Electrophysiological effects of Bacillus sphaericus binary toxin on cultured mosquito cells

The electrophysiological effects of both trypsinactivated native and 42- and 51-kDa cloned binary toxins of Bacillus sphaericus were investigated on cultured Culex quinquefasciatus cells using the patchclamp technique. Rates of reduction in whole-cell membrane resistance were correlated with increasing native toxin concentration. The 42- or 51-kDa cloned toxin alone at 50 micrograms/ml reduced the resistance. Electrophysiological effects occurred before any changes were visible by phase-contrast microscopy.