Food Microbiology, Wageningen University and Research, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
National Institute of Public Health and the Environment P.O. Box 1, 3720 BA Bilthoven, The Netherlands.
Int J Food Microbiol. 2018 Oct 20;283:14-21. doi: 10.1016/j.ijfoodmicro.2018.06.003. Epub 2018 Jun 7.
Microbial population heterogeneity allows for a differential microbial response to environmental stresses and can lead to the selection of stress resistant variants. In this study, we have used two different stress resistant variants of Listeria monocytogenes LO28 with mutations in the rpsU gene encoding ribosomal protein S21, to elucidate features that can contribute to fitness, stress-tolerance and host interaction using a comparative gene profiling and phenotyping approach. Transcriptome analysis showed that 116 genes were upregulated and 114 genes were downregulated in both rpsU variants. Upregulated genes included a major contribution of SigB-controlled genes such as intracellular acid resistance-associated glutamate decarboxylase (GAD) (gad3), genes involved in compatible solute uptake (opuC), glycerol metabolism (glpF, glpK, glpD), and virulence (inlA, inlB). Downregulated genes in the two variants involved mainly genes involved in flagella synthesis and motility. Phenotyping results of the two rpsU variants matched the gene profiling data including enhanced freezing resistance conceivably linked to compatible solute accumulation, higher glycerol utilisation rates, and better adhesion to Caco 2 cells presumably linked to higher expression of internalins. Also, bright field and electron microscopy analysis confirmed reduced flagellation of the variants. The activation of SigB-mediated stress defence offers an explanation for the multiple-stress resistant phenotype in rpsU variants.
微生物种群异质性允许微生物对环境压力产生不同的反应，并可能导致选择具有抗压力的变体。在这项研究中，我们使用了两种不同的抗压力李斯特菌变异体 LO28，它们在编码核糖体蛋白 S21 的 rpsU 基因中有突变，使用比较基因谱和表型分析方法来阐明有助于适应性、抗应激性和宿主相互作用的特征。转录组分析表明，两个 rpsU 变异体中有 116 个基因上调，114 个基因下调。上调的基因包括 SigB 控制的基因的主要贡献，如细胞内酸抗性相关的谷氨酸脱羧酶 (GAD) (gad3)、参与相容溶质摄取的基因 (opuC)、甘油代谢 (glpF、glpK、glpD) 和毒力 (inlA、inlB)。两个变异体中下调的基因主要涉及鞭毛合成和运动的基因。两种 rpsU 变异体的表型结果与基因谱数据相匹配，包括增强的抗冻性，这可能与相容溶质的积累有关，更高的甘油利用率，以及更好的粘附到 Caco 2 细胞，这可能与内部素的更高表达有关。此外，明场和电子显微镜分析证实了这些变体的鞭毛减少。SigB 介导的应激防御的激活为 rpsU 变体的多应激抗性表型提供了一个解释。
