Ramagopal S
Eur J Biochem. 1984 Apr 16;140(2):353-61. doi: 10.1111/j.1432-1033.1984.tb08108.x.
The metabolism of ribosomes during the exponential growth and post-exponential phase of Escherichia coli cells was investigated. Incubation of E. coli cells in two rich media: L-broth and phosphate medium, up to stationary phase shows no drop in viability or any changes in ribosomes. However, the survival rate during prolonged culture of the post-stationary-phase cells has been found to be a function of the incubation medium. The decline in viability is only slight in phosphate medium but very rapid in L-broth. So long as the viability is maintained, the level of ribosomes and the relative abundance of rRNA and ribosomal proteins in ribosomes of the post-stationary cultures are remarkably stable and are similar to exponentially growing cells. On the other hand, post-stationary cultures undergoing a rapid drop in cell viability lose 95% of the original ribosomes. These cultures accumulate a large pool of 30S and 50S subunits and a few 70S monosomes, all of which show deficiency in the various ribosomal proteins. No differences in rRNA can be detected but the number and the relative stoichiometry of individual ribosomal proteins are drastically altered. Only 13 of the 53 proteins known in the E. coli ribosome appeared in the same relative amounts as in the ribosomes of the exponentially growing cells. Six proteins (S12, S21, L2, L16, L20, L34) are completely lost and all others undergo partial loss. An analysis of the number and relative abundance of ribosomal proteins in the whole cells, as oppossed to isolated ribosomes, suggests that during the initial stages of the catabolism of ribosomes a crucial step is the formation of ribosomal-subunit-membrane complexes. The data emphasize the role of the constituents of ribosomes not only for the growth but also for the survival of E. coli cells. A model for the metabolism of ribosomes during the exponential growth and post-exponential phase of E. coli is presented.
对大肠杆菌细胞指数生长期和指数生长后期核糖体的代谢进行了研究。将大肠杆菌细胞在两种丰富培养基（L肉汤和磷酸盐培养基）中培养至稳定期，细胞活力没有下降，核糖体也没有任何变化。然而，已发现稳定期后细胞长期培养期间的存活率是培养培养基的函数。在磷酸盐培养基中活力下降很轻微，但在L肉汤中下降非常迅速。只要保持活力，稳定期后培养物核糖体中核糖体的水平以及rRNA和核糖体蛋白的相对丰度就非常稳定，并且与指数生长期的细胞相似。另一方面，细胞活力迅速下降的稳定期后培养物会损失95%的原始核糖体。这些培养物积累了大量的30S和50S亚基以及少量的70S单体，所有这些都显示出各种核糖体蛋白的缺乏。未检测到rRNA有差异，但单个核糖体蛋白的数量和相对化学计量发生了剧烈变化。在大肠杆菌核糖体中已知的53种蛋白质中，只有13种以与指数生长期细胞核糖体相同的相对量出现。六种蛋白质（S12、S21、L2、L16、L20、L34）完全缺失，其他所有蛋白质都部分缺失。对全细胞中核糖体蛋白数量和相对丰度的分析表明，与分离的核糖体相反，在核糖体分解代谢的初始阶段，一个关键步骤是核糖体亚基-膜复合物的形成。这些数据强调了核糖体成分不仅对大肠杆菌细胞生长而且对其存活的作用。提出了大肠杆菌指数生长期和指数生长后期核糖体代谢的模型。
