ous microcosm studies have been described. Purified
DNA and plasmid DNA can persist for several weeks in
soil (Lorenz and Wackernagel 1987; Romanowski et al.
1993; Widmer et al. 1996), and marker DNA harbored in
tobacco plants and poplar trees can last for 2 to 3 months
(Widmer et al. 1997; Hay et al. 2002). We previously
demonstrated that transgenes in leaf samples of virusresistant
transgenic chili peppers last up to 3 months in soil
(Lee et al. 2007). Gebhard and Smalla (1998) have shown
that the NPTII marker gene in transgenic sugar beets can
persist up to 2 years under field conditions. Such long-term
persistence, even by a small percentage of the DNA
released from plants, is considered sufficient for transformation
to soil-borne microorganisms (Smalla et al. 2000).
Multiple investigations have focused on gene transfer from
transgenic plants to soil microorganisms (Hoffmann et al.
1994; Lorenz and Wackernagel 1994; Nielsen et al. 1997b,
1998). For example, de Vries and Wackernagel (1998) and
Gebhard and Smalla (1998) have demonstrated that
transgenic plant DNA can be integrated into Acinetobacter
sp. BD413 DNA by homologous recombination under
optimized laboratory conditions. However, because gene
transfer within the natural environment has not yet been