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

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.