E. coli aminoglycoside treatment

Aminoglycosides are broad-spectrum antibiotics whose mechanism of action
is under debate. It is widely accepted that membrane voltage potentiates
aminoglycoside activity, which is ascribed to voltage-dependent drug
uptake. In this paper, we measured the response of Escherichia coli
treated with aminoglycosides and discovered that the bactericidal action
arises not from the downstream effects of voltage dependent drug uptake,
but rather directly from dysregulated membrane potential. In the absence
of voltage, aminoglycosides are taken into cells and exert bacteriostatic
effects by inhibiting translation. However, cell killing was immediate
upon re-polarization. The hyperpolarization arose from altered ATP flux,
which induced a reversal of the F1Fo-ATPase to hydrolyze ATP and generated
the deleterious voltage. Heterologous expression of an ATPase inhibitor
completely eliminated bactericidal activity, while loss of the F-ATPase
reduced the electrophysiological response to aminoglycosides. Our data
support a model of voltage induced death, and separates aminoglycoside
bacteriostasis and bactericide in E. coli.