Post-Exponential Phase Gene Expression in Escherichia coli

大肠杆菌中指数后期基因表达

• 批准号: RGPIN-2015-06187
• 负责人: Schellhorn, Herb
• 金额: $ 2.77万
• 依托单位: McMaster University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=687187
• 关键词: Post; Exponential; Phase; Gene; Expression

Many bacterial genes that are important for adaptation and long-term survival are poorly-expressed under the exponential phase conditions. My laboratory has helped to characterize many adaptive genes that ares expressed under nutrient limiting conditions, particularly those that are controlled by the RpoS alternative sigma factor in Escherichia coli. We have shown that the non-essential rpoS gene, while important for long-term survival, may be lost under selection as rpoS mutants have enhanced metabolic capability for growth on non-preferred carbon sources. These studies, combined with our gene expression studies, continue to be a major focus for my laboratory. We have recently found that other poorly-understood regulatory processes, in addition to and independent of RpoS, are important for long-term gene expression and these will also be examined. We will construct targeted combinatorial mutants deficient in RpoS-controlled functions to examine the role in bacterial metabolism using microarray, RNA Seq and next generation sequencing. In addition to characterizing RpoS-dependent genes, we will investigate specific questions that have arisen from our previous studies regarding expression RpoS-dependent paralogs including a key system for balance carbon utilization namely Transaldolase/Transketolase. Each of these stationary-specific genes are likely important in helping the cell adapt to stress conditions since we have found that they are expressed only in stationary phase when cells are in a starved state--they are poorly-expressed under normal conditions. To characterize non-RpoS genes that are highly expressed in long-term (> 1 day) cultures, we will construct appropriate deletion mutants of genes that we have previously identified (unpublished) and will examine bacterial survival using standard plate assays. To extend our studies further, we will also examine post exponential physiology in environmental bacterial isolates. Our long term goal is to enhance our understanding of how bacteria adapt to sub-optimal growth conditions and validate regulatory models for post-exponential gene expression, which have been developed using E. coli laboratory strains of , to natural E. coli populations in the environment. ***Our short term objectives are to: ***1. Examine how expression of the RpoS regulon is controlled by other sigma factors and by the Crl regulatory protein. ***2. Identify and characterize the Post-Stationary Phase (PSP) regulon. ***3. Examine the physiological role of key RpoS-dependent paralogs in E. coli.  *** **

许多对适应和长期存活重要的细菌基因在指数期条件下表达很差。我的实验室已经帮助描述了许多在营养限制条件下表达的适应性基因，特别是那些在大肠杆菌中由RpoS替代σ因子控制的基因。我们已经表明，非必需的rpoS基因，而长期生存的重要性，可能会失去选择的rpoS突变体具有增强的代谢能力的非首选碳源上的增长。这些研究与我们的基因表达研究相结合，仍然是我实验室的主要重点。我们最近发现，其他不太了解的监管过程，除了和独立的RpoS，是重要的长期基因表达，这些也将进行检查。我们将构建Rpos控制功能缺陷的靶向组合突变体，以使用微阵列，RNA Seq和下一代测序来研究其在细菌代谢中的作用。除了表征Rpos依赖性基因，我们将调查我们以前的研究中出现的具体问题，表达Rpos依赖性旁系同源物，包括一个关键系统，平衡碳利用，即转醛醇酶/转酮醇酶。这些静止特异性基因中的每一个在帮助细胞适应应激条件方面可能都很重要，因为我们发现它们只在细胞处于饥饿状态时的静止期表达-它们在正常条件下表达很差。为了表征在长期（> 1天）培养物中高度表达的非RpoS基因，我们将构建我们先前鉴定（未发表）的基因的适当缺失突变体，并将使用标准平板测定法检查细菌存活。为了进一步扩展我们的研究，我们还将研究环境细菌分离株的指数后生理学。我们的长期目标是提高我们对细菌如何适应次优生长条件的理解，并验证指数后基因表达的调控模型，这些模型已经使用E.大肠杆菌实验室菌株与天然E. * 我们的短期目标是：*1。研究RpoS调节子的表达如何受其他sigma因子和Crl调节蛋白的控制。 ***2。鉴定和表征稳定期后（PSP）调节子。 *3。研究关键RpoS依赖性旁系同源物在大肠杆菌中的生理作用。大肠杆菌 *****