Department of Microbiology and Immunology, McGill University, Montreal, QC, Canada.
Gut Microbes. 2012 Nov-Dec;3(6):556-61. doi: 10.4161/gmic.21656. Epub 2012 Aug 16.
Enterohemorrhagic and enteropathogenic Escherichia coli (EHEC and EPEC) are enteric human pathogens that colonize the large and small intestines, respectively. To establish infection EHEC and EPEC must overcome innate host defenses, such as antimicrobial peptides (AMPs) produced by the intestinal epithelium. Gram-negative pathogens have evolved different mechanisms to resist AMPs, including outer-membrane proteases that degrade AMPs. We showed that the protease OmpT degrades the human AMP LL-37 more rapidly in EHEC than in EPEC. Promoter-swap experiments showed that this is due to differences in the promoters of the two genes, leading to greater ompT expression and subsequently greater levels of OmpT in EHEC. Here, we propose that the different ompT expression in EHEC and EPEC reflects the varying levels of LL-37 throughout the human intestinal tract. These data suggest that EHEC and EPEC adapted to their specific niches by developing distinct AMP-specific resistance mechanisms.
肠出血性和肠致病性大肠杆菌（EHEC 和 EPEC）分别是定植于大肠和小肠的肠道人类病原体。为了建立感染，EHEC 和 EPEC 必须克服先天的宿主防御，例如由肠道上皮细胞产生的抗菌肽（AMPs）。革兰氏阴性病原体已经进化出不同的机制来抵抗 AMPs，包括降解 AMPs 的外膜蛋白酶。我们表明，蛋白酶 OmpT 在 EHEC 中比在 EPEC 中更快地降解人类 AMP LL-37。启动子交换实验表明，这是由于两个基因的启动子存在差异，导致 EHEC 中 ompT 的表达更高，随后 OmpT 的水平更高。在这里，我们提出 EHEC 和 EPEC 中不同的 ompT 表达反映了人类肠道中 LL-37 的不同水平。这些数据表明，EHEC 和 EPEC 通过开发独特的 AMP 特异性抗性机制来适应其特定的生态位。
