单核细胞增生李斯特菌luxS基因对该菌环境适应性的影响

Effects of luxS on environmental adaptability of Listeria monocytogenes

摘要:

目的 研究单核细胞增生李斯特菌(Listeria monocytogenes, LM) luxS基因缺失对生物被膜形成及应激耐受性的影响，探讨luxS基因在单核细胞增生李斯特菌环境适应性调控中的作用。方法 以ATCC 19112为亲本株，构建luxS基因缺失株、回补株及空载对照株。通过生长曲线测定、环境适应能力和生物被膜形成能力试验对比分析标准株、缺失株与回补株的表型差异。结果 与标准株相比，luxS基因缺失株在低温、高渗透压、氧化及酸胁迫等不利条件下环境适应性显著减弱；生物被膜在培养24 h和48 h后形成能力显著降低(P<0.01)，胞外聚合物生成量也显著减少。转录水平分析结果显示，luxS缺失后agrA、agrB、lmo2504及sigB表达水平均显著下调(P<0.05)，而ladR基因表达水平显著上调(P<0.05)。在消毒剂胁迫条件下，MTT法检测结果表明luxS基因缺失株在生物被膜培养48 h后细胞代谢活性显著低于标准株和回补株(P<0.05)，而培养72 h后各菌株间差异不显著。结论 本研究表明luxS基因在调控单核细胞增生李斯特菌环境适应性中发挥重要作用，可为该病原防控策略的设计提供新的理论依据。

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.