Survival in soil of different toluene-degrading Pseudomonas strains after solvent shock.

We assayed the tolerance to solvents of three toluene-degrading Pseudomonas putida strains and Pseudomonas mendocina KR1 in liquid and soil systems. P. putida DOT-T1 tolerated concentrations of heptane, propylbenzene, octanol, and toluene of at least 10% (vol/vol), while P. putida F1 and EEZ15 grew well in the presence of 1% (vol/vol) propylbenzene or 10% (vol/vol) heptane, but not in the presence of similar concentrations of octanol or toluene. P. mendocina KR1 grew only in the presence of heptane. All three P. putida strains were able to become established in a fluvisol soil from the Granada, Spain, area, whereas P. mendocina KR1 did not survive in this soil. The tolerance to organic solvents of all three P. putida strains was therefore assayed in soil. The addition to soil of 10% (vol/wt) heptane or 10% (vol/wt) propylbenzene did not affect the survival of the three P. putida strains. However, the addition of 10% (vol/wt) toluene led to an immediate decrease of several log units in the number of CFU per gram of soil for all of the strains, although P. putida F1 and DOT-T1 subsequently recovered. This recovery was influenced by the humidity of the soil and the incubation temperature. P. putida DOT-T1 recovered from the shock faster than P. putida F1; this allowed the former strain to become established at higher densities in polluted sites into which both strains had been introduced.