Conjugal transfer of R68.45 and FP5 between Pseudomonas aeruginosa strains in a freshwater environment

Abstract

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. In this study, the conjugal transfer in Pseudomonas aeruginosa of the plasmids R68.45 and FP5 was demonstrated in the freshwater environment of Fort Loudoun Resevoir, Knoxville, Tenn. 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 in both 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 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 genetic material must be considered in evaluating the release of any genetically engineered microorganism into a freshwater environment.

Quantification of the effect of substrate concentration on the conjugal transfer rate of the TOL plasmid in short-term batch mating experiments

“…Several researchers have attributed the differences in plasmid transfer frequencies in alternate environments to the difference in substrate levels (Altherr and Kasweck 1982;Mach and Grimes 1982;Trevors and Odie 1986;O'Morchoe et al 1988;Trevors et al 1990). However, these reports did not allow distinction between direct nutrient effects and indirect effects, such as growth-rate stimulation at higher substrate concentration.…”

Risks associated with the application of genetically modified microorganisms in terrestrial ecosystems

“…Plasmid transfer in soil from introduced GEMMOs to indigenous microorganisms, which might be more relevant regarding risk assessment than donor versus recipient experiments was also recently reported [54,55]. Plasmid transfer has also been detected in river epilithon [56], in lake water [57], in sewage [58] and in planta [59]. Transfer of plasmids carrying genes for the breakdown of xenobiotics has been reported to occur in environments polluted with these compounds [35,60,61].…”

Gene transfer among bacteria under conditions of nutrient depletion in simulated and natural aquatic environments

“…O'Morchoe et al [8] found transfer of both R68.45 and FP5 plasmids over a 72 h period in chambers, containing Pseudomonas aeruginosa donor and recipient strains, suspended in a lake (Fort Loudoun Reservoir, Knoxville, Tennessee). Transconjugants were recovered in the absence and presence of the natural microbial community, although in the latter case transconjugant numbers were lower.…”