Mulder M M, Van der Gulden H M, Postma P W, Van Dam K
Laboratory of Biochemistry, University of Amsterdam, The Netherlands.
J Gen Microbiol. 1988 Mar;134(3):777-83. doi: 10.1099/00221287-134-3-777.
The steady-state bacterial dry wt of Escherichia coli, growing under K+-limited conditions in the chemostat, was inversely dependent on the growth rate. This phenomenon was more carefully investigated in medium-flow stop experiments. Growth did not stop immediately but continued for a time, initially at the same rate as before. The dry wt increased to a value corresponding to a steady-state growth rate near zero, independent of the initial specific growth rate. This was observed in both the wild-type strain and a mutant that lacked the high-affinity K+ uptake system. The wild-type strain maintained a low extracellular K+ concentration both in the chemostat under steady-state conditions and after stopping the medium flow. The mutant, on the other hand, maintained a much higher extracellular K+ concentration in the steady state, which decreased to much lower values after stopping the medium flow. From the increase in bacterial dry wt and the low external K+ concentration after stopping the medium flow it is concluded that the intracellular K+ is redistributed among the cells, including new cells. The growth yield on K+ was highest in the stationary growth phase of a batch culture and all steady-state cultures converged ultimately to this yield value after the medium flow had been stopped. It is proposed that the growth rate of E. coli under K+-limited conditions is determined by the intracellular K+ concentration.
在恒化器中钾离子限制条件下生长的大肠杆菌的稳态细菌干重与生长速率呈负相关。在培养基流动停止实验中对这一现象进行了更深入的研究。生长并非立即停止，而是持续一段时间，最初与之前的速率相同。干重增加到与接近零的稳态生长速率相对应的值，与初始比生长速率无关。在野生型菌株和缺乏高亲和力钾离子摄取系统的突变体中均观察到了这一现象。野生型菌株在稳态条件下的恒化器中以及停止培养基流动后都维持较低的细胞外钾离子浓度。另一方面，突变体在稳态下维持着高得多的细胞外钾离子浓度，在停止培养基流动后该浓度降至低得多的值。从停止培养基流动后细菌干重的增加以及低细胞外钾离子浓度可以得出结论，细胞内的钾离子在包括新细胞在内的细胞间重新分布。在分批培养的稳定生长阶段，钾离子的生长产量最高，并且在停止培养基流动后，所有稳态培养物最终都收敛到该产量值。有人提出，在钾离子限制条件下大肠杆菌的生长速率由细胞内钾离子浓度决定。
