GENE-TRANSFER OF ALCALIGENES-EUTROPHUS JMP134 PLASMID PJP4 TO INDIGENOUS SOIL RECIPIENTS

This study evaluated the potential for gene transfer of a large catabo lic plasmid from an introduced organism to indigenous soil recipients, The donor organism Alcaligenes eutrophus JMP134 contained the 80-kb p lasmid pJP4, which contains genes that code for mercury resistance. Ge nes on this plasmid plus chromosomal genes also allow degradation of 2 ,4-dichlorophenoxyacetic acid (2,4-D). When JMP134,vas inoculated into a nonsterile soil microcosm amended with 1,000 mu g of 2,4-D g(-1), s ignificant (10(6) g of soil(-1)) populations of indigenous recipients or transconjugants arose. These transconjugants all contained an 80-kb plasmid similar in size to pJP4, and all degraded 2,4-D. In addition, all transconjugants were resistant to mercury and contained the tfdB gene of pJP4 as detected by PCR. No mercury-resistant, 2,4-D-degrading organisms with large plasmids or the tfdB gene were found in the 2,4- D-amended but uninoculated control microcosm. These data clearly show that the plasmid pJP4 was transferred to indigenous soil recipients. E ven more striking is the fact that not only did the indigenous transco njugant population survive and proliferate but also enhanced rates of 2,4-D degradation occurred relative to microcosms in which no such gen e transfer occurred. Overall, these data indicate that gene transfer f rom introduced organisms is an effective means of bioaugmentation and that survival of the introduced organism is not a prerequisite for bio degradation that utilizes introduced biodegradative genes.