Mikkola R, Kurland C G
Department of Molecular Biology, Uppsala University, Sweden.
Biochimie. 1991 Dec;73(12):1551-6. doi: 10.1016/0300-9084(91)90190-c.
We have determined the relative concentrations of ribosomes accumulated under different growth conditions for a number of translational mutants as well as for some natural isolates of Escherichia coli. The mutants are a tRNA modification mutant (miaA), a streptomycin resistant (SmR) and a streptomycin pseudodependent (SmP) mutant as well as two ribosome ambiguity (ram) mutants. The natural isolates used in this study are known to function with submaximal ribosome kinetics. The data show that for all the ribosome mutants the concentration of ribosomes relative to that in wild type bacteria increases when the growth rate decreases. A small increase is also seen in the natural isolates. In contrast, the miaA mutant shows no increase in ribosome concentration under the same slow growth conditions. The results suggest that bacteria with kinetically impaired ribosomes can to some extent increase the number of ribosomes accumulated under poor growth conditions in order to compensate for their slower function. We use this observation to explain in part how bacteria growing in natural environments can escape the strong selection for maximized growth rates and for optimized ribosomes that are characteristic of laboratory strains.
我们已经测定了许多翻译突变体以及一些大肠杆菌自然分离株在不同生长条件下积累的核糖体的相对浓度。这些突变体包括一个tRNA修饰突变体（miaA）、一个链霉素抗性（SmR）和一个链霉素假依赖性（SmP）突变体以及两个核糖体模糊性（ram）突变体。已知本研究中使用的自然分离株在亚最大核糖体动力学条件下起作用。数据表明，对于所有核糖体突变体，当生长速率降低时，相对于野生型细菌，核糖体的浓度会增加。在自然分离株中也观察到了小幅增加。相比之下，在相同的缓慢生长条件下，miaA突变体的核糖体浓度没有增加。结果表明，核糖体动力学受损的细菌可以在一定程度上增加在不良生长条件下积累的核糖体数量，以补偿其较慢的功能。我们利用这一观察结果部分解释了在自然环境中生长的细菌如何能够逃避对最大生长速率和优化核糖体的强烈选择，而这些是实验室菌株的特征。
