8-Misc: 5-day-experiment sufficient for green light for antibiotica resistance genes?
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- Date: Wed, 29 Mar 2000 10:30:18 +0200
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----------------------------- GENET-news -----------------------------
TITLE: So far so good
SOURCE: New Scientist, by Andy Coghlan
DATE: March 25, 2000
-------------------- archive: http://www.gene.ch/ --------------------
Dear GENET-news readers,
below reported results are a perfect proof for the hypothesis that
the appropriate results but not the methodological standard of risk
assessment experiments is used by GE-proponents to decide whether
"sound science" had been applied or not. Imagine what would have
happened if John Heritage and his colleagues discovered hints for a
gene transfer in their experiments. They would have been immediatelly
accused of premature announcements: "The government-funded project is
only halfway through and the researchers have yet to publish their
results in full." There method would have been declared as completely
insufficient: "Heritage looked for evidence that gut bacteria from
chickens had accepted and activated the bla gene, after the birds had
been fed the GM maize for five days."
I am looking forward which scientific journal with which editors is
going to give these experiments the status of a peer-reviewed paper.
So far so good
For the moment, the gene genie is staying in its bottle
ONE of the most convincing arguments levelled against genetically
modified crops is that the various genes in them that confer
resistance to antibiotics will spread into the environment,
eventually making life-threatening bacteria resistant to those drugs.
But such doomsday scenarios look less convincing this week, as
British researchers report having tried and failed to get various
bacteria to take up such a gene from a commercial variety of GM maize.
John Heritage and his colleagues at the University of Leeds presented
their results in Scarborough at a meeting of the British Society of
Animal Science. The government-funded project is only halfway through
and the researchers have yet to publish their results in full. But
they have so far drawn a blank in experiments to see if bacteria pick
up and activate bla, a gene in GM maize which confers resistance to
ampicillin, a commonly used antibiotic. The researchers caution,
however, that they still can't rule out the scenario altogether.
"It's encouraging that a reputable scientist has studied the transfer
of a gene from GM maize to bacteria to gain actual data, rather than
extending speculations that such an event might occur," says Charles
Arntzen, president of the Boyce Thompson Institute for Plant Research
in Ithaca, New York.
Developed by the Swiss company Ciba-Geigy, now Novartis, the maize is
engineered to produce a bacterial toxin lethal to the European corn
borer, a major pest of maize. Unlike other GM crops, it also contains
the bla gene against ampicillin. The gene is not active in the plant,
but the worry is that gut bacteria might pick it up and activate it
when the maize is fed to animals.
Once in the environment, the bacteria might spread the same gene to
hospitals, making life-threatening bugs resistant to ampicillin and
to related penicillin-like antibiotics. Despite the fact that the bla
gene is already abundant in bacteria through medical overuse of
ampicillin, opponents of GM foods fear that the maize would
exacerbate the existing problem.
Novartis sells the maize widely in the US, and in 1996 the European
Commission cleared it for sale in Europe, despite opposition from
British experts (New Scientist, 4 May 1996, p 7). But, two years
later, France's highest court banned the sale and cultivation of the
maize (New Scientist, 3 October 1998, p 5).
In his experiments, Heritage looked for evidence that gut bacteria
from chickens had accepted and activated the bla gene, after the
birds had been fed the GM maize for five days. Heritage even served
up the gene "on a plate" in plasmids, promiscuous loops of DNA
routinely swapped by bacteria. He added pUC18, the bla-bearing
plasmid used to produce the maize, to silage effluent and to saliva
and rumen fluid taken from sheep. "We haven't seen it taken up and
activated by bacteria in the normal flora of the rumen, saliva or
silage yet," he says.
But these negative findings aren't the end of the story, Heritage
warns. "That doesn't mean there aren't conditions where it might be
taken up and activated." Next, he plans to test the fate of the bla
gene when the maize is fed to sheep. "I'm glad [the government] spent
money investigating what was always a speculative scenario," says
Derek Burke, former chair of the British committee that recommended
Europe reject the maize. "It now looks as though the risk is less
than was originally thought," he says.
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