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

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.

Effect of the zinc transporter ZupT on the virulence mechanisms of mesophilic Aeromonas salmonicida SRW‐OG1

“…Aeromonas salmonicida, a Gram-negative bacterial pathogen, is primarily associated with furunculosis in cold-water bony fish, including Salmonidae and Cyprinidae species [1][2][3][4][5]. Traditionally, A. salmonicida has been considered incapable of growth above 25°C and, therefore, has not been implicated in mammalian or human diseases [1][2][3][4][5][6][7][8][9][10].…”

“…Aeromonas salmonicida, a Gram-negative bacterial pathogen, is primarily associated with furunculosis in cold-water bony fish, including Salmonidae and Cyprinidae species [1][2][3][4][5]. Traditionally, A. salmonicida has been considered incapable of growth above 25°C and, therefore, has not been implicated in mammalian or human diseases [1][2][3][4][5][6][7][8][9][10]. The orange-spotted grouper (Epinephelus coioides), widely distributed in tropical and subtropical regions, is among the most extensively cultured Epinephelus species along the coastal areas of China, such as Fujian, Guangdong, and Hainan [11][12][13][14][15].…”

“…Transition metal elements, such as iron (Fe) and zinc (Zn), are highly demanded by living organisms [1,[19][20][21]. In prokaryotes, approximately 10% of proteins require zinc for their formation, including zinc-binding proteins [1,[22][23][24].…”

“…Transition metal elements, such as iron (Fe) and zinc (Zn), are highly demanded by living organisms [1,[19][20][21]. In prokaryotes, approximately 10% of proteins require zinc for their formation, including zinc-binding proteins [1,[22][23][24]. Interestingly, in certain bacterial pathogens, high concentrations of zinc can be lethal, thus a deficiency in the zinc transport system may lead to reduced pathogenicity [25][26][27].…”

“…Interestingly, in certain bacterial pathogens, high concentrations of zinc can be lethal, thus a deficiency in the zinc transport system may lead to reduced pathogenicity [25][26][27]. Two zinc transport systems have been identified in bacteria [1,28]. The first is analogous to Escherichia coli's ZnuABC, a highaffinity zinc transport system [1,27], which is the most widely distributed among bacterial species [1,29].…”