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Thursday, 23 March, 2000, 17:50 GMT
GM genes refuse to budge
test tubes
The tests still have some way to go
By environment correspondent Alex Kirby

Researchers in the United Kingdom are cautiously hopeful that at least one of the concerns about genetically-modified (GM) crops may prove unfounded.

The researchers, led by Dr John Heritage, a microbiologist at the University of Leeds, looked for evidence that a gene in a commercial variety of GM maize was being picked up and activated by bacteria.

The gene, called bla, confers resistance to ampicillin, a commonly used antibiotic. It is not active in the plants themselves, but the worry is that when the maize is fed to animals their gut bacteria could pick it up and make it active.

If it did leak in this way, it could confer the same resistance to ampicillin, and to related penicillin-like antibiotics, on life-threatening organisms.

Maize pest

The gene is in the maize because it was already on the plasmid - plasmids are loops of DNA routinely swapped by bacteria - which was used to modify the plant in the first place.

The maize was developed by the Swiss company Ciba-Geigy, now Novartis, to produce a bacterial toxin lethal to the European corn borer, a major maize pest.


john heritage
Dr John Heritage
The modification was carried out some years ago, and at the time nobody saw any reason for removing the bla gene from the plasmid.

Dr Heritage and his colleagues are only halfway through their government-funded project. Their work is featured in New Scientist magazine.

So far, their experiments to see whether bacteria pick up and activate bla have found no evidence that they do.

Dr Heritage, though, says their work still cannot exclude the possibility entirely.

One of the team's experiments involved seeking 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.

Evidence incomplete

In another, the researchers added pUC18, the bla-bearing plasmid used to produce the maize, to silage effluent, and to saliva and rumen fluid taken from sheep.

Dr Heritage said: "We haven't seen it taken up and activated by bacteria in the normal flora of the rumen, saliva or silage yet."


farmyard chicken
Chickens appear not to activate the gene
But he added a warning: "That doesn't mean there aren't conditions where it might be taken up and activated."

Dr Heritage plans now to test what happens to the bla gene when the maize is fed to sheep.

The maize in question is sold widely in the US, and in 1996 the European Commission cleared it for sale in the EU, though UK experts opposed the decision.

He said he was glad money had been spent investigating "what was always a speculative scenario. It now looks as though the risk is less than was originally thought."

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See also:

17 Mar 00 | Sci/Tech
GM trial sites unveiled
21 Mar 00 | Sci/Tech
France's GM veto ruled wrong
31 Jan 00 | Sci/Tech
No reliable test for GM-free food
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