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[SANET-MG] Wisconsin release of bacterial pathogens with antibiotic resistance genes
The closing date for public comments is rapidly approaching. This is one
chance to say keep GM microbes out of Organic Food Crops!
Field-testing Bacterial Pathogens with Antibiotic Resistance Genes
Prof. Joe Cummins objects on behalf of Independent Science Panel, so
should you
The University of Wisconsin is preparing to release genetically modified
(GM) Erwinia carotovora bacteria containing antibiotic resistance marker
genes in environmental field tests. The United States department of
Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS)
has prepared a docket with background information on the release and
there is a public comment period ending 15 September 2005 [1]. The tests
are to be conducted at the University of Wisconsin Experiment Station
near Hancock, Wisconsin. The environmental release of bacterial strains
each containing a different antibiotic should be a matter of grave
concern and a strong public response is in order.
The purpose of the field trial seems to be simply experimental with no
potential commercial application of the genetically modified bacteria.
Erwinia carotovora causes a rot disease in potatoes. The experiment is
designed to test the fitness of bacteria that have had genes known to be
associated with pathogenesis that have been disrupted by inserting in
those genes the antibiotic resistance genes. The antibiotic resistance
genes not only eliminate the function of the pathogenesis gene but they
also serve as selectable markers to identify the modified bacteria. The
antibiotic resistance genes are precisely inserted into the target
pathogenesis gene by adding short DNA tails to the resistance genes that
are homologous to the target pathogenesis gene. The pathogenesis gene
targeted is hrp, which controls secretion of virulence proteins into the
host plant. Green fluorescence protein was inserted as a visual marker
to identify potatoes with the modified bacteria [2].
The field test involves four GM mutant strains, WPP60,WPP198, WPP195 and
WPP40. WPP60 was created by inserting the streptomycin/spectomycin genes
into the hrpC, while WPP98 had chloramphenicol resistance gene inserted
into hrpL. WPP195 was created by deleting the hrpN gene and inserting
the choramphenicol resistance gene in its place. WPP40 has the kanamycin
resistance gene inserted into the outD gene required for protein
secretion, so it cannot secrete plant cell-wall degrading enzymes.
Inserting antibiotic resistance genes into the hrp genes interferes with
pathogenesis. However, only strain WPP40 that inactivates the outD gene
is reduced in virulence in a direct assay, nevertheless, the researchers
decided to carry out the field experiment [2].
They claim that the field tests are not expected to impact agricultural
practice because “the test is solely for research purposes” even though
Erwinia carotovora affects potato, cucumber, capsicum, turnip, brussel
sprouts, carrots and celery, all of which are grown in the general area
of the test site. Because the antibiotic resistance genes are not being
selected by antibiotic application, they are not deemed to be a cause
for concern, according to the applicants. The proposal believes that the
antibiotic resistance genes cannot be transferred to bacteria affecting
humans; justifying that position by referring to the US Food and Drug
Administration’s judgment that antibiotic resistance is already
prevalent in bacteria affecting humans and in soil-borne bacteria. Even
though the soil is sandy and porous in the test site, the applicants
claim that the spread of the GM bacteria is not expected, nor has it
been tested for [2]. In general, the application focuses on the benefits
of the experiments and ignores any evidence that might delay the
experiment. Apart from the release of antibiotic resistance genes, the
most obvious question is why release so many strains that are
genetically modified as well as still virulent? That procedure provides
high risk with little or no benefit.
1
The belief expressed in the proposal, that GM Erwinia carotovora would
not transfer antibiotic resistance genes to other soil bacteria, is
inconsistent with the scientific literature. Horizontal gene transfer is
commonplace in Erwinia and Klebsiella and transfer could extend to
Salmonella, Shigella and E. coli [3]. The GM bacteria contaminating
surfaces of food crops may also transfer antibiotic resistance gene to
enteric bacteria when ingested by humans or animals. Bacteria phage were
found to transfer genes between Erwinia species [4]. Transposons capable
of mobilizing antibiotic resistance genes have been identified in
Erwinia carotovora [5]. There is thus clear evidence that Erwinia is
capable of moving resistance genes among soil Erwinia species, between
other soil bacterial species and among enteric bacteria.
A number of GM microbes bearing antibiotic resistance markers have been
released commercially in the United States, these include Sinorhizobium,
Agrobacterium and Psuedomonas [6]. Little effort appears to have been
made to monitor the consequences of these releases. Mae-Wan Ho has
discussed the hazards of horizontal gene transfer in some detail [7, 8].
The main problem with the proposed field test of GM Erwinia carotovara
is the failure to monitor the spread of the modified bacteria and the
horizontal spread of transgenes. The release of virulent GM Erwinia does
not appear to provide any benefit that would justify the risks of
spreading the antibiotic genes.
This article has been submitted to the US EPA on behalf of the
Independent Science Panel. Please add your support by registering your
opposition in the docket by referring to this article.
Reference
1. University of Wisconsin-Madison Availability of Environmental
Assessment for Field Tests of Genetically Engineered Erwinia carotovora
Agency Document Number APHIS-2005-0069-0001 Comment Period End Date
(mm/dd/yyyy): 09-12-2005
http://docket.epa.gov/edkfed/do/EDKStaffCollectionDetailView?objectId=0b0007d48094780b
2. USDA/APHIS Environmental Assessment in response to permit application
(05-097-01r) received from University of Wisconsin for field testing of
genetically engineered strains of bacterium, Erwinia carotovora subsp.
Carotovora 2005
http://docket.epa.gov/edkfed/do/EDKStaffAttachDownloadPDF?objectId=090007d48094780e
3 Mulec J, Starcic M and Zgur-Bertok D. F-like plasmid sequences in
enteric bacteria of diverse origin, with implication of horizontal
transfer and plasmid host range. Curr Microbiol. 2002, 44, 231-5.
4. Chatterjee AK, Ross LM, McEvoy JL and Thurn KK. pULB113, an
RP4::mini-Mu plasmid, mediates chromosomal mobilization and R-prime
formation in Erwinia amylovora, Erwinia chrysanthemi, and subspecies of
Erwinia carotovora. Appl Environ Microbiol. 1985, 50(1),1-9.
5. Kotoujansky A, Lemattre M and Boistard P. Utilization of a
thermosensitive episome bearing transposon TN10 to isolate Hfr donor
strains of Erwinia carotovora subsp. Chrysanthemi. J Bacteriol. 1982,
150(1),122-31.
6. Cummins J. GM microbes invade North America. Science in Society 2003,
19, 39.
2
7. Ho MW Horizontal gene transfer – The hidden hazards of genetic
engineering. ISIS Report http://www.i-sis.org.uk/full/HGTFull.php; also
Biotechnology Series, Third World Network, Penang 2001.
8. Ho MW Recent evidence confirms risks of horizontal gene transfer.
ISIS contribution to ACNFP/Food Standards Agency open meeting 2002
http://www.i-sis.org.uk/FSAopenmeeting.php
3
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