Differing views on the risks of genetically engineered foods
(March 25, 2002 – CropChoice news) – The following are two reports on a conference in New Zealand last week about the environmental
risks associated with horizontal gene transfer. The first report comes from Tremane Barr, an opponent of genetically engineered crops. The
second report comes from the Life Sciences Network, which supports agricultural biotechnology.
Full Steam Ahead on the GE Titanic and Damn the HGT Icebergs.
Report on ERMA Horizontal Gene Transfer Conference 20/03/02
By Tremane Barr
This was, or rather should have been, a landmark conference in the promotion of the debate on Horizontal Gene Transfer (HGT) and its risks
to the environment in Aotearoa/New Zealand. If there had been any doubt as to the relevance of the risks of HGT to our environment at the
beginning of the day they were well and truly dispelled by the end of the conference. It would not be unreasonable to say that by the end there
was a near unanimous consensus that HGT does occur and that it will eventually occur through GMOs when they are introduced into our
environment. However, such recognition of risk only seemed to enthuse the majority to carry on headlong into putting GMOs into the
environment in spite of the fact that there is neither the funding nor the technology available to even find out if, or where, a HGT risk is/has
But first to the detail of what is HGT,"Horizontal gene transfer refers to the transfer of genes or genetic material directly from one individual to
another by processes similar to infection. It is distinct from the normal process of vertical gene transfer - from parents to offspring - which occurs
in reproduction. Genetic engineering bypasses reproduction altogether by exploiting horizontal gene transfer, so genes can be transferred
between distant species that would never interbreed in nature."[i][i]
Dr Kaare Neilsen from Norway and lately Harvard University spent the morning outlining some of the details to do with HGT. some of the
more interesting details are:
- There are many different ways of HGT occurring.
- HGT is most likely where the transferred genes confer a selective advantage.
- Genes acquired from HGT via differently related species are less likely to be retained by the host.
- 17.6% of E.Coli genes are estimated to have been acquired by HGT at a rate of 1 gene per 50,000 years.
- However, it is extremely difficult to tell if a gene has been acquired by HGT.
- Screening for HGT from field trials is extremely difficult given current technology and lack of understanding of bacteria.
- Viruses increase likelihood of HGT.
Using bacteria as an example there are always 1-4% in any population who can be described as "mutators" i.e. those individuals that are more
susceptible than the rest to HGT. These mutators increase in number when a population is put under some sort of stress. This means that even
though the majority are unlikely to be susceptible to HGT the mutator part of the population can be likely be part of a HGT event. This means
that the mutator population needs to be studied more than the average in any population to look for HGT pollution. However, no such
technology exists to do this at this point in time. This is somewhat disturbing as a graph pointed out. Even though only a small number of
mutators may take on new genes via HGT if this results in a selective advantage then over time (and this could be a long time) this new
bacteria could out compete and take over the ecological space from the original species population.
In other words, even a small HGT event can in the long term lead to major changes in the bacteria population with all the potential negative
environmental effects that could come from that (or not as the case may be). For example, it does not matter how widely introduced a GMO
might be it only takes one HGT event in one place to start a long term process of completely changing a bacteria species and thus the
environment. Keeping in mind that this bacteria could easily transfer this gene back into a plant population, changing plants and the animals
and humans that eat it through further HGT. One interesting piece of disputed research is where claims have been made that 223 bacterial
genes have been found in the human genome presumably by HGT from bacteria. However, this is a disputed claim undergoing further research,
but potentially the implications of it if it is true could be quite important.
In theory, it only takes one HGT event via a mutator individual of a species to potentially change a whole species over the long term and thus
the environment, particularly if it confers a competitive advantage to the mutator that experiences HGT. Therefore, the idea that field trials are
safe because they are small is completely thrown out the window. Any GMO in the environment poses a risk of creating transgenic pollution
via HGT with potentially huge impacts in the long term.
HGT Transfer Frequency not Important
As was pointed out time and time again with GMOs in the environment the transfer frequency of HGT is not important because what we do
know is that HGT does occur naturally across species and therefore will occur with GMOs. With GMOs it is only a question of when and
where it will occur, and whether we will be able to detect it and if we do will it be in time to stop it from having a negative impact.
To put this in its context Jack Heinemann of Canterbury University pointed out that it is extremely difficult to simply detect HGT as at present
scientists are only aware of 10 million species of bacteria which is only 1% of the total number of bacteria species i.e. we don’t have clue
about the other 99%. On top of this of the species of bacteria that are known not all of them are able to be studied in the lab as they cannot be
cultured for analysis. Put in a global context bacteria hold as much carbon in them as all the plants on the planet and ten times the amount
of nitrogen than plants. While virus species out number bacteria by 10-100 times.
