Transgenic DNA from glyphosate-resistant soybeans was detected in the
intestinal flora of humans.
Manipulated Organism:
Soybean (Glycine max).
Inserted Transgenes:
CP4 EPSPS gene from Agrobacterium, which produces an
herbicide-resistant version of the enzyme targeted by the herbicide
glyphosate (Roundup).
Goal of This Study:
"Human consumption of GM [genetically modified] plants raises the question
of whether transgenes can be taken up by the intestinal microflora.
Of special concern is the possible transfer of genes conferring
antibiotic resistance, leading to an increase in mammalian pathogens
that are resistant to antimicrobial agents" (p. 204). The objective
of this study was to "assess transgene survival in the small intestine
of human volunteers fed GM soya" (p. 204). Some patients had normal
bowels while others had ileostomies, in which the contents of the small
intestine are diverted from the body to an external bag.
Results of This Study:
-
When a meal containing GM soybeans was fed to seven people with
ileostomies, the CP4 EPSPS transgene was detected in the intestinal
excreta of every patient. Nontransgenic soybean DNA (the Le1
gene) was recovered at the same rate, so the transgene DNA was not more
persisent than usual.
-
In contrast, the CP4 EPSPS transgene could not be detected in the feces
of 12 patients with normal bowels after the GM soybean meal. "Thus,
although the epsps transgene can survive passage through the small
bowel of ileostomists, it is completely degraded in the large intestine"
(p. 205).
-
Prior to the feeding experiment, samples of intestinal excreta
from the ileostomists were analyzed for the presence of the
CP4 EPSPS transgene, but it was not detected. Upon culturing the excreta
to multiply the intestinal flora, however, the CP4 EPSPS transgene
was detected in three people. "The observation that the transgene
fragment was detected only when the microbial population had been
amplified indicates that the DNA was stably maintained in the [intestinal]
bacteria" (p. 207). "Gene transfer from GM soya to the intestinal
microflora appears to have occurred before the feeding experiment"
(p. 207), presumably because those people had already been eating the
soya.
-
"No microbes containing the transgene could be cultured from the feces
of humans with an intact gastrointestinal tract. This may indicate
that the bacteria containing the GM soya transgene were viable only
in the small bowel and do not survive in the large bowel" (p. 207).
Source:
Netherwood, T., S. M. Martin-Orue, A. G. O'Donnell, S. Gockling et al.
(2004). "Assessing the Survival of Transgenic Plant DNA in the Human
Gastrointestinal Tract," Nature Biotechnology vol. 22, pp. 204-9.
Author Affiliations:
University of Newcastle upon Tyne, UK.
Funding:
Food Standards Agency.
Product Status:
GM soybeans have been grown commercially in the U.S. since
1996 and currently constitute over 90% of the U.S. soybean crop.
Copyright 2009 The Nature
Institute.
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