THE GLUCOSE-DEHYDROGENASE MEDIATED ENERGIZATION OF ACINETOBACTER-CALCOACETICUS AS A TOOL FOR EVALUATING ITS SUSCEPTIBILITY TO, AND DEFENSE AGAINST, HAZARDOUS CHEMICALS

Cells of Acinetobacter calcoaceticus 69-V could be energized by glucos e oxidation after the growth on acetate, ethanol, hexanol and benzoate . The velocities of glucose oxidation-driven ATP syntheses were relati vely constant in the range from pH 5.4 to 7.5. With decreasing pH valu es (7.0, 6.0, 5.4) ATP synthesis was inhibited more strongly by the ac tion of 2,4-dinitrophenol and at the same pH value glucose oxidation w as nearly unimpaired or inhibited more weakly. This finding is express ed by a decrease of the P/O ratios, indicating the uncoupling of the e lectron-transport phosphorylation by 2,4-dinitrophenol. The sensitivit y towards this uncoupling effect was higher in ethanol-grown cells of Acinetobacter calcoaceticus 69-V than in hexanol- or acetate-grown cel ls. This increase in sensitivity was accompanied by a decrease of the ratio of saturated (mainly C16:0)to unsaturated (C16:1, C18:1) fatty a cids in ethanol-grown cells compared with hexanol-grown ones. The know ledge of such differences in the susceptibility and its molecular back ground, e.g. possible substrate-induced changes of the fatty acid comp osition of the cytoplasmic membranes, should help elucidate mechanisms of poisoning by membrane-active hazardous chemicals and develop defen ce strategies.