Kashket E R, Wilson T H
J Bacteriol. 1972 Feb;109(2):784-9. doi: 10.1128/jb.109.2.784-789.1972.
Streptococcus lactis (ATCC 7962) accumulated thiomethyl-beta-galactoside (TMG) and other galactosides against concentration gradients when the cells were supplied with a metabolizable substrate, such as glucose. The accumulated TMG was free and not phosphorylated. In the absence of glucose, TMG rapidly entered the cell to a concentration equal to that of the medium. Agents that uncouple oxidative phosphorylation abolished active transport but not the carrier-facilitated entry of TMG. Evidence that the transport carriers were functional in the absence of glucose or in the presence of uncoupling agents included the demonstration of counterflow, which depends on competitive inhibition for the carrier for exit.
当向乳酸链球菌（ATCC 7962）提供可代谢底物（如葡萄糖）时，该菌能逆浓度梯度积累硫代甲基-β-半乳糖苷（TMG）和其他半乳糖苷。积累的TMG是游离的，未被磷酸化。在没有葡萄糖的情况下，TMG迅速进入细胞，其浓度与培养基中的浓度相等。解偶联氧化磷酸化的试剂可消除主动运输，但不影响载体介导的TMG进入细胞。在没有葡萄糖或存在解偶联剂的情况下，运输载体仍具有功能，这一证据包括逆流的证明，逆流取决于载体对出口的竞争性抑制。
