Characterization and analysis of bacterial sugar utilization strategies employing regulated phenotypic heterogeneity

利用受调控表型异质性的细菌糖利用策略的表征和分析

• 批准号: 218275476
• 负责人: Professor Dr. Ulrich Gerland
• 金额: --
• 依托单位: Lehrstuhl für Theorie komplexer Biosysteme
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2012
• 资助国家: 德国
• 起止时间: 2011-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/218275476?language=en
• 关键词: Characterization; analysis; bacterial; sugar; utilization

This project studies bacterial regulation strategies for sugar uptake systems. In these systems, phenotypic heterogeneity is not only associated with a statistical distribution of phenotypes at a given point in time, but also with a significant cell-to-cell variability in the timing of phenotype switches. Our central goals are (i) to characterize heterogeneous timing as a dynamic gene regulation strategy and (ii) to analyze phenotypic heterogeneity in competing sugar utilization systems. In the first funding period of the SPP1617, we performed a detailed experimental and theoretical analysis of the phenomenon of heterogeneous timing in the single-cell gene expression dynamics of the arabinose system of E. coli. We found that the physiological switching behavior of this sugar utilization system is asymmetric, such that OFF-switching is always rapid and homogeneous, while ON-switching is slow and heterogeneously timed at sub-saturating inducer levels. We consolidated these and mutant behaviors within a single quantitative model. Regarding (ii), we studied cell growth on two competing PTS substrates, Sorbitol and N-acetylglucosamine (Nag), in a broad range of external substrate concentrations, while quantifying the expression of the Nag and Sorbitol utilization systems on the single-cell level. Our data supports a model of a hierarchical interaction that breaks down to allow stochastic co-utilization at low concentrations of the dominant sugar (Nag). For the second period of the SPP, we plan to study possible benefits of the observed phenotypic heterogeneity in the behavior of sugar utilization systems. Our theoretical analysis predicts that heterogeneous timing can be a useful bet-hedging strategy during stationary phase: Heterogeneous timing can minimize the risk of inducing costly gene expression after sensing nutrient sources that may be transient and disappear before a cell benefits from its expression investment. To quantify the cost of gene expression during stationary phase, we will measure the effects of gratuitous gene expression from inducible promoters on fitness indicators such as viability, metabolic activity, membrane potential, and membrane integrity. We will also seek to identify the pool of energy and/or resources that limits the total gene expression capacity of stationary phase cells. The obtained data will be integrated into a quantitative cost-benefit analysis of stationary phase gene expression, which will then be the basis for an experimentally well-founded theoretical analysis of beneficial regulation strategies. The other task for the modeling component of this proposal will be the analysis of a nutrient-sensing signaling network in E. coli that is activated at the transition to stationary phase.

本项目研究细菌对糖摄取系统的调控策略。在这些系统中，表型异质性不仅与表型在给定时间点的统计分布相关，而且与表型转换时间的显著细胞间变异性相关。我们的中心目标是（i）表征异质定时作为一个动态的基因调控策略和（ii）分析竞争糖利用系统的表型异质性。在SPP 1617的第一个资助期，我们对大肠杆菌阿拉伯糖系统单细胞基因表达动力学中的异时性现象进行了详细的实验和理论分析。杆菌我们发现，这种糖利用系统的生理开关行为是不对称的，这样的关闭开关总是快速和均匀的，而打开开关是缓慢的和不均匀的时间在亚饱和诱导剂水平。我们将这些和突变行为整合到一个单一的定量模型中。关于（ii），我们研究了细胞生长的两个竞争的PTS基板，山梨醇和N-乙酰葡糖胺（Nag），在广泛的外部基板浓度，同时定量表达的Nag和山梨醇利用系统的单细胞水平。我们的数据支持一个模型的分层相互作用，打破了允许随机共利用在低浓度的主导糖（Nag）。在SPP的第二阶段，我们计划研究糖利用系统行为中观察到的表型异质性的可能益处。我们的理论分析预测，异质定时可以是一个有用的赌注对冲策略在稳定期：异质定时可以最大限度地减少诱导昂贵的基因表达的风险后，感测营养源，可能是短暂的，消失之前，细胞从其表达投资中受益。为了量化稳定期基因表达的成本，我们将测量诱导型启动子的无偿基因表达对适应性指标（如活力、代谢活性、膜电位和膜完整性）的影响。我们还将寻求确定限制稳定期细胞总基因表达能力的能量和/或资源库。所获得的数据将被整合到一个定量的成本效益分析的稳定期基因表达，这将是一个实验良好的理论分析的基础上有益的调控策略。本提案的建模部分的另一个任务是分析大肠杆菌中的营养传感信号网络。大肠杆菌，在过渡到稳定期时被激活。