EVALUATION OF POSSIBLE HORIZONTAL GENE-TRANSFER FROM TRANSGENIC PLANTS TO THE SOIL BACTERIUM ACINETOBACTER-CALCOACETICUS BD413

The use of genetically engineered crop plants has raised concerns abou t the transfer of their engineered DNA to indigenous microbes in soil. We have evaluated possible horizontal gene transfer from transgenic p lants by natural transformation to the soil bacterium Acinetobacter ca lcoaceticus BD413. The transformation frequencies with DNA from two so urces of transgenic plant DNA and different forms of plasmid DNA with an inserted kanamycin resistance gene, nptII, were measured. Clear eff ects of homology were seen on transformation frequencies, and no trans formants were ever detected after using transgenic plant DNA. This imp lied a transformation frequency of less than 10(-13) (transformants pe r recipient) under optimised conditions, which is expected to drop eve n further to a minimum of 10(-16) due to soil conditions and a lowered concentration of DNA available to cells. Previous studies have shown that chromosomal DNA released to soil is only available to A. calcoace ticus for limited period of time and that A. calcoaceticus does not ma intain detectable competence in soil. Taken together, these results su ggest that A. calcoaceticus does not take up non-homologous plant DNA at appreciable frequencies under natural conditions.