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8-Misc: 5-day-experiment sufficient for green light for antibiotica resistance genes?



----------------------------- 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.

Yours,
Hartmut Meyer

                              *****


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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