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Characterization of Edwardsiella Tard RpoN: Roles in σ70 Family Regulation, Growth, Stress Adaption and Virulence Toward Fish

Author: WangKePing
Tutor: ZhangHuiZhan
School: East China University of Science and Technology
Course: Biochemistry and Molecular Biology
Keywords: Edwardsiella tarda rpoN biofilm formation virulence
CLC: Q933
Type: Master's thesis
Year: 2012
Downloads: 55
Quote: 0
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Abstract


Edwardsiella tarda EIB202, a gram-negative pathogen with strong virulence, is an opportunistic pathogen capable of causing edwardsiellosis with high mortality to fish. As a fish pathogen, E. tarda has been recognized as one of the most important aquaculture pathogens, because of its ability to infect a large variety of cultured fish species worldwide. Alternative sigma factor 54 (RpoN) is an important regulator of virulence and stress resistance genes in many bacterial species, and mainly responsible for transcription of genes in nitrogen utilization.In this study, the in-frame rpoN deletion mutant was constructed to analyze the function of RpoN in Edwardsiella tarda firstly. Compared to the wild type and complemented strain rpoN+, the ArpoN was impaired in terms of the ability to survive under oxidative stress, osmotic stress and acid resistance, as well as the growth in Luria-Bertani medium, demonstrating essential roles of RpoN in stress resistance and nitrogen utilization. In addition, the△rpoN displayed markedly decreased biofilm formation and chondroitinase activity, and was attenuated in virulence reflected in the increased median lethal dose value and extended infection cycle. Real-time polymerase chain reaction revealed that the expression levels ofσ70 class changed in varying degrees in the rpoN mutant. Especially, the expression levels of rpoS and fliA were down-regulated 4.1-fold and 7.9-fold in stationary phase in comparison to the wild type, respectively. Furthermore, two differential expression genes, znuA and flhC, were detected in the wild type and△rpoN using the method of differential display reverse transcription PCR.

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CLC: > Biological Sciences > Microbiology > Microbial Genetics
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