Research Product

Survival of genetically altered Pseudomonas putida strains harboring an inducible plasmid, pRO101, or a constitutive plasmid, pRO103, was compared. These plasmids encoded for the degradation of 2,4-dichlorophenoxyacetate (TFD) to 2-chloromaleylacetate, and the maintenance of either plasmid did not alter survival of P. putida PPO301 (pRO101) or PPO301 (pRO103) in an unamended agricultural soil. In a parallel study, Raphanus sativus (radish) seeds failed to germinate in uninoculated and PPO301-inoculated soil amended with 500 ppm TFD. Seed germination was 53 and 80% in soils inoculated with PPO301 (pRO101) and PPO301 (pRO103), respectively (P less than 0.001). However, the difference in the rate of TFD degradation between the native soil and soil inoculated with plasmid-bearing P. putida was probably related to the relatively high inoculum density of P. putida strains (10 to the eighth power cfu) and the relatively low population density of TFD metabolizers indigenous to the soil.