Bulthuis B A, Koningstein G M, Stouthamer A H, van Verseveld H W
Department of Microbiology, Vrije Universiteit, Amsterdam, The Netherlands.
Antonie Van Leeuwenhoek. 1993 Jan;63(1):1-16. doi: 10.1007/BF00871725.
The magnitude of the proton motive force (delta p) and its constituents, the electrical (delta psi) and chemical potential (-Z delta pH), were established for chemostat cultures of a protease-producing, relaxed (rel-) variant and a not protease-producing, stringent (rel+) variant of an industrial strain of Bacillus licheniformis (respectively referred to as the A- and the B-type). For both types, an inverse relation of delta p with the specific growth rate mu was found. The calculated intracellular pH (pHin) was not constant but inversely related to mu. This change in pHin might be related to regulatory functions of metabolism but a regulatory role for pHin itself could not be envisaged. Measurement of the adenylate energy charge (EC) showed a direct relation with mu for glucose-limited chemostat cultures; in nitrogen-limited chemostat cultures, the EC showed an approximately constant value at low mu and an increased value at higher mu. For both limitations, the ATP/ADP ratio was directly related to mu. The phosphorylation potential (delta G'p) was invariant with mu. From the values for delta G'p and delta p, a variable -->H+/ATP-stoichiometry was inferred: -->H+/ATP = 1.83 +/- 0.52 mu, so that at a given -->H+/O-ratio of four (4), the apparent P/O-ratio (inferred from regression analysis) showed a decline of 2.16 to 1.87 for mu = 0 to mu max (we discuss how more than half of this decline will be independent of any change in internal cell-volume). We propose that the constancy of delta G'p and the decrease in the efficiency of energy-conservation (P/O-value) with increasing mu are a way in which the cells try to cope with an apparent less than perfect coordination between anabolism and catabolism to keep up the highest possible mu with a minimum loss of growth-efficiency. Protease production in nitrogen-limited cultures as compared to glucose-limited cultures, and the difference between the A- and B-type, could not be explained by a different energy-status of the cells.
测定了地衣芽孢杆菌工业菌株产生蛋白酶的松弛型（rel-）变体和不产生蛋白酶的严谨型（rel+）变体（分别称为 A 型和 B 型）在恒化器培养中的质子动力势（Δp）及其组成部分，即电势（Δψ）和化学势（-ZΔpH）。对于这两种类型，均发现Δp 与比生长速率μ呈反比关系。计算得出的细胞内 pH（pHin）并非恒定不变，而是与μ呈反比关系。pHin 的这种变化可能与代谢的调节功能有关，但无法设想 pHin 自身具有调节作用。对腺苷酸能荷（EC）的测量表明，在葡萄糖限制的恒化器培养中，EC 与μ呈直接关系；在氮限制的恒化器培养中，EC 在低μ时显示出近似恒定的值，而在较高μ时则增加。对于这两种限制情况，ATP/ADP 比值均与μ呈直接关系。磷酸化势（ΔG'p）不随μ变化。根据ΔG'p 和Δp 的值，推断出可变的 H⁺/ATP 化学计量关系：H⁺/ATP = 1.83 ± 0.52μ，因此在给定的 H⁺/O 比值为 4 时，表观 P/O 比值（通过回归分析推断）在μ从 0 到μmax 时从 2.16 下降到 1.87（我们讨论了这种下降的一半以上将如何与细胞内体积的任何变化无关）。我们提出，ΔG'p 的恒定性以及随着μ增加能量守恒效率（P/O 值）的降低，是细胞试图应对合成代谢和分解代谢之间明显不太完美的协调的一种方式，以便在生长效率损失最小的情况下保持尽可能高的μ。与葡萄糖限制培养相比，氮限制培养中的蛋白酶产生以及 A 型和 B 型之间的差异，无法通过细胞不同的能量状态来解释。
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