Effects of luxS on environmental adaptability of Listeria monocytogenes

Abstract:

Objective To investigate the effects of luxS deletion on the biofilm formation and stress tolerance of Listeria monocytogenes and to elucidate the role of luxS in regulating environmental adaptability of this pathogen.Methods With Listeria monocytogenes ATCC 19112 as the parental strain, a luxS-deleted mutant, a complemented strain, and an empty-vector control strain were constructed. Growth curve analysis, environmental stress tolerance assays and biofilm formation assays were performed to comparatively analyze phenotypic differences among the wild-type, mutant, and complemented strains.Results Compared with the wild-type strain, the luxS-deleted mutant exhibited reduced adaptability under adverse conditions, including low temperature, high osmotic pressure, oxidative stress, and acid stress. Its biofilm-forming ability decreased after 24 h and 48 h of incubation (P<0.01), accompanied by a reduction in the production of extracellular polymeric substances in the biofilm matrix. Further transcriptional analysis revealed that the expression levels of agrA, agrB, lmo2504, and sigB were downregulated (P<0.05), whereas that of ladR was upregulated (P<0.05) following luxS deletion. Under disinfectant stress, MTT assay showed that the metabolic activity of the luxS-deleted strain was lower than that of the wild-type and complemented strains after 48 h of biofilm cultivation (P<0.05). After 72 h, no significant differences were observed among the strains.Conclusion These findings demonstrate that luxS plays a critical role in regulating the environmental adaptability of L. monocytogenes and provide a novel theoretical basis for the development of future control and prevention strategies targeting this pathogen.