiliation: College of Marine Life Sciences, Ocean University of China, 5 Yushan Road, Qingdao 266003, PR China. Electronic address: xhzhang@ouc.edu.cn.
authors.forename: Xiao-Hua
authors.initials: XH
authors.lastname: Zhang
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development; D002460:Cell Line; D004195:Disease Models, Animal; D020609:Edwardsiella tarda / Q000235:genetics* / Q000472:pathogenicity* / Q000502:physiology; D004756:Enterobacteriaceae Infections / Q000382:microbiology; D004847:Epithelial Cells / Q000382:microbiology; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D016019:Survival Analysis; D037521:Virulence Factors / Q000235:genetics* / Q000378:metabolism*; D015027:Zebrafish
chemical_list: D001426:Bacterial Proteins; D037521:Virulence Factors; C074889:RcsB protein, Bacteria
keywords: Edwardsiella tarda; In-frame deletion; Virulence; rcsB