Bet-hedging and communication in E. coli? - Investigations of heterogeneous gene expression of carbohydrate uptake systems

乳胶操纵子的双稳态表达早已为人所知。尽管无偿诱导剂诱导这种表达模式的分子机制已经被阐明，但还没有关于原始底物乳糖诱导或试图阐明这种表达的潜在益处的研究。手头的项目将分析在低水平乳糖诱导后乳胶操纵子表达的异质性，乳糖是细胞活跃代谢的天然底物。将对诱导细胞的潜在生长益处进行调查。该项目的另一个重要方面将是分析不同乳胶操纵子表达中的cAMP。众所周知，cAMP在大肠杆菌中代表饥饿信号，并影响大多数碳水化合物摄取系统的表达。然而，从来没有详细调查过营地控制的根本原因。由于大多数cAMP被排出到介质中，这种分子不仅在细胞内，而且在种群水平上都有可能作为饥饿信号。在该项目框架内开展的调查将涉及这一主题。最后，如果细胞受到两种不同碳水化合物的低浓度影响，我们将分析碳水化合物摄取系统的诱导特性。不同的诱导模式是可能的，细胞诱导摄取两种底物、一种底物或不摄取任何底物。这些结果有望为可能的套期保值策略和大肠杆菌的社会生物学提供有趣的见解。

Bistable expression of the lac operon has been known for quite a long time. Although the molecular mechanisms of this expression pattern provoked by gratuitous inducers have been clarified, no investigations are available that deal with induction by the original substrate lactose or that try to elucidate the potential benefit of this expression. The project at hand will analyze heterogeneity of lac operon expression after induction with low levels of lactose, the natural substrate that is actively metabolized by the cells. A potential growth benefit of induced cells will be investigated. Another important aspect of the project will be the analysis of cAMP in heterogeneous lac operon expression. It is well established that cAMP represents a hunger signal in E. coli and influences the expression of most carbohydrate uptake systems. Nevertheless the reasons underlying cAMP control have never been investigated in detail. As most cAMP is expelled into the medium this molecule has the potential to serve as a hunger signal not only at the cellular but also at the population level. The investigations carried out in the frame of this project will deal with this topic. Lastly, we will analyze induction properties of carbohydrate uptake systems if cells are subjected to low concentrations of two different carbohydrates. Different induction patterns are possible, cells that induce uptake of both substrates, of one substrate or of none. The results promise to give interesting insights into possible bet-hedging strategies and sociobiology of E. coli.