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Approved-By:  John/Laurel Hopwood <[log in to unmask]>
Message-ID:  <l03130309b38c3f63c498@[198.234.69.163]>
Date:         Tue, 15 Jun 1999 13:44:30 -0400
Reply-To: Biotech Forum <[log in to unmask]>
Sender: Biotech Forum <[log in to unmask]>
From: John/Laurel Hopwood <[log in to unmask]>
Subject:      Emerging resistance to Bt spliced crops
To: [log in to unmask]
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Donella Meadows is a professor who has written several op eds on ecology
issues.  The following is an abbreviated, what I assume to be, op ed.
from laurel

The Global Citizen  May 14, 1998
Donella H. Meadows
(Donella H. Meadows is an adjunct professor of environmental
studies at Dartmouth College.)


DON'T GET INTO EVOLUTIONARY RACES WITH SMALL CRITTERS

A type of salmonella, called DT104, has become resistant to five common
antibiotics. In 1980 antibiotic-resistant DT104 showed up in less than 1%
of samples tested at the CDC;  now it shows up in 34 percent.  Why?  Many
doctors and scientists, including an expert committee
of the WTO, assume it's because we slosh around antibiotics carelessly,
especially in animal feed. The ecological law being violated here is
natural selection. Expose salmonella to an occasional medicinal dose of
antibiotic, and you'll kill them.  Expose them every day to a slight dose,
you'll kill some.  The ones that survive will be the most naturally
resistant.  They will produce the next generation, which will be even more
resistant.  Keep using sublethal doses
of antibiotic, and you'll end up with resistant bacteria.   People who
understand natural selection have been trying to stop routine feeding of
antibiotics for years.

A bacterium called Bt normally hangs out in soil and on leaves waiting for
a bug to eat it.  Different strains of Bt infect different bugs, including
cabbage worms, corn earworms, and Colorado potato beetles.  In the bug's
gut the Bt multiplies happily, makes a toxin that kills
the bug, and releases millions of offspring to go infect other bugs.
Organic gardeners use Bt as a natural insect control.  It poisons nothing
but the insect that is its host.

Along comes Monsanto, snips out the bacterial gene that codes for the Bt
toxin. pastes it into the genes of potatoes, corn, cotton.  When a potato
beetle or cotton bollworm chomps a leaf, it ingests Bt toxin.

If you see this as a perfect scheme for creating resistant pests, you
understand the law of natural selection.  Instead of occasional exposure to
Bt toxin, the pest encounters it throughout the growing season.  Inside of
a lethal dose, it gets a low-level one -- Bt-spliced cotton kills only 60
to 90 percent of cotton bollworms.  The ones that survive breed the next
generation.
No one knows what will happen in nature if insect populations become
resistant to wild Bt.

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