A scientific study.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&l
ist_uids=16499967&dopt=Abstract

Occurrence and persistence of Bacillus thuringiensis (Bt) and
transgenic Bt corn cry1Ab gene from an aquatic environment.
Douville M, Gagne F, Blaise C, Andre C.

Environment Canada, St. Lawrence Centre, 105 McGill Street, Montreal,
Que., Canada H2Y 2E7.

Genetically modified corn crops and suspensions of Bacillus
thuringiensis (Bt) are currently used to control pest infestations of
insects of the Lepidoptera family. For this purpose, the cry1Ab gene
coding for protein delta-endotoxin derived from B. thuringiensis
kurstaki (Btk), which is highly toxic to these insects, was inserted
and expressed in corn. The aims of this study were to examine the
occurrence and persistence of the cry1Ab gene from Btk and Bt corn in
aquatic environments near fields where Bt corn was cultivated. First,
an optimal DNA preparation and extraction methodology was developed
to allow for quantitative gene analysis by real-time polymerase chain
reaction (qPCR) in various environmental matrices. Second, surface
water and sediment were spiked in vitro with genomic DNA from Bt or
Bt corn to evaluate the persistence of cry1Ab genes. Third, soil,
sediment, and water samples were collected before seeding, 2 weeks
after pollen release, and after corn harvesting and mechanical root
remixing in soils to assess cry1Ab gene content. DNA was extracted
with sufficient purity (i.e., low absorbance at 230 nm and absence of
PCR-inhibiting substances) from soil, sediment, and surface water.
The cry1Ab gene persisted for more than 21 and 40 days in surface
water and sediment, respectively. The removal of bacteria by
filtration of surface water samples did not significantly increase
the half-life of the transgene, but the levels were fivefold more
abundant than those in unfiltered water at the end of the exposure
period. In sediments, the cry1Ab gene from Bt corn was still detected
after 40 days in clay- and sand-rich sediments. Field surveys
revealed that the cry1Ab gene from transgenic corn and from naturally
occurring Bt was more abundant in the sediment than in the surface
water. The cry1Ab transgene was detected as far away as the Richelieu
and St. Lawrence rivers (82 km downstream from the corn cultivation
plot), suggesting that there were multiple sources of this gene
and/or that it undergoes transport by the water column. Sediment-
associated cry1Ab gene from Bt corn tended to decrease with distance
from the Bt cornfield. Sediment concentrations of the cry1Ab gene
were significantly correlated with those of the cry1Ab gene in
surface water (R=0.83;P=0.04). The data indicate that DNA from Bt
corn and Bt were persistent in aquatic environments and were detected
in rivers draining farming areas.

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