Genome-wide transcriptional profiling of the cell envelope stress response and the role of LisRK and CesRK in Listeria monocytogenes

The Gram-positive bacterium Listeria monocytogenes is widely distributed in the environment and capable of causing food-borne infections in susceptible individuals. In this study, we investigated the cell envelope stress response in L. monocytogenes. Whole-genome transcriptional profiling was performed to investigate the response upon exposure to the cell wall antibiotic cefuroxime. Differential expression (at least twofold) of 558 genes was observed, corresponding to 20% of the L. monocytogenes genome. The majority of genes that were strongly induced by cefuroxime exposure have cell-envelope-related functions, including the dlt operon and the gene encoding penicillin-binding protein PBPD2. A large overlap was observed between the cefuroxime stimulon and genes known to be induced in L. monocytogenes in blood and during intracellular infection, indicating that the cell envelope stress response is active at various stages of the infectious process. We analysed the roles of the two-component systems LisRK and CesRK in the cell envelope response, showing that activation of the most highly cefuroxime-induced genes was LisR- and CesR-dependent. In addition, multiple VirRS- and LiaSR-regulated genes were found to be induced in response to cefuroxime exposure. In total, 53% of the genes upregulated at least fourfold by cefuroxime exposure are under positive control by one of the four two-component systems. Using genetic analyses, we showed that several genes of the cefuroxime stimulon contribute to the innate resistance of L. monocytogenes to cefuroxime and tolerance to other cell-envelope-perturbing conditions. Collectively, these findings demonstrate central roles for two-component systems in orchestrating the cell envelope stress response in L. monocytogenes.