Enterohaemorrhagic Escherichia coli gains a competitive advantage by using ethanolamine as a nitrogen source in the bovine intestinal content
Enterohaemorrhagic Escherichia coli gains a competitive advantage by using ethanolamine as a nitrogen source in the bovine intestinal content
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DOI：
10.1111/j.1462-2920.2010.02334.x
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发表时间：
2011-02-01
影响因子：
5.1
通讯作者：
Martin, Christine
中科院分区：
文献类型：
--
作者：
Bertin, Yolande;Girardeau, J. P.;Martin, Christine
牛的胃肠道是引起食源性感染的肠出血性大肠杆菌(EHEC)的主要宿主。对促进反刍动物携带这些病原体的营养物质进行表征，将有助于制定生态策略，以减少它们在牛胃肠道中的存活。在这项研究中，我们首次证明了由于乙醇胺利用基因簇的诱导，游离乙醇胺(EA)构成了O157：H7 EHEC菌株EDL933牛肠道内容物中的氮源。相反，ut基因簇在组成哺乳动物肠道微生物区系的大多数物种的基因组中都缺失。此外，eutB基因(编码催化EA释放氨的酶的一个亚单位)在非致病性大肠杆菌中表达很低。因此，EA被EHEC消耗，但不能被牛小肠的内源微生物区系代谢，包括共生大肠杆菌。有趣的是，当细菌进入静止生长阶段时，利用EA作为氮源的能力为E.ColiO157：H7提供了生长优势。这些数据表明，EHEC菌株利用了不被常驻微生物区系消耗的氮源，并表明EA代表了有利于EHEC在牛肠道中持续存在的生态位。
P>The bovine gastrointestinal tract is the main reservoir for enterohaemorrhagic Escherichia coli (EHEC) responsible for food-borne infections. Characterization of nutrients that promote the carriage of these pathogens by the ruminant would help to develop ecological strategies to reduce their survival in the bovine gastrointestinal tract. In this study, we show for the first time that free ethanolamine (EA) constitutes a nitrogen source for the O157:H7 EHEC strain EDL933 in the bovine intestinal content because of induction of the eut (ethanolamine utilization) gene cluster. In contrast, the eut gene cluster is absent in the genome of most species constituting the mammalian gut microbiota. Furthermore, the eutB gene (encoding a subunit of the enzyme that catalyses the release of ammonia from EA) is poorly expressed in non-pathogenic E. coli. Accordingly, EA is consumed by EHEC but is poorly metabolized by endogenous microbiota of the bovine small intestine, including commensal E. coli. Interestingly, the capacity to utilize EA as a nitrogen source confers a growth advantage to E. coli O157:H7 when the bacteria enter the stationary growth phase. These data demonstrate that EHEC strains take advantage of a nitrogen source that is not consumed by the resident microbiota, and suggest that EA represents an ecological niche favouring EHEC persistence in the bovine intestine.