Effects of Salinity Fluctuation on Antimicrobial Resistance and Virulence Factor Genes of Low and High Nucleic Acid-Content Bacteria in a Marine Environment.

Salinity, as one of the critical environmental factors in marine ecosystems, has complex and wide-ranging biological effects. However, the effects of salinity fluctuation on antibiotic resistance genes (ARGs) and virulence factor genes (VFGs) in the marine environment are not well understood. In this study, metagenomic sequencing analysis was used to reveal the response of ARGs and VFGs, hosted by low and high nucleic acid-content bacteria (HNA and LNA bacteria), to salinity, as it decreased from 26‱ to 16‱. The results showed that a total of 27 ARG types and 13 VFG types in HNA and LNA bacteria were found. Salinity changes had significant effects on the ARGs' and VFGs' composition and their hosts' composition. In the network topology relationship, the complexity of the network between the ARGs and their host as well as the VFGs and their host differed with the decrease in salinity. The abundance of most genera of HNA and LNA bacteria was significantly corrected with the abundance of ARGs and VFGs, respectively. Overall, this study demonstrates the effects of salinity on ARGs and VFGs hosted by HNA and LNA bacteria in the marine environment and suggests the importance of salinity in regulating HNA and LNA bacterial communities and functions.