Horizontal Epigene Transfer
There is also another risk that comes from transgenic material that is not widely known about and this comes from horizontal epigene transfer.
Horizontal epigene transfer (HET) can come from molecules other than DNA called epigenes as they have long been known to carry heritable
information in the form of molecules which constitute epigenes.[ii][ii] Heinemann and others have shown horizontal epigene transfer occurs
between organisms where heritable changes continued long after the transferred molecule disappeared.[iii][iii] In other words transgenic
material in the form of epigenes can transmit heritable information that changes the DNA structure of a individual without actual transfer of a
whole gene as such. As I understand it at present we have no methods to detect this if HET did occur, though Heinemann through the NZ
Institute of Gene Ecology (NZIGE) is applying for funding to FRST to carry out research in this area which is supported by GE Free NZ and
Risk Assessment – Accepting Unknowability
Val Orchard of ESR gave an interesting talk on how unknowable the risks are from HGT and how it poses a fundamental challenge to the
science of risk assessment. The problems being we only know about known uncertainties and not those risks and unanticipated consequences
to which we have no possible idea of e.g. mad cow disease from prions. As Val pointed out the Titanic sunk in a sea that was 99% free of
icebergs. However, in spite of all the uncertainties and unknowable risks she introduced she was still supportive of this GE research going
ahead with GMOs in the environment.
Even Francis Wevers of the Life Science Network (LSN) had by this stage embraced the fact that HGT occurs naturally and will occur with
GMOs. Seen in its historical context this is a stunning admission as only last year the LSN were telling the Royal Commission (RCGM) that
HGT did not occur (so therefore it is not a problem), then as a result of testimony from independent scientists to the RCGM they changed their
story to one of HGT only ever happens very rarely (so therefore it is not a problem), to one of Wevers embracing the fact that HGT does
happen and will happen as a result of GMOs, so therefore because HGT does happen all the time it is still not a problem. This is the best PR
money can buy!
Genes Already in Environment so What’s the Risk?
Despite all the risks and dangers and inevitability of HGT the majority were quite happy, indeed insistent, that GE research and GMOs in the
environment should go ahead. This is not surprising considering the audience was mainly comprised of CRI GE scientists, government ministry
representatives and biotech industry people. However, the logic of their continued support for GE was based firstly on we have to do it to feed
a growing population, and secondly, the genes being transferred into GMOs exist in the environment anyway therefore if HGT is going to occur
with these genes then it will happen naturally anyway – so what's the problem.
I don’t want to carry on, but in addressing the first issue, "If one in seven people currently go to bed hungry, it is not because of an absolute
shortage of food, but because inequalities in political and economic power deny food to people. As long as access to food depends upon money,
and as long as poorer people are excluded from food markets or from land, significant numbers of people will be malnourished, hungry and
starving - whatever happens to the global food supply, and whatever happens to the number of people in the world.
Far from addressing these underlying structural causes of hunger, genetic engineering will do much to exacerbate them. Ensuring food security
worldwide requires an approach to agriculture that is, in almost every respect, the reverse of that being promoted by biotech companies and
their allies in government and regulatory authorities."[iv][iv]
"According to the United Nations food programme, there is enough food to feed the world one and a half times over. World cereal yields have
consistently outstripped population growth since 1980, but one billion are hungry. It is on account of corporate monopoly operating under the
globalised economy that the poor are getting poorer and hungrier. The new patents which are awarded on GM seeds (as well as other
life-forms and living processes) will intensify corporate monopoly by preventing farmers from saving and replanting seeds, which is what most
farmers still do in the Third World. Christian Aid, a major charity working with the Third World, concludes that GM crops will cause
unemployment, exacerbate Third World debt, threaten sustainable farming systems and damage the environment. It predicts famine for the
In addressing the second issue Dr Mae-Wan Ho of ISIS has dealt with the risks that accompany GMOs and their viruses used to create them
where she points out secondary horizontal transfer from transgenic material may spread the new genes and gene-constructs to unrelated
species. This can in principle, occur to all species that interact with the transgenic material, either directly or indirectly: microbes in the soil
and in other parts of the plants, worms, insects, arthropods, birds, small mammals and human beings.
Several factors make it more likely for the foreign genes that are introduced into GMO’s to take part in secondary horizontal gene transfer:
- The mechanisms that enable foreign genes to insert into the genome may enable them to jump out again, to re-insert at another site,
or to another genome.
- The unnatural gene constructs tend to be unstable, and hence prone to recombine with other genes.
- The metabolic stress on the host organism due to the continuous over-expression of the foreign genes may contribute to the
instability of the insert, as it is well-known that transposons are mobilized to jump out of genomes during conditions of stress, to multiply
and/or reinsert randomly at other sites resulting in many insertion-mutations.
- The foreign gene-constructs and the vectors