Characterization of Edwardsiella tarda waaL: roles in lipopolysaccharide biosynthesis, stress adaptation, and virulence toward fish |
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Authors: | Lili Xu Qiyao Wang Jingfan Xiao Qin Liu Xin Wang Tao Chen Yuanxing Zhang |
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Institution: | (1) State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 200237 Shanghai, People’s Republic of China; |
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Abstract: | Edwardsiella tarda is the causative agent of edwardsiellosis in fish. The genome sequence of a virulent strain EIB202 has been determined. According
to the genome sequence, the lipopolysaccharide (LPS) synthesis cluster containing a putative O-antigen ligase gene waaL was identified. Here, the in-frame deletion mutant ΔwaaL was constructed to analyze the function of WaaL in E. tarda EIB202. The ΔwaaL mutant displayed absence in O-antigen side chains in the LPS production. The ΔwaaL mutant exhibited an increased sensitivity to hydrogen peroxide indicating that the LPS was involved in the endurance to the
oxidative stress in hosts during infection. In addition, the resistance of ΔwaaL to serum and polymyxin B decreased remarkably. The ΔwaaL mutant was also attenuated in virulence, showed an impaired ability in internalization of epithelioma papulosum cyprinid
(EPC) cells and a comparatively poor ability of proliferation in vivo, which was in line with the increased LD50 value. These results indicated that waaL gene was a functional member of the gene cluster involved in LPS synthesis and highlighted the importance of the O-antigen
side chains to stress adaption and virulence in E. tarda, signifying the gene as a potential target for live attenuated vaccine against this bacterium. |
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