GROWTH AND COLONIZATION OF THE INTESTINE BY E COLI

为了在动物宿主中定居，细菌必须获得生长所需的营养。 然而，尽管进行了广泛的研究，但对栖息在哺乳动物大肠中的400-500种物种原位使用的营养物质和代谢途径几乎一无所知。该研究利用功能基因组学技术来研究肠道细菌在定植过程中对营养物质的获取。 具体地说，我们将检验这一假设，即诱导粘液来源的糖的催化途径是大肠杆菌定殖所必需的。杆菌全局转录测定将用于鉴定在肠粘液中存在的营养物的复杂混合物上诱导生长的调节子。 从在含有盲肠粘液的基本培养基上生长的细胞制备的探针将与所有E. coli基因。 通过分析E.大肠杆菌细胞在实验定植无菌小鼠盲肠。 这些途径有助于E.大肠杆菌成功地与大肠中的400-500种其他物种竞争将被检查。 将测试在特定分解代谢途径中选择性阻断的突变菌株在小鼠中定殖的能力，并且将使用绿色荧光蛋白报告基因融合物来确定定殖期间这些调节子在单个细菌细胞中的时间和空间表达。这些实验将确定个别粘膜糖在大肠杆菌定植中的不同生理作用。大肠杆菌，为解决代谢多样性是否允许致病性大肠杆菌的更普遍的问题提供重要的知识。大肠杆菌菌株在预先定殖的菌株存在的情况下定殖，从而导致它们致病的能力。 准确地了解哪些营养素是定植所必需的，应该有助于改善对抗感染的策略。

To colonize an animal host, bacteria must acquire nutrients for growth. However, despite extensive research, next to nothing is known about the nutrients and metabolic pathways used in situ by the 400-500 species which inhabit the mammalian large intestine. The proposed research uses functional genomics technology to investigate the acquisition of nutrients by enteric bacteria during the colonization process. Specifically, we will test the hypothesis that induction of the pathways used for catabolism of mucus-derived sugars is essential for colonization of E. coli. Global transcription assays will be used to identify regulons induced for growth on the complex mixture of nutrients present in intestinal mucus. Probes prepared from cells grown on minimal media containing cecal mucus will be hybridized to DNA arrays of all E. coli genes. Pathways induced in situ for growth on mucus will be identified by analyzing global transcription patterns of E. coli cells in the ceca of experimentally colonized germ-free mice. Pathways which contribute to the ability of E. coli to successfully compete with the 400-500 other species in the large intestine will be examined. Mutant strains selectively blocked in specific catabolic pathways will be tested for their ability to colonize mice and green fluorescent protein reporter fusions will be used to determine the temporal and spatial expression of these regulons in individual bacterial cells during colonization. These experiments will identify the distinct physiological roles of individual mucosal sugars in colonization of the large intestine by E. coli, providing knowledge important for addressing the more general question of whether or not metabolic diversity allows pathogenic E. coli strains to colonize in the presence of precolonized strains, thus leading to their ability to cause disease. Knowing precisely which nutrients are essential for colonization should lead to improved strategies for combating infection.