The two-component system expression patterns and immune regulatory mechanism of Vibrio parahaemolyticus with different genotypes at the early stage of infection in THP-1 cells.

Vibrio parahaemolyticus must endure various challenging circumstances while being swallowed by phagocytes of the innate immune system. Moreover, bacteria should recognize and react to environmental signals quickly in host cells. Two-component system (TCS) is an important way for bacteria to perceive external environmental signals and transmit them to the interior to trigger the associated regulatory mechanism. However, the regulatory function of V. parahaemolyticus TCS in innate immune cells is unclear. Here, the expression patterns of TCS in V. parahaemolyticus-infected THP-1 cell-derived macrophages at the early stage were studied for the first time. Based on protein-protein interaction network analysis, we mined and analyzed seven critical TCS genes with excellent research value in the V. parahaemolyticus regulating macrophages, as shown below. VP1503, VP1502, VPA0021, and VPA0182 could regulate the ATP-binding-cassette (ABC) transport system. VP1735, uvrY, and peuR might interact with thermostable hemolysin proteins, DNA cleavage-related proteins, and TonB-dependent siderophore enterobactin receptor, respectively, which may assist V. parahaemolyticus in infected macrophages. Subsequently, the potential immune escape pathways of V. parahaemolyticus regulating macrophages were explored by RNA-seq. The results showed that V. parahaemolyticus might infect macrophages by controlling apoptosis, actin cytoskeleton, and cytokines. In addition, we found that the TCS (peuS/R) could enhance the toxicity of V. parahaemolyticus to macrophages and might contribute to the activation of macrophage apoptosis. IMPORTANCE This study could offer crucial new insights into the pathogenicity of V. parahaemolyticus without tdh and trh genes. In addition, we also provided a novel direction of inquiry into the pathogenic mechanism of V. parahaemolyticus and suggested several TCS key genes that may assist V. parahaemolyticus in innate immune regulation and interaction.

Effect of low temperature on the resistance of Listeria monocytogenes and Escherichia coli O157:H7 to acid electrolyzed water.

Low temperature can affect the resistance of pathogenic bacteria to other external stress. The present study was envisaged to assess the tolerance of L. monocytogenes and E. coli O157:H7 to acidic electrolyzed water (AEW) under low temperature stress. AEW treatment caused a damage to cell membrane of the pathogenic bacteria, which led to protein leakage and DNA damage. Compared with the pathogenic bacteria cultured at 37 °C (pure culture), the L. monocytogenes and E. coli O157:H7 cells cultivated at low temperature presented a less damage and had a higher survival rate when exposed to AEW. Therefore, 4 °C or 10 °C grown bacteria were less susceptible to AEW than those cultured at 37 °C. And this phenomenon was verified when AEW was used to treat the pathogenic bacteria inoculated in salmon. In addition, transcriptomic sequencing technology (RNA-seq) was used to reveal the mechanism of AEW tolerance of L. monocytogenes under low temperature stress. Transcriptomic analysis showed the expression of the cold shock protein, regulation of DNA-templated transcription, ribosome pathway, phosphotransferase system (PTS), bacteria chemotaxis, SOS response and DNA repair were involved in the resistance of L. monocytogenes to AEW. We speculated that the direct modulation of the expression of cold shock protein CspD, the indirect effect on the expression of cspD by inhibiting the expression of Crp/Fnr family transcriptional regulator or enhancing the level of cAMP by regulating PTS could reduce the resistance of L. monocytogenes cultivated at 4 °C to AEW. Our study contributes to solving the problem of the reduced bacteriostatic effect in cold storage environment.