Deterioration of tolerance to hydrophobic organic solvents in a toluene-tolerant strain of Pseudomonas putida under the conditions lowering aerobic respiration

The growth curve (increase in the number of viable cells) of a toluene-tole rant strain Pseudomonas putida Px51T was not reproducible in the presence o f harmful organic solvents, such as p-xylene and toluene, The survival of t en fluctuated the during late exponential phase of growth. The repetitive g rowth was obtained by maintaining pO(2) 20-40% (v/v) in the culture flask. However, even under these aerobic conditions, the cells starved for a carbo n source were killed by exposure to harmful solvents. The tolerance to orga nic solvents was lowered greatly by treatment with a proton conductor, carb onyl cyanide m-chlorophenylhydrazone (CCCP), or an electron transport chain inhibitor, sodium azide, Px51T treated with CCCP lost tolerance to a wide variety of organic solvents with log P-ow of 2.6-4.2, which the organism us ually tolerates. These results indicate that the solvent tolerance of Px51T depends upon on energy produced by aerobic respiration.