CONSTRUCTION AND BEHAVIOR OF BIOLOGICALLY CONTAINED BACTERIA FOR ENVIRONMENTAL APPLICATIONS IN BIOREMEDIATION

The survival of microorganisms can be predicted through the use of act ive biological containment systems. We have constructed contained Pseu domonas putida strains that degrade alkylbenzoates. The modified strai n carries a fusion of the P-lac promoter to the gef gene, which encode s a killing protein. Expression from P-lac is controlled through a reg ulatory cascade, so that P-lac is snitched on or off by the absence or presence of alkylbenzoates, respectively. Similar uncontained strains were also constructed and tested as a control. Contained and uncontai ned strains were genetically stable, and their survival and functional ity in soil microcosms were as expected. Both contained and uncontaine d strains survived well in soils supplemented with alkylaromatics, whe reas survival of the contained strain in soil microcosms without methy lbenzoates was markedly reduced, in contrast to the control strain, wh ich survived in these soils in the absence of alkylbenzoates. The TOL plasmid was transferred in soils between Pseudomonas strains but was n ot able to mobilize the elements of the containment system.