Abstract:Objective Listeria monocytogenes (Lm) is a Gram-positive foodborne pathogen causing human and animal listeriosis with high case fatality rates (20%-30%). Lm can grow at low temperatures, which brings great risks to food safety and human health. Exploring the mechanism of Lm growth at low temperatures will provide a theoretical basis for the formulation of measures to control Lm growth at low temperatures and the development of low-temperature growth inhibitors. Studies have shown that LisK/R, a two-component signal transduction system (TCS) in Lm, plays a role in regulating the growth of Lm at low temperatures, while the specific mechanism remains unclear. This study aims to reveal the mechanism of LisK/R in regulating the growth of Lm at low temperatures. Methods With the Lm strain LM201 isolated from foodstuff as the parental strain, we constructed three strains: ΔlisR (RR-deleted mutant of LisK/R), ΔlisRc (complementary strain of ΔlisR), and ΔlisKc (complementary strain of ΔlisK, which was constructed before this study in our laboratory). The growth curves of these strains were determined at 4 ℃. RNA-Seq was performed for ΔlisK and the parental strain growing at 4 ℃, and the obtained data were analyzed. We assayed the swarming area diameter on soft agar plate, flagellar biosynthesis by transmission electron microscopy, and transcriptional levels of flagellar genes by RT-qPCR for all the strains at 4 ℃. Results The growth of deletion mutants was slower than that of the parental strain (P<0.05), and the growth of complementary strains was consistent with that of the parental strain at 4 ℃. The RNA-Seq data showed that compared with that in the parental strain, the expression of flagellar genes in ΔlisK was up-regulated (P<0.05). At 4 ℃, the swarming area diameters of deletion mutants on soft agar plates were bigger than those of the parental strain and complementary strains (P<0.05); the deletion mutants had more flagella, while the parental and complementary strains had fewer flagella; the expression of flagellar genes in the deletion mutants was higher than that in the parental and complementary strains (P<0.05). Conclusion At 4 ℃, the LisK/R mutants with slow growth had more flagella, while the parental strain with rapid growth had fewer flagella. The results indicate that LisK/R inhibits the expression of flagellar genes in Lm to reduce flagellar production, and the energy is used to promote Lm growth at low temperatures. The specific molecular regulatory mechanism of LisK/R needs further study. This study provides new information for elucidating the mechanism of Lm growth at low temperatures.