北京大学定量生物学中心

学术报告

报告人： 王忆平 教授

北京大学生命科学学院

题 目： Deciphering the Principles of Bacterial Nitrogen Dietary Preferences: a Strategy for Nutrient Containment

时 间：2016-9-28（周三），13:00-14:00

地 点：北京大学老化学楼东配楼一层101会议室

主持人：汤超 教授

ABSTRACT：

A fundamental question in microbial physiology concerns why organisms prefer certain nutrients to others. For example, among different nitrogen sources, ammonium is the preferred nitrogen source, supporting fast growth, whereas alternative nitrogen sources, such as certain amino acids, are considered to be poor nitrogen sources, supporting much slower exponential growth. However, the physiological/regulatory logic behind such nitrogen dietary choices remains elusive. In this study, by engineering Escherichia coli, we switched the dietary preferences toward amino acids, with growth rates equivalent to that of the wild-type strain grown on ammonia. However, when the engineered strain was cultured together with wild-type E. coli, this growth advantage was diminished as a consequence of ammonium leakage from the transport-and-catabolism (TC)-enhanced (TCE) cells, which are preferentially utilized by wild-type bacteria. Our results reveal that the nitrogen regulatory (Ntr) system fine tunes the expression of amino acid transport and catabolism components to match the flux through the ammonia assimilation pathway such that essential nutrients are retained, but, as a consequence, the fast growth rate on amino acids is sacrificed.

IMPORTANCE：

Bacteria exhibit different growth rates under various nutrient conditions. These environmentally related behaviors reflect the coordination between metabolism and the underlying regulatory networks. In the present study, we investigated the intertwined nitrogen metabolic and nitrogen regulatory systems to understand the growth differences between rich and poor nitrogen sources. Although maximal growth rate is considered to be evolutionarily advantageous for bacteria (as remarked by François Jacob, who said that the “dream” of every cell is to become two cells), we showed that negative-feedback loops in the regulatory system inhibit growth rates on amino acids. We demonstrated that in the absence of regulatory feedback, amino acids are capable of supporting fast growth rates, but this results in ammonia leaking out from cells as “waste,” benefiting the growth of competitors. These findings provide important insights into the regulatory logic that controls metabolic flux and ensures nutrient containment but consequently sacrifices growth rate.

报告人简介：

王忆平教授是北京大学生命科学学院教授，主要研究工作包括：大肠杆菌及相关细菌中的基因调控网络，尤其是碳代谢和氮代谢的调控偶联；大肠杆菌及相关细菌中的基因调控机理；植物与微生物相互作用的分子生物学及功能基因组学研究；生物修复领域的研究（功能基因的分离）；合成生物学及生物固氮；大肠杆菌定量生物学研究等。王忆平教授实验室研究成果卓著，相关工作得到国际同行的认可。详见http://www.bio.pku.edu.cn/teacher_dis_oa.php?cid=208&teaid=74