Collins S H, Jarvis A W, Lindsay R J, Hamilton W A
J Bacteriol. 1976 Jun;126(3):1232-44. doi: 10.1128/jb.126.3.1232-1244.1976.
The addition of lactate to lightly buffered suspensions of resting cells of Escherichia coli caused an increase in the pH of the extracellular phase as lactate and protons entered the cell together. From the magnitude of the pH change and the non-electrogenic character of lactate uptake, we concluded that the stoichiometry of the process was 1 proton/lactate anion. The addition of alanine caused a slow increase in pH, also apparently due to the transport of the amino acid by a symport mechanism with 1 proton/alanine stoichiometry. When cells were grown in the chemostat with alanine as sole carbon source and as limiting nutrient, this stoichiometry was found to alter to 2 protons/alanine, and then to 4 protons/alanine. These increases stoichiometries were due to the selection of mutants. The consequences of these changes on the potential uptake capacity of the cells are discussed.
向大肠杆菌静息细胞的轻度缓冲悬浮液中添加乳酸，随着乳酸和质子一起进入细胞，细胞外相的pH值升高。根据pH变化的幅度以及乳酸摄取的非电生性，我们得出该过程的化学计量比为1个质子/乳酸阴离子。添加丙氨酸会导致pH值缓慢升高，这显然也是由于氨基酸通过共转运机制进行转运，化学计量比为1个质子/丙氨酸。当细胞在恒化器中以丙氨酸作为唯一碳源和限制性营养物进行培养时，发现这种化学计量比会变为2个质子/丙氨酸，然后变为4个质子/丙氨酸。这些增加的化学计量比是由于突变体的选择。讨论了这些变化对细胞潜在摄取能力的影响。
