Research Product

Recent concern over the release of genetically engineered organisms has resulted in a need for information about the potential for gene transfer in the environment. We examined the potential for conjugal transfer of the plasmids R68.45 and FP5 by conjugation in a freshwater environment using Pseudomonas aeruginosa as a test system and Fort Loudoun Resevoir, Knoxville, Tennessee as the field site. When genetically well defined plasmid donor and recipient strains were introduced into test chambers suspended in Fort Loudoun Lake, transfer of both plasmids was observed. Conjugation occurred both in the presence and absence of the natural microbial community. The number of transconjugants recovered was lower when the natural community was present. Transfer of the broad-host-range plasmid R68.45 to the organisms other than the introduced recipient was not observed in these chambers but was observed in laboratory simulations when an organism isolated from lakewater was used as the recipient strain. Although the plasmids transferred in laboratory studies were genetically and physically stable, a significant number of transconjugants recovered from the field trials contained deletions and other genetic rearrangements suggesting that factors which increase gene instability are operating in the environment. The potential for conjugal transfer of R68.45 and FP5 in a freshwater environment exists but detection of transconjugants is significantly reduced by the indigenous microbial population.