Growth rate regulation in bacteria has been an important issue in bacterial physiology for the past 50 years. This review, using Escherichia coli as a paradigm, summarizes the mechanisms for the regulation of rRNA synthesis in the context of systems biology, particularly, in the context of genome-wide competition for limited RNA polymerase (RNAP) in the cell under different growth conditions including nutrient starvation. The specific location of the seven rrn operons in the chromosome and the unique properties of the rrn promoters contribute to growth rate regulation. The length of the rrn transcripts, coupled with gene dosage effects, influence the distribution of RNAP on the chromosome in response to growth rate. Regulation of rRNA synthesis depends on multiple factors that affect the structure of the nucleoid and the allocation of RNAP for global gene expression. The magic spot ppGpp, which acts with DksA synergistically, is a key effector in both the growth rate regulation and the stringent response induced by nutrient starvation, mainly because the ppGpp level changes in response to environmental cues. It regulates rRNA synthesis via a cascade of events including both transcription initiation and elongation, and can be explained by an RNAP redistribution (allocation) model.

中文翻译：

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大肠杆菌的生长速率调节。

在过去的 50 年里，细菌的生长速率调节一直是细菌生理学中的一个重要问题。这篇综述以大肠杆菌为范例，总结了系统生物学背景下 rRNA 合成的调控机制，特别是在不同生长条件下细胞中有限 RNA 聚合酶 (RNAP) 的全基因组竞争背景下包括营养饥饿。七个 rrn 操纵子在染色体中的特定位置和 rrn 启动子的独特特性有助于调节生长速率。rrn 转录物的长度与基因剂量效应相结合，影响 RNAP 在染色体上的分布以响应生长速率。rRNA 合成的调控取决于影响类核结构和 RNAP 分配以进行全局基因表达的多种因素。与 DksA 协同作用的神奇点 ppGpp 是生长速率调节和营养饥饿引起的严格反应的关键效应物，主要是因为 ppGpp 水平响应环境线索而变化。它通过包括转录起始和延伸在内的一系列事件来调节 rRNA 合成，并且可以通过 RNAP 再分配（分配）模型来解释。