In vivo transfer of pR68.45 from Pseudomonas aeruginosa into indigenous soil bacteria

The release of genetically engineered organisms (GEMs) into the environment could result in novel gene sequences becoming transferred to, and established in, the indigenous soil biota. The potential for recombination in nonsterile soil is difficult to determine due to problems isolating transconjugants of indigenous microbes, while concurrently suppressing introduced donors. We have developed a system that allows us to detect the transfer of the plasmid R68.45 from Pseudomonas aeruginosa strain PA025 into the indigenous soil bacterial population. Transconjugants were selected by plating on minimal media containing antibiotics and were verified by DNA-DNA hybridization. The observed maximum transfer frequency was approximately 10(-6). Fatty acid analysis of transconjugants showed that intergeneric transfer was occurring between the introduced organism and genetically dissimilar species.