Ethanolamine Utilization Contributes to Proliferation of Salmonella enterica Serovar Typhimurium in Food and in Nematodes
Ethanolamine Utilization Contributes to Proliferation of Salmonella enterica Serovar Typhimurium in Food and in Nematodes
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DOI：
10.1128/aem.01403-10
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发表时间：
2010-10
影响因子：
4.4
通讯作者：
S. Srikumar;T. Fuchs
中科院分区：
文献类型：
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作者：
S. Srikumar;T. Fuchs
摘要：只有三种致病菌，即肠沙门氏菌、产气荚膜梭菌和单核细胞增生李斯特氏菌，能够利用乙醇胺和 1,2-丙二醇作为唯一碳源。这些在食物和肠道中丰富的底物的降解取决于钴胺素，钴胺素仅在厌氧条件下从头合成。尽管 eut、pdu 和 cob-cbi 基因簇包含 40 kb，但它们赋予这些食源性病原体选择优势的条件仍然很大程度上未知。在这里，我们使用荧光素酶报告系统来确定肠沙门氏菌鼠伤寒血清型启动子 P eutS 、 P pocR 、 P pduF 和 P pduA 对一组碳源、蛋黄、全脂牛奶和牛奶蛋白或脂肪组分的反应。根据补充剂的不同，观察到 P eutS 和 P pduA 的特异性诱导高达 3 个数量级，它们驱动大多数 eut 和 pdu 基因的表达。为了将这些重要的表达数据与生长特性相关联，在鼠伤寒沙门氏菌菌株14028中构建了调节pdu和cob-cbi基因的pocR以及参与eut基因激活的eutR的非极性删除。在突变体14028ΔpocR和14028ΔeutR的指数生长过程中，牛奶和蛋黄中的增殖减少了2至3倍 观察到。使用秀丽隐杆线虫感染模型，我们还可以证明鼠伤寒沙门氏菌在线虫中的增殖是由活跃的乙醇胺降解途径支持的。综合这些发现，本研究量化了 eut 和 pdu 基因在不同条件下的差异表达，并提供了实验证据，证明乙醇胺利用途径使沙门氏菌能够在食品环境及其宿主生物体内占据特定的代谢生态位。
ABSTRACT Only three pathogenic bacterial species, Salmonella enterica, Clostridium perfringens, and Listeria monocytogenes, are able to utilize both ethanolamine and 1,2-propanediol as a sole carbon source. Degradation of these substrates, abundant in food and the gut, depends on cobalamin, which is synthesized de novo only under anaerobic conditions. Although the eut, pdu, and cob-cbi gene clusters comprise 40 kb, the conditions under which they confer a selection advantage on these food-borne pathogens remain largely unknown. Here we used the luciferase reporter system to determine the response of the Salmonella enterica serovar Typhimurium promoters P eutS , P pocR , P pduF , and P pduA to a set of carbon sources, to egg yolk, to whole milk, and to milk protein or fat fractions. Depending on the supplements, specific inductions up to 3 orders of magnitude were observed for P eutS and P pduA , which drive the expression of most eut and pdu genes. To correlate these significant expression data with growth properties, nonpolar deletions of pocR, regulating the pdu and cob-cbi genes, and of eutR, involved in eut gene activation, were constructed in S. Typhimurium strain 14028. During exponential growth of the mutants 14028ΔpocR and 14028ΔeutR, 2- to 3-fold-reduced proliferation in milk and egg yolk was observed. Using the Caenorhabditis elegans infection model, we could also demonstrate that the proliferation of S. Typhimurium in the nematode is supported by an active ethanolamine degradation pathway. Taking these findings together, this study quantifies the differential expression of eut and pdu genes under distinct conditions and provides experimental evidence that the ethanolamine utilization pathway allows salmonellae to occupy specific metabolic niches within food environments and within their host organisms.