Bt corn and cotton are already being grown, and are for sale (unlabelled as
GMO's) in a store near you.
Actinomycetes are very interesting organisms, responsible for many of our
antibiotics. They live and act much like fungi, but are classified closer
to bacteria because they are prokaryotic. As far as the genetic
maleability of actinomycetes, I don't think it's much different from the
traditional Gram positive bacteria. Gram + bacteria are a bit less likely
to exchange genes because they seem unable or much less likely than Gram -
bacteria to undergo "conjugation," or a physical attachment for the purpose
of exchanging DNA.
The bad news is, YES, it should be possible for actinomycetes or bacteria
or even some fungi to take up genes from genetically modified plants,
because they can indeed incorporate DNA that is just floating around in the
soil. I would think that the presence of this gene in plant roots and
residues would make it possible for it to be released into the soil and
taken up in this way. This is called "transformation."
The good news is that extra genes are "expensive" to keep. Every new chunk
of DNA a cell takes in is one more thing it has to replicate in order to
reproduce. That requires energy and nutrients that are always in low
supply. Because of this, generally organisms will only keep DNA that is
useful. The fact that the Bt genes originally came from the bacterium
Bacillus thuringiensis tells us that at least for some organisms this is a
useful gene. Is it useful to many of them? Hard to say. If it was that
useful, it is likely that more of them would already have it, since it was
available in their neighbors for some time.
Also, I think transformation would be uncommon because DNA is good food.
Micro-organisms and their externally-released enzymes generally will just
treat the loose DNA as a foodsource, breaking it down into nucleotides and
sub-gene chunks that are not useful as new genetic material. It is
generally thought that transformation is more likely in clayey soils and in
tucked-away micro-crevices where DNA has been physically protected from all
the enzymes that are free in the soil.
It should also be easier for plasmids to survive than pieces of DNA
strands. Plasmids are a small circular piece of DNA, generally found in
bacteria but also in some fungi, esp. yeasts. Since they are a closed
package they are a little less susceptible to enzyme attack. Plasmids that
are transferred or taken up by a new microbe are also more likely to
survive this process and be utilized as genetic material rather than food
because they are an intact self-replicating set of genes rather than just a
chunk of potentially genetic stuff.
Last time I checked, plants did not have plasmids (although to be honest
I'm not sure what they're doing to them anymore), so I would think these
new genes are incorporated into the plants' normal genome. This way, it is
less likely that of the thousands of genes and "scrap" DNA, any individual
important gene would survive the death and decay of the plant material, and
ingestion by microbes, to subsequently be incorporated into their genomes
and actually be expressed.
This all does not answer the question of whether it happens. On an
individual "this plant's genes transferred to that microbe" basis, one
could safely say "No" this will not happen. On the larger scale of
trillions of corn plants and zillions of microbes, my answer would be
"maybe."
Lynne Carpenter-Boggs
Soil Microbiologist
USDA-ARS
803 Iowa Ave.
Morris, MN 56267
320-589-3411 x141
FAX 320-589-3787
lcboggs@mail.mrsars.usda.gov
______________________________ Reply Separator
_________________________________
Subject: FWD: Question re Actinomycetes
Author: Sheri C Huerd <huerd001@gold.tc.umn.edu> at Internet
Date: 10/4/1999 4:34 PM
I recently read that actinomycetes have some properties of both
bacteria and fungi. I would appreciate any of the molecular or soil
biologists among us to share their thoughts re what this might mean re the
likelihood of horizontal gene transfer to actinomycetes from exposure to
the biotech vectors/promoters/marker genes that get into the soil via
residues and/or root exudates.
I am wondering whether anyone has looked into this? Seems like a
good time given that GMO-corn expressing Bt through roots could be as
little as one season away (first approval could be in time for crop year
2002 according to DowAgroSciences).
chuck
Charles Benbrook CU FQPA site www.ecologic-ipm.com
Benbrook Consulting Services Ag BioTech InfoNet www.biotech-info.net
5085 Upper Pack River Road IPM site www.pmac.net
Sandpoint, Idaho 83864
208-263-5236 (Voice) 208-263-7342 (Fax)
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Sheri Huerd
411 Borlaug Hall
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University of Minnesota
St. Paul, MN 55108
612-625-1251
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Sheri Huerd
411 Borlaug Hall
1991 Upper Buford Circle
University of Minnesota
St. Paul, MN 55108
612-625-1251
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