Involvement of adaptive mechanism and an energy-dependent efflux system of Pseudomonas sp. LE2 counteracting insecticide lindane

Abstract

An adaptive mechanism and efflux-transport system of Pseudomonas sp. LE2 counteracting organochlorine insecticide lindane were investigated to understand the survival mechanism of this microorganism in lindane-contaminated environment. Changes in membrane fluidity and fatty acid composition of Pseudomonas sp. LE2 cells grown on glucose either in the presence or absence of lindane were determined. Considerably high ratio of total saturated to unsaturated fatty acids in cells grown on glucose in the presence of lindane was observed as compared to that in cells grown on glucose in the absence of lindane. Lindane significantly affected in vitro the membrane of Pseudomonas sp. LE2 cells by decreasing the fluorescence polarization of membrane probe, 1,6-diphenyl-1,3,5-hexatriene (DPH) inserted into cytoplasmic membrane. Less fluidizing effect of lindane on the membranes of cells that had adapted to lindane was observed. Lindane transport was assessed by incubating cell suspensions with [ 14C]lindane either in the presence or absence of sodium azide, a membrane transport inhibitor, and by measuring the radioactivity in cell pellets. No time-dependent and steady-state increase in the radioactivity of [ 14C]lindane without sodium azide treatment was observed in cell pellets, suggesting simple diffusion mechanism for lindane accumulation in cells. Significant increase in the radioactivity was observed in cell pellets by sodium azide treatment. Sodium azide inhibited the efflux of lindane by Pseudomonas sp. LE2. These results suggest the view that Pseudomonas sp. LE2 capable of growing in the presence of lindane is able to adapt to the fluidizing action of lindane by incorporating the saturated fatty acid into membrane lipids, and eliminate lindane from cells by an energy-dependent efflux mechanism.