Behavior in agricultural soils of a recombinant Pseudomonas bacterium that simultaneously degrades alkyl- and haloaromatics

Pseudomonas sp. FR1 (pFRC20P) is a recombinant bacterium able simultaneously to degrade alkyl- and haloaromatics due to the xylXYZL and xylS genes from the TOL plasmid borne on the bacterial chromosome, and to the gene encoding for a gamma-lactone isomerase from Alcaligenes eutrophus on pFRC20P. The survival of this strain in sterile soils was shown to depend on the physicochemical properties of the soil. The recombinant information was stable in bacteria introduced in soils and conferred selective advantage to the host bacterium when the soils were amended with low amounts of p-methylbenzoate. However, relatively high amounts of this chemical significantly reduced survival of the bacterium. Survival was more seriously affected by chlorobenzoates than by methylbenzoates. Evolution of 14CO2 from p-methyl-14C-benzoate in soils confirmed that Pseudomonas sp. FR1 (pFRC20P) functions in a complex system in accordance with its design. Survival of Pseudomonas sp. FR1 (pFRC20P) was better at 4 degrees C and 25 degrees C than at 37 degrees C. On plates, the pFRC20P plasmid was mobilized by helper plasmids to P. putida at a frequency of about 10(-6) transconjugants per recipient. However, no transfer of recombinant DNA integrated on the chromosome was found, nor was lateral transfer of the recombinant DNA borne by Pseudomonas sp. FR1 (pFRC20P) detected in soils.