GM Microbes Invade North America
Pastor Dale Morgan
GM Microbes Invade North America*
ISIS
While the attention of the world is focused on genetically modified (GM)
crops, GM microbes have been released for at least six years with little
or no public awareness or debate. Prof. Joe Cummins reports.
The full list of references for this article are posted on ISIS Members'
website.
A number of GM microbes are being widely deployed since their first
release six years ago.
Sinorhizobium meliloti is a bacterium added to soil or inoculated into
seeds to enhance nodule formation and nitrogen fixation in the roots of
legumes. It was released for commercial production in 1997.
The other commercial GM microbes are designated as bio-pesticides. These
include GM Agrobacterium radiobacter k1026, used to prevent crown gall
disease in fruit and vegetable plants, and Pseudomonas fluorescens
modified with a number of different Cry delta-endotoxin genes from
different subspecies of Bacillus thruingiensis (Bt). The modified P.
fluorescens cultures are killed by heat pasteurization and provides a
persistent biopesticide preparation that degrades much slower in
sunlight than Bt.
Neither the people selling nor those using the preparations are
necessarily aware that the microbes are genetically modified, however.
Even organic farmers may be using them inadvertently.
The legume symbiont, Sinorhizobium meliloti, is tremendously important
for fixing nitrogen from the air into plant roots and the soil. Legumes
signal to the bacterium by exuding flavonoids from their roots,
activating the expression of nodulation genes in the bacterium,
resulting in the production of Nod factors that regulate the formation
of nitrogen fixing root nodules [1]. The S. meliloti genome has been
fully sequenced. It is unusual in containing three chromosomes (or a
chromosome and two very large plasmids), all of them contributing to the
symbiosis with the plant roots [2]. The genetically modified commercial
strain (RMBPC-2) has genes added that regulate nitrogenase enzyme (for
nitrogen fixation) along with genes that increase the organic acid
delivered from the plant to the nodule bacterium. It also has the
antibiotic resistance marker genes for streptomycin and spectinomycin
[3]. The commercial release was permitted in spite of concerns about the
impact of the GM microbe on the environment.
Evidence supporting the initial concerns has accumulated but that has
not dampened the use of the GM microbe. For example, a recent review
reports that GM S. meliloti strains persisted in the soil for six years,
even in the absence of the legume hosts. Horizontal gene transfer to
other soil bacteria and microevolution of plasmids was observed [4].
Other studies showed that a soil micro arthropod ingested GM S.
meliloti, and a GM E. coli in the arthropod gut facilitated gene
transfer to a range of bacteria [5].
There is little doubt that the antibiotic resistance markers for
streptomycin and spectinomycin will be transferred to soil bacteria and
to a range of animal pathogens. For example, the resistance genes for
streptomycin could be observed to transfer from their insertion as
transgenes in plant chloroplast to infecting bacterium Actinobacter sp.
[6] when homologous gene sequences were present.
The antibiotics spectinomycin and streptomycin are used extensively in
human and animal medicine. Spectinomycin is used to treat human
gonorrhea [7] and bovine pneumonia [8]. Streptomycin is used to treat
human tuberculosis [9] and Meniere's disease [10] and as a pesticide on
fruits and vegetables [11]. Thus, the commercial release of GM
Sinorhizobium meliloti has resulted in the establishment of the GM
microbe in the soil in millions of acres of cropland, where it can
spread antibiotic resistance genes for antibiotics that are extensively
in use in medicine and agriculture.
Agrobacterium radiobacter k1026 [12] is a bio-pesticide derived from A.
radiobacter k84, a natural bacterium used to control the crown gall
disease of fruits and ornamental trees and shrubs. Crown gall disease is
due to the bacterium Agrobacterium tumefaciens that causes tumors to
form on the plant stems, and is the most common vector employed in plant
genetic engineering.
GM Agrobacterium radiobacter releases a chemical warfare agent
bacteriocin (agrocin) against A. tumefaciens. Bacteriocin is a novel
nucleic acid derivative that prevents the crown gall tumors from forming
in the infected plants. The GM A. radiobacter has an engineered deletion
in the genes controlling plasmid transfer so that the 'male' bacterium
cannot transfer its plasmid, but it can act as a 'female' to receive a
plasmid transfer. However, recent research suggests that retrotransfer
of genetic material can occur from 'female' recipient to 'male' donor
bacterium [13].
Pseudomonas flourescens strains modified with Cry delta endotoxin genes
from Bacillus thuringiensis are killed before being marketed [14]. The
killed GM bacteria are more persistent than are the conventionall B.
thuringiensis sprays. The main fallacy in the approval of these
biopesticides is to suppose that bacteria cannot enjoy sex (conjugation)
after death, they do.
Soil bacteria are also easily transformed with cell lysates (squashed
dead cells) and function in their genetically modified form in soil
microcosms [15]. P. fluorescens and A. tumefacians are both transformed
in soil [16]. Soil Pseudomonas and Actinobacter can also take up genes
from transgenic plants [17]. So, the combination of transgenic crops and
GM biopesticides can create genetic combinations capable of devastating
the soil microflora and microfauna.
In conclusion, GM microbes have begun to be ubiquitous invaders of the
North America ecosystem. This massive invasion took place with little or
no public awareness and input, and with very little monitoring of the
impact of the invasion. The environmental risk assessments of the
commercial microbes were rudimentary and frequently erroneous. We may
have a bio-weapons equivalent of a time bomb on our hands.