Selection of a Pseudomonas cepacia strain constitutive for the degradation of trichloroethylene

Abstract

Tn5 insertion mutants of Pseudomonas cepacia G4 that were unable to degrade trichloroethylene (TCE), toluene, or phenol or to transform m- trifluoromethyl phenol (TFMP) to 7,7,7-trifluoro-2-hydroxy-6-oxo-2,4- heptadienoic acid (TFHA) were produced. Spontaneous reversion to growth on phenol or toluene as the sole source of carbon was observed in one mutant strain, G4 5223, at a frequency of ~1 x 10-4 per generation. One such revertant, G4 5223-PR1, metabolized TFMP to TFHA and degraded TCE. Unlike wild-type G4, G4 5223-PR1 constitutively metabolized both TFMP and TCE without aromatic induction. G4 5223-PR1 also degraded cis-1,2- dichloroethylene, trans-1,2-dichloroethylene, and 1,1-dichloroethylene and oxidized naphthalene to alpha naphthol constitutively. G4 5223-PR1 exhibited a slight retardation in growth rate at TCE concentrations of ≥530 μM, whereas G4 (which was unable to metabolize TCE under the same noninducing growth conditions) remained unaffected. The constitutive degradative phenotype of G4 5223-PR1 was completely stable through 100 generations of nonselective growth.