Effect of membrane-active antibiotics on motility and 42K permeability of Pseudomonas fluorescens

Abstract

Valinomycin, monactin, and nonactin were found to affect the motility of Pseudomonas fluorescens. Cells "loaded" with ⁴²K rapidly exchanged it with K⁺ when exposed to the above compounds, and uptake of such unlabeled K⁺ resulted in a net increase in total potassium content. Hydrogen ions also moved rapidly into the antibiotic-treated organisms, and both potassium and hydrogen ion permeability were used as measures of membrane integrity. Alteration of membranes by these antibiotics suggests a possible relationship between this and diminution of flagellar activity. Membrane-active antibiotics may be useful agents for studying membrane-mediated transformations of chemical into mechanical energy using motile bacteria as model systems.