AUTHOR=Wang Jiajia , Xiu Lijun , Qiao Ying , Zhang Youyu 

TITLE=Virulence regulation of Zn2+ uptake system znuABC on mesophilic Aeromonas salmonicida SRW-OG1

JOURNAL=Frontiers in Veterinary Science

VOLUME=10

YEAR=2023

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2023.1172123

DOI=10.3389/fvets.2023.1172123

ISSN=2297-1769

ABSTRACT=<p>Psychrophilic <italic>Aeromonas salmonicida</italic> could not grow above 25°C and therefore thought unable to infect mammals and humans. In our previous study, a mesophilic <italic>A. salmonicida</italic> SRW-OG1 was isolated from <italic>Epinephelus coioides</italic> with furunculosis. Through the analysis of preliminary RNA-seq, it was found that the Zn<sup>2+</sup> uptake related genes <italic>znuA, znuB</italic> and <italic>znuC</italic> might be involved in the virulence regulation of <italic>A. salmonicida</italic> SRW-OG1. Therefore, the purpose of this study was to explore the effect of <italic>znuABC</italic> silencing on the virulence regulation of <italic>A. salmonicida</italic> SRW-OG1. The results showed that the growth of the <italic>znuA</italic>-RNAi, <italic>znuB</italic>-RNAi, and <italic>znuC</italic>-RNAi strains was severely restricted under the Fe<sup>2+</sup> starvation, but surprisingly there was no significant difference under the Zn<sup>2+</sup> restriction. In the absence of Zn<sup>2+</sup> and Fe<sup>2+</sup>, the expression level of <italic>znuABC</italic> was significantly increased. The motility, biofilm formation, adhesion and hemolysis of the <italic>znuA</italic>-RNAi, <italic>znuB</italic>-RNAi, and <italic>znuC</italic>-RNAi strains were significantly reduced. We also detected the expression of <italic>znuABC</italic> under different growth periods, temperatures, pH, as well as Cu<sup>2+</sup> and Pb<sup>2+</sup> stresses. The results showed that <italic>znuABC</italic> was significantly up-regulated in the logarithmic phase and the decline phase of <italic>A. salmonicida</italic>. Interestingly, the trend of expression levels of the <italic>znuABC</italic> at 18, 28, and 37°C was reversed to another Zn<sup>2+</sup> uptake related gene <italic>zupT</italic>. Taken together, these indicated that the <italic>znuABC</italic> was necessary for <italic>A. salmonicida</italic> SRW-OG1 pathogenicity and environmental adaptability, and was cross regulated by iron starvation, but it was not irreplaceable for <italic>A. salmonicida</italic> SRW-OG1 Zn<sup>2+</sup> uptake in the host.</p>