Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Microbial and Molecular Systems (M(2)S), Faculty of Bioscience Engineering, KU Leuven, Kasteelpark Arenberg 22, Leuven B-3001, Belgium.
Int J Food Microbiol. 2013 Aug 16;166(1):65-71. doi: 10.1016/j.ijfoodmicro.2013.06.020. Epub 2013 Jun 20.
Application of high hydrostatic pressure (HHP) constitutes a valuable non-thermal pasteurization process in modern food conservation. Triggered by our interest in the rapid adaptive evolution towards HHP resistance in the food-borne pathogen E. coli O157:H7 (strain ATCC 43888) that was demonstrated earlier, we used genetic screening to identify specific loci in which a loss-of-function mutation would be sufficient to markedly increase HHP survival. As such, individual loss of RssB (anti RpoS-factor), CRP (catabolite response protein) and CyaA (adenylate cyclase) were each found to confer significant HHP resistance in the 300MPa range (i.e. >1,000-fold), and this phenotype invariably coincided with increased resistance against heat as well. In contrast to loss of RssB, however, loss of CRP or CyaA also conferred significantly increased resistance to 600MPa (i.e. >10,000-fold), suggesting cAMP/CRP homeostasis to affect extreme HHP resistance independently of increased RpoS activity. Surprisingly, none of the rapidly emerging HHP-resistant mutants of ATCC 43888 that were isolated previously did incur any mutations in rssB, crp or cyaA, indicating that a number of other loci can guide the rapid emergence of HHP resistance in E. coli O157:H7 as well. The inability of spontaneous rssB, crp or cyaA mutants to emerge during selective enrichment under HHP selection likely stems from their decreased competitive fitness during growth. Overall, this study is the first to shed light on the possible genetic strategies supporting the acquisition of HHP resistance in E. coli O157:H7.
高静压（HHP）的应用构成了现代食品保鲜中一种有价值的非热巴氏杀菌过程。我们之前对食源性病原菌大肠杆菌 O157:H7（菌株 ATCC 43888）对 HHP 抗性的快速适应性进化产生了兴趣，由此引发了我们的研究兴趣，我们利用遗传筛选来确定特定的基因座，在这些基因座中，功能丧失突变足以显著提高 HHP 的存活率。因此，RssB（抗 RpoS 因子）、CRP（分解代谢物响应蛋白）和 CyaA（腺苷酸环化酶）的单个缺失分别被发现赋予了 300MPa 范围内（即 >1000 倍）的显著 HHP 抗性，并且这种表型总是与对热的抗性增加相一致。与 RssB 的缺失相反，然而，CRP 或 CyaA 的缺失也赋予了对 600MPa（即 >10000 倍）的显著增加的抗性，这表明 cAMP/CRP 稳态独立于 RpoS 活性的增加而影响极端 HHP 抗性。令人惊讶的是，之前从 ATCC 43888 中分离出来的对 HHP 具有快速抗性的突变体中没有任何突变发生在 rssB、crp 或 cyaA 中，这表明许多其他基因座也可以指导大肠杆菌 O157:H7 中 HHP 抗性的快速出现。在 HHP 选择下进行选择性富集时，自发的 rssB、crp 或 cyaA 突变体无法出现，这可能是由于它们在生长过程中竞争适应性降低所致。总的来说，这项研究首次揭示了可能支持大肠杆菌 O157:H7 获得 HHP 抗性的遗传策略。
