Enhanced Hemolytic Activity of Mesophilic Aeromonas salmonicida SRW-OG1 Is Brought about by Elevated Temperatures

Yunong Chen; Jiajia Wang; Hongyan Cai; Mao Lin; Youyu Zhang; Lixing Huang

doi:10.3390/microorganisms10102033

Enhanced Hemolytic Activity of Mesophilic Aeromonas salmonicida SRW-OG1 Is Brought about by Elevated Temperatures

Microorganisms. 2022 Oct 14;10(10):2033. doi: 10.3390/microorganisms10102033.

Authors

Yunong Chen¹, Jiajia Wang¹, Hongyan Cai¹, Mao Lin¹, Youyu Zhang², Lixing Huang¹

Affiliations

¹ Key Laboratory of Healthy Mariculture for the East China Sea, Fisheries College, Jimei University, Ministry of Agriculture, Xiamen 361000, China.
² Institute of Electromagnetics and Acoustics, School of Electronic Science and Engineering, Xiamen University, Xiamen 361000, China.

Abstract

Aeromonas salmonicida is a well-known cold-water pathogenic bacterium. Previously, we reported the first isolation of pathogenic A. salmonicida from diseased Epinephelus coioides, a kind of warm-water fish, and it was proved to be a putative mesophilic strain with potent pathogenicity to humans. In order to investigate the mechanisms underlying mesophilic growth ability and virulence, the transcriptome of A. salmonicida SRW-OG1 at 18, 28, and 37 °C was analyzed. The transcriptome of A. salmonicida SRW-OG1 at different temperatures showed a clear separation boundary, which might provide valuable information for the temperature adaptation and virulence regulation of A. salmonicida SRW-OG1. Interestingly, aerA and hlyA, the hemolytic genes encoding aerolysin and hemolysin, were found to be significantly up-regulated at 28 and 37 °C. Since aerolysin and hemolysin are the most well-known and -characterized virulence factors of pathogenic Aeromonas strains, the induction of aerA and hlyA was associated with the mesophilic virulence. Further study proved that the extracellular products (ECPs) purchased from A. salmonicida SRW-OG1 cultured at 28 and 37 °C showed elevated hemolytic activity and virulence than those at 18 °C. Moreover, the silence of aerA and hlyA led to significantly decreased hemolysis and virulence. Taken together, our results revealed that the mesophilic virulence of A. salmonicida SRW-OG1 might be due to the enhanced expression of aerA and hlyA induced by elevated temperatures.

Keywords: Aeromonas salmonicida; aerA; hlyA; temperature adaption; transcriptome analysis; virulence regulation.

Grants and funding

This research was funded by the major program of Science and Technology Planning of Xiamen under Contract No. 3502Z20211004, the Fujian Engineering Research Center of Aquatic Breeding and Healthy Aquaculture, under Contract No. DF201903, and the Natural Science Foundation of Fujian Province (No. 2019J01695 and 2021J01823).