Effects of low-salt stress on biological characteristics and transcriptomic profiles of Vibrio parahaemolyticus

Studies have proved that halophilic Vibrio parahaemolyticus is widely detected in freshwater environments (salinity <0.5 %). However, the growth and colonization of V. parahaemolyticus in low-salt environments remain unclear. This study was envisaged to assess the effects of low-salt stress on the growth, motility and biofilm formation of V. parahaemolyticus and the transcriptomic changes that the bacterium responds to such stress. The results indicated that low salt concentrations supported the growth (allowing growth to proceed, though at a lower speed) of V. parahaemolyticus, prolonged the lag time (LT), and decreased the maximum specific growth rate (μ_max) of V. parahaemolyticus. Additionally, this low salinity inhibited its motility and enhanced its biofilm formation capacity. Notably, the growth of V. parahaemolyticus on both freshwater and marine-cultured Litopenaeus vannamei exhibited a similar trend, suggesting that V. parahaemolyticus might have adapted to thrive in freshwater food. Furthermore, the reasons for the support of V. parahaemolyticus growth in 0.25 % NaCl was analyzed by transcriptome sequencing (RNA-seq). RNA-seq revealed that V. parahaemolyticus can improve resistance to adverse environments by reducing energy consumption and enhancing oxidative stress resistance to adapt to a low-salt environment. This study revealed that the freshwater environment supported the growth of V. parahaemolyticus and its influence on the growth of V. parahaemolyticus, providing valuable theoretical support for risk assessment.