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Hazards of Antibiotic Resistance Genes in GE Foods

From The September 2000 Issue of
Natural Foods Merchandiser
Health Threats Loom Over GMO Foods
Debate

Included as a Marker, Antibiotic Resistance Bred into Crops has Disastrous
Potential by Marty Traynor

Genetically modified genes in food crops can jump from one species to
another and can cause bacteria in the new host to mutate, according to a
zoologist working in Germany. His four-year study suggests that genetically
modified plants can contaminate bacteria in species that eat the plants.

Professor Hans-Heinrich Kaatz of the Institute for Bee Research at the
University of Jena found that genes used to modify oilseed rape (canola) were
transferred to bacteria in the guts of bees. He experimented with honey bees
and GM oilseed rape, which had been modified to resist a specific herbicide;
he removed oilseed rape pollen from legs of bees and fed the pollen to young
bees. When he examined the intestines of the young bees he found that some
carried the gene that resisted the herbicide.

Why are scientists concerned about genetic traits jumping species? Because
one of the genes used in genetic engineering by agricultural-sciences companies
is a gene resistant to antibiotics used as a marker--something like a genetic sticker
on fruit that can't be removed. That sticker is used to identify cells that took on
the new trait and to prevent theft of genetically modified seeds.

And if that resistance transfers to the humans who eat the products...

Well, the implications have some scientists worried.

"The spread of antibiotic resistance is the main threat from gene transfer from
GM crops," said Joe Cummins, Ph.D., professor emeritus of genetics at the
University of Western Ontario, Canada. "I have found that the antibiotics
used in GM crops are used in surgery and to treat a number of diseases."

But why are antibiotic-resistant genes used in this process? And how does
the process of genetic modification work?

Explanations from the biotechnology industry say that the process is one
of transferring a gene from an organism that has a desired trait into one that
lacks that trait.

But it's not that straightforward.

To take a gene from a bacterium, virus or animal that would never normally
crossbreed with the target plant, biotechnologists have to do more than just
insert the desired gene. A package of genes from bacteria, viruses and the
gene from the donating organism is built, according to ecologist Susan Borowitz,
writing for Terrain, the magazine of the Berkeley Ecology Center. The genes from
the bacteria and viruses serve two functions: They break down barriers between
species and they make sure the desired gene can be identified.

"Scientistas," Borowitz writes, "have to build a tool to trick plant cells into
accepting and incorporating genes from unrelated species." The tool includes
a "promoter," virtually always a gene from the Cauliflower Mosaic Virus, to
allow the new genes to work within the host organism. Organisms normally
repress, or "silence," new genes: The presence of the Cauliflower Mosaic Virus
makes this defense less effective. Geneticist Cummins said he fears this promoter
gene could recombine with other genes (bacteria and dormant viruses) to create
new pathogens that could be harmful or lethal to plants, animals or people.

An antibiotic-resistant gene is also added to the mix as a marker. This gene
will allow biotechnologists to identify the cells in which the transfer has been
successful. "The foreign DNA segment does not take hold in every cell, only
in a fraction of them," said Richard Wolfson, Ph.D. "To determine in which of
the cells the DNA has taken hold, researchers pour antibiotics into the cells.
The cells that do not die are the ones that the [foreign] DNA has been
incorporated into." The problem, Wolfson said, is that antibiotic-resistant genes
could transfer to pathogens. "They could become antibiotic resistant," he said,
"and this could produce diseases that can't be controlled by antibiotics."

The gene package is inserted into the plant in one of two ways.

One is through the use of gene carriers or vectors. The vectors made from
viruses or genetic parasites have "a talent for breaking into cells and
ingratiating into the cells' own genetic material, making cells express the genes
that are smuggled in," ecologist Borowitz wrote. The vector used most often,
T DNA, is the tumor-inducing plasmid of the soil bacterium, Agrobacterium.
It can invade a target cell and insert new genetic material into the plant's genome.

A second method of inserting genes is used for grass-like plants (corn and
other grains). Biotechnologists use gene guns armed with microscopic gold
or tungsten particles that are covered with DNA. The particles are then shot
directly into plant tissues. Scientists opposed to genetic modification of crops
warn that both processes can cause problems: The T DNA can affect other
cells while the gene gun can insert multiple copies of the new genetic code in the
plant with unpredictable results.

"The problem I see," said Cummins, "is that the ag people [understand] this
[process] theoretically, but they don't take it very seriously. They tend to rush
these preparations to release. They're not very imaginative in thinking about
the side effects in what they are doing."

Cummins, who reviews research published by biotech companies, has many
reservations about the safety of genetically modified crops. "Their practice of
science is a peculiar one," he said. The large biotechnology companies can present
research to the USDA and most of it is accepted in the United States and "rubber
stamped" in Canada. He paused and said, "They say they feel in their guts the
science is safe." He laughed and added, "What they feel in their guts is big bucks."

When the science is questioned, Cummins said he always gets the same answer.
"They always say 'The experiments haven't been done.' But who's going to do it?
The funding isn't there. Experiments need to be done in a university setting, and
done in microbial genetics--but most funding there comes from biotechnology."

For more information about the genetic modification of plants and other organisms:

Genetic Engineering: Dream or Nightmare? Mae-Wan Ho, Continuum, 1999

Unnatural Harvest, Ingeborg Boyens, Doubleday, 1999 www.i-sis.org

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