Abstract: 【Objective】 This study was conducted to clarify the roles of two-component system LisRK of Listeria monocytogenes in stress resistance and infection.【Method】 The deletion strain ΔlisRK was constructed by homologous recombination with shuttle vector pKSV7 at the background of wild type strain 10403S and the complemental strain CΔlisRK was constructed with plasmid pIMK2.The growth and survival ability of the strains 10403S, ΔlisRK and CΔlisRK under various stresses including acidic (pH 4.5), osmotic (5% NaCl) and oxidative (10 mmol/L H₂O₂) conditions were analyzed.Then the invasion rate to MGC803 cells and Caco-2 cells, and bacteria load in the liver and spleen of infected mice of strains 10403S, ΔlisRK and CΔlisRK were compared.【Result】 The results of stress test showed that the deletion strain ΔlisRK significantly reduced the growth ability of Listeria monocytogenes under acid stress (pH 4.5), but did not affect the growth ability of Listeria monocytogenes in 5% NaCl and 10 mmol/L H₂O₂.The survival rate (0.57%) of the deletion strain ΔlisRK under severe acid stress (pH 2.5) was extremely significantly lower than that of strains 10403S (2.07%) and CΔlisRK (1.97%) (P < 0.01).Cell invasion test showed that the invasion rates of the deletion strain ΔlisRK on intestinal epithelial cell Caco-2 and gastric adenocarcinoma cell MGC803 were 2.04% and 0.13%, respectively, which were extremely significantly or significantly lower than that of strains 10403S and CΔlisRK (P < 0.01;P < 0.05).The mouse infection test showed that bacteria load in the liver and spleen of ΔlisRK infected mice were 7.42×10⁷and 1.87×10⁷CFU, which were lower than those of 10403S and CΔlisRK, respectively, but there were no significant difference (P > 0.05).【Conclusion】 These data demonstrated that knocking out the LisRK impaired the acid resistance and invasiveness of Listeria monocytogenes.

Key words: Listeria monocytogenes; two-component system; acid resistance; invasiveness