Little R, Ryals J, Bremer H
J Bacteriol. 1983 Sep;155(3):1162-70. doi: 10.1128/jb.155.3.1162-1170.1983.
We have previously reported the isolation of Escherichia coli rpoB mutants in which the control of ribosome synthesis by the nucleotide effector guanosine tetraphosphate (ppGpp) is altered, owing to a 20-fold increased sensitivity of the mutant RNA polymerases to ppGpp. In these mutants, the level of ppGpp during exponential growth is decreased about 10-fold, relative to that of rpoB+ wild-type strains, such that a near normal partitioning of RNA polymerase occurs with respect to stable RNA (rRNA and tRNA) gene activity. Here, the physiological effects of two different rpoB alleles in a relA+ and relA background were analyzed in greater detail by comparison with their isogenic rpoB+ wild-type parents. For a given growth medium, the rpoB mutations were found to affect four parameters which resulted in a reduction of growth rate. The results reinforce a previous conclusion that a key element in control of the bacterial growth rate is a mutual relationship between control of ribosome synthesis by ppGpp and control of relA-independent ppGpp metabolism by the concentration and function of ribosomes.
我们之前报道过大肠杆菌rpoB突变体的分离情况，在这些突变体中，核苷酸效应物鸟苷四磷酸（ppGpp）对核糖体合成的控制发生了改变，这是由于突变的RNA聚合酶对ppGpp的敏感性提高了20倍。在这些突变体中，相对于rpoB⁺野生型菌株，指数生长期的ppGpp水平降低了约10倍，从而使得RNA聚合酶在稳定RNA（rRNA和tRNA）基因活性方面出现了接近正常的分配。在此，通过与其同基因的rpoB⁺野生型亲本进行比较，更详细地分析了relA⁺和relA背景下两种不同rpoB等位基因的生理效应。对于给定的生长培养基，发现rpoB突变会影响四个参数，这些参数导致生长速率降低。这些结果强化了之前的一个结论，即控制细菌生长速率的一个关键因素是ppGpp对核糖体合成的控制与核糖体浓度和功能对relA非依赖性ppGpp代谢的控制之间的相互关系。
