Ahmed S, Booth I R
J Gen Microbiol. 1983 Aug;129(8):2521-9. doi: 10.1099/00221287-129-8-2521.
The effect of three beta-galactosides on the components membrane potential (delta psi) and pH gradient (delta pH) of protonmotive force and growth of Escherichia coli has been examined. A good correlation between the reduction of the protonmotive force and growth inhibition was observed. Thus some galactosides had little effect on either the protonmotive force or growth while lactose diminished the protonmotive force and caused growth inhibition. This effect of lactose was dependent on the ionic composition of the growth media. In Medium A (77 mM-Na+, 85 mM-K+) lactose diminished delta psi but had no effect on delta pH. Growth inhibition was transient at an external pH 6.0 but complete at pH 7.5. In medium KA (approximately 1 mM-Na+, 162 mM-K+) delta pH was diminished and delta psi was not affected and consequently growth inhibition was complete at pH 6.0. In medium NA (163 mM-Na+, 20 mM-K+) lactose had little effect on delta psi, delta pH or growth. These data support Skulachev's hypothesis of buffering of the protonmotive force by K+ and Na+ gradients.
研究了三种β-半乳糖苷对大肠杆菌质子动力势的膜电位（Δψ）和pH梯度（ΔpH）以及生长的影响。观察到质子动力势的降低与生长抑制之间存在良好的相关性。因此，一些半乳糖苷对质子动力势或生长几乎没有影响，而乳糖会降低质子动力势并导致生长抑制。乳糖的这种作用取决于生长培养基的离子组成。在培养基A（77 mM - Na⁺，85 mM - K⁺）中，乳糖降低了Δψ，但对ΔpH没有影响。在外部pH 6.0时生长抑制是短暂的，但在pH 7.5时是完全的。在培养基KA（约1 mM - Na⁺，162 mM - K⁺）中，ΔpH降低，Δψ不受影响，因此在pH 6.0时生长抑制是完全的。在培养基NA（163 mM - Na⁺，20 mM - K⁺）中，乳糖对Δψ、ΔpH或生长几乎没有影响。这些数据支持了Skulachev关于K⁺和Na⁺梯度对质子动力势进行缓冲的假说。
