Microbial genome sequencing projects are beginning to provide insights about the molecular foundations of human-bacterial symbioses. The intestine contains our largest collection of symbionts, where members of Bacteroides comprise approximately 25% of the microbiota in adults. The recently defined proteome of a prominent human intestinal symbiont, Bacteroides thetaiotaomicron, contains an elaborate environmental-sensing apparatus. This apparatus includes an unprecedented number of extracytoplasmic function (ECF) sigma-factors, and a large collection of novel hybrid two-component systems composed of membrane-spanning periplasmic proteins with histidine kinase, phosphoacceptor, response regulator receiver and DNA-binding domains. These sensors are linked to the organism's large repertoire of genes involved in acquiring and processing dietary polysaccharides ('the glycobiome'). This arrangement illustrates how a successful symbiont has evolved strategies for detecting and responding to conditions in its niche so that it can sustain beneficial relationships with its microbial and human partners.

中文翻译：

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来自人类肠道共生体的信息：敏感性是共享的前提。

微生物基因组测序项目开始提供有关人类细菌共生酶分子基础的见识。肠道中含有我们最多的共生菌，其中拟杆菌属的成员约占成年人微生物群的25％。最近定义的一种突出的人类肠道共生体蛋白质组细菌拟杆菌（Bacteroides thetaiotaomicron）包含一种精心设计的环境传感装置。该设备包括空前数量的胞浆外功能（ECF）σ因子，以及大量新的杂合二组分系统，这些系统由跨膜的周质蛋白与组氨酸激酶，磷酸受体，响应调节受体和DNA结合域组成。这些传感器与生物体的 涉及获取和加工膳食多糖（“糖生物组”）的大量基因。这种安排说明了成功的共生体如何发展出检测和响应其利基条件的策略，从而使其能够维持与其微生物和人类伙伴的有益关系。