Herbicide-tolerant Zoysia grass has been previously
developed through Agrobacterium-mediated transformation.
We investigated the effects of genetically modified (GM)
Zoysia grass and the associated herbicide application on
bacterial community structure by using culture-independent
approaches. To assess the possible horizontal gene transfer
(HGT) of transgenic DNA to soil microorganisms, total
soil DNAs were amplified by PCR with two primer sets
for the bar and hpt genes, which were introduced into the
GM Zoysia grass by a callus-type transformation. The
transgenic genes were not detected from the total genomic
DNAs extracted from 1.5 g of each rhizosphere soils of
GM and non-GM Zoysia grasses. The structures and
diversities of the bacterial communities in rhizosphere
soils of GM and non-GM Zoysia grasses were investigated
by constructing 16S rDNA clone libraries. Classifier,
provided in the RDP II, assigned 100 clones in the 16S
rRNA gene sequences library into 11 bacterial phyla. The
most abundant phyla in both clone libraries were
Acidobacteria and Proteobacteria. The bacterial diversity
of the GM clone library was lower than that of the non-
GM library. The former contained four phyla, whereas
the latter had seven phyla. Phylogenetic trees were
constructed to confirm these results. Phylogenetic analyses
of the two clone libraries revealed considerable difference
from each other. The significance of difference between
clone libraries was examined with LIBSHUFF statistics.
LIBSHUFF analysis revealed that the two clone libraries
differed significantly (P<0.025), suggesting alterations in
the composition of the microbial community associated
with GM Zoysia grass.

Keywords: Transgenic Zoysia grass, PCR, horizontal gene transfer, 16S rRNA gene, bacterial diversity