Transfer and expression of a hydrocarbon-degrading plasmid pHCL from Pseudomonas putida to marine bacteria

Transfer of a catabolic plasmid from Pseudomonas putida to indigenous marin e bacteria and obligate halophilic bacteria was carried out under both in v itro and in situ conditions. The marine recipients, which could not otherwi se grow on hydrocarbon substrates, were able to degrade them after the hori zontal transfer of the catabolic plasmid from P. putida. Mating conducted o n nutrient plates yielded comparatively more transconjugants than in broth mating under laboratory conditions (10(6) c.f.u./ml). The transconjugants s tably maintained the plasmid when they were maintained in seawater amended with selective pressure (antibiotics/Hg (25 mug/mul) even after 30 days, wh ereas under non-selective conditions they progressively lost the plasmid af ter 24 days. The expression of the plasmid in the marine recipients was inv estigated by gas chromatographic analysis. The overall objective of this st udy is to evolve a novel strategy for bioremediation of oil spills and the results of the present study suggest that the present approach would offer a better solution for the removal of harmful substances from the environmen t by avoiding serious interference with the microbial flora of the ecosyste m.