Natural transformation of Acinetobacter sp strain BD413 with cell lysates of Acinetobacter sp., Pseudomonas fluorescens, and Burkholderia cepacia in soil microcosms

To elucidate the biological significance of dead bacterial tells in soil to the intra- and interspecies transfer of gene fragments by natural transfor mation, we hare exposed the kanamycin-sensitive recipient Acinetobacter sp, strain BD413(pFG4) to lysates of the kanamycin-resistant donor bacteria Ac inetobacter spp,, Pseudomonas fluorescens, and Burkholderia cepacia, Detect ion of gene transfer was facilitated by the recombinational repair of a par tially (317 bp) deleted kanamycin resistance gene in the recipient bacteriu m. The investigation revealed a significant potential of these DNA sources to transform Acinetobacter spp. residing both in sterile and in nonsterile silt loam soil. seat-treated (80 degrees C, 15 min) cell lysates were capab le of transforming strain BD413 after 4 days of incubation in sterile soil and for up to 8 h in nonsterile soil. Transformation efficiencies obtained in vitro and in situ with the various lysates were similar to or exceeded t hose obtained with conventionally purified DNA. The presence of cell debris did not inhibit transformation in soil, and the debris may protect DNA fro m rapid biological inactivation. Natural transformation thus provides Acine tobacter spp. with an efficient mechanism to access genetic information fro m different bacterial species in soil. The relatively short-term biological activity (e.g., transforming activity) of chromosomal DNA in soil contrast s the earlier reported long-term physical stability of DNA, where fractions have been found to persist for several weeks in sob, Thus, there seems to be a clear difference between the physical and the functional significance of chromosomal DNA in soil.