title: Overexpression of mltA in Edwardsiella tarda reduces resistance to antibiotics and enhances lethality in zebra fish.
abstract: OBJECTIVE
  The aim of this study was to investigate the role of membrane-bound lytic murein transglycosylase A (MltA) in a bacterial fish pathogen Edwardsiella tarda.
  
  
  RESULTS
  An mltA in-frame deletion mutant (ΔmltA) and an mltA overexpression strain (mltA(+)) of Edw. tarda were constructed through double-crossover allelic exchange and by transformation of a low-copy plasmid carrying the intact mltA into the ΔmltA mutant, respectively. Either inactivation or overexpression of MltA in Edw. tarda resulted in elevated sensitivity to β-lactam antibiotics and lower viability in oligotrophic or high osmotic environment than wild-type strain. Autolysis induced by EDTA was reduced in ΔmltA strain, while mltA(+) strain was virtually flimsy, indicating that MltA is responsible for the lysis effect. Moreover, mltA(+) strain exhibited significant increases in lipopolysaccharide (LPS) biosynthesis and virulence to zebra fish compared with wild-type strain.
  
  
  CONCLUSIONS
  The results indicated that MltA plays essential roles in β-lactam antibiotics and environmental stresses resistance, autolysis, LPS biosynthesis and pathogenicity of Edw. tarda. This is the first report that MltA has a virulence-related function in Edw. tarda.
  
  
  CONCLUSIONS
  This study provided useful information for further studies on pathogenesis of Edw. tarda.
authors.affiliation: College of Marine Life Sciences, Ocean University of China, Qingdao, China.
authors.forename: W
authors.initials: W
authors.lastname: Liu
authors.forename: N
authors.initials: N
authors.lastname: Dong
authors.forename: X-H
authors.initials: XH
authors.lastname: Zhang
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D020609:Edwardsiella tarda / Q000187:drug effects / Q000472:pathogenicity* / Q000502:physiology; D004756:Enterobacteriaceae Infections / Q000382:microbiology / Q000662:veterinary*; D005393:Fish Diseases / Q000382:microbiology*; D017353:Gene Deletion; D016695:Glycosyltransferases / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D014774:Virulence; D015027:Zebrafish; D047090:beta-Lactams / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D047090:beta-Lactams; D016695:Glycosyltransferases; C085441:MltA protein, bacteria