KU Leuven, Laboratory of Food Microbiology, Department of Microbial and Molecular Systems (M2S), Faculty of Bioscience Engineering, Leuven, Belgium.
Sci Rep. 2017 Aug 17;7(1):8600. doi: 10.1038/s41598-017-08958-z.
High hydrostatic pressure (HHP) processing is an attractive non-thermal alternative to food pasteurization. Nevertheless, the large inter- and intra-species variations in HHP resistance among foodborne pathogens and the ease by which they can acquire extreme resistance are an issue of increasing concern. Since RpoS activity has been considered as a central determinant in the HHP resistance of E. coli and its pathovars, this study probed for the potential of an E. coli MG1655 ΔrpoS mutant to acquire HHP resistance by directed evolution. Despite the higher initial HHP sensitivity of the ΔrpoS mutant compared to the wild-type strain, evolved lineages of the former readily managed to restore or even succeed wild-type levels of resistance. A number of these ΔrpoS derivatives were affected in cAMP/CRP regulation, and this could be causally related to their HHP resistance. Subsequent inspection revealed that some of previously isolated HHP-resistant mutants derived from the wild-type strain also incurred a causal decrease in cAMP/CRP regulation. cAMP/CRP attenuated HHP-resistant mutants also exhibited higher resistance to fosfomycin, a preferred treatment for STEC infections. As such, this study reveals attenuation of cAMP/CRP regulation as a relevant and RpoS-independent evolutionary route towards HHP resistance in E. coli that coincides with fosfomycin resistance.
高静压（HHP）处理是一种有吸引力的非热食品巴氏杀菌替代方法。然而，食源性病原体之间以及它们之间 HHP 抗性的巨大种间和种内变异，以及它们很容易获得极端抗性，这是一个日益令人关注的问题。由于 RpoS 活性被认为是大肠杆菌及其病原菌 HHP 抗性的一个重要决定因素，因此本研究通过定向进化探究了大肠杆菌 MG1655 ΔrpoS 突变体获得 HHP 抗性的潜力。尽管与野生型菌株相比，ΔrpoS 突变体的初始 HHP 敏感性更高，但前者的进化谱系很容易恢复甚至超过野生型水平的抗性。这些 ΔrpoS 衍生株中的许多在 cAMP/CRP 调节方面受到影响，这可能与其 HHP 抗性有关。随后的检查表明，一些先前从野生型菌株中分离出来的耐 HHP 突变体也导致 cAMP/CRP 调节的因果减少。cAMP/CRP 减弱的耐 HHP 突变体也表现出对福司福霉素更高的抗性，福司福霉素是治疗 STEC 感染的首选药物。因此，本研究揭示了 cAMP/CRP 调节的衰减是大肠杆菌中与 fosfomycin 抗性相关的、与 RpoS 无关的 HHP 抗性的一个相关和独立的进化途径。
