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

Jiajia Wang; Lijun Xiu; Ying Qiao; Youyu Zhang

doi:10.3389/fvets.2023.1172123

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

Front Vet Sci. 2023 Mar 29:10:1172123. doi: 10.3389/fvets.2023.1172123. eCollection 2023.

Authors

Jiajia Wang¹, Lijun Xiu¹, Ying Qiao², Youyu Zhang³

Affiliations

¹ Fisheries College, Key Laboratory of Healthy Mariculture for the East China Sea, Ministry of Agriculture, Jimei University, Xiamen, Fujian, China.
² Fourth Institute of Oceanography, Key Laboratory of Tropical Marine Ecosystem and Bioresource, Ministry of Natural Resources, Beihai, China.
³ Institute of Electromagnetics and Acoustics, School of Electronic Science and Engineering, Xiamen University, Xiamen, China.

Abstract

Psychrophilic Aeromonas salmonicida could not grow above 25°C and therefore thought unable to infect mammals and humans. In our previous study, a mesophilic A. salmonicida SRW-OG1 was isolated from Epinephelus coioides with furunculosis. Through the analysis of preliminary RNA-seq, it was found that the Zn²⁺ uptake related genes znuA, znuB and znuC might be involved in the virulence regulation of A. salmonicida SRW-OG1. Therefore, the purpose of this study was to explore the effect of znuABC silencing on the virulence regulation of A. salmonicida SRW-OG1. The results showed that the growth of the znuA-RNAi, znuB-RNAi, and znuC-RNAi strains was severely restricted under the Fe²⁺ starvation, but surprisingly there was no significant difference under the Zn²⁺ restriction. In the absence of Zn²⁺ and Fe²⁺, the expression level of znuABC was significantly increased. The motility, biofilm formation, adhesion and hemolysis of the znuA-RNAi, znuB-RNAi, and znuC-RNAi strains were significantly reduced. We also detected the expression of znuABC under different growth periods, temperatures, pH, as well as Cu²⁺ and Pb²⁺ stresses. The results showed that znuABC was significantly up-regulated in the logarithmic phase and the decline phase of A. salmonicida. Interestingly, the trend of expression levels of the znuABC at 18, 28, and 37°C was reversed to another Zn²⁺ uptake related gene zupT. Taken together, these indicated that the znuABC was necessary for A. salmonicida SRW-OG1 pathogenicity and environmental adaptability, and was cross regulated by iron starvation, but it was not irreplaceable for A. salmonicida SRW-OG1 Zn²⁺ uptake in the host.

Keywords: Aeromonas salmonicida; Epinephelus coioides; virulence regulation; zinc; znuABC.

Grants and funding

This research was funded by the Project of Subsidy Funds for Marine Economic Development in Fujian Province under grant FJHJF-L-2022-20, the major program of Science and Technology Planning of Xiamen under contract No. 3502Z20211004, and the Natural Science Foundation of Fujian Province (Nos. 2019J01695 and 2021J01823).