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Unintended Effects of Genetic Manipulation
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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.

This document: http://www.natureinstitute.org/nontarget/reports/soybean_006.php

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