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-tolerant strain Pseudomonas putida Px51T was not reproducible in the presence of harmful organic solvents, such as p-xylene and toluene. The survival often fluctuated the during late exponential phase of growth. The repetitive growth was obtained by maintaining pO2 20-40% (v/v) in the culture flask. However, even under these aerobic conditions, the cells starved for a carbon source were killed by exposure to harmful solvents. The tolerance to organic solvents was lowered greatly by treatment with a proton conductor, carbonyl 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 usually tolerates. These results indicate that the solvent tolerance of Px51T depends upon on energy produced by aerobic respiration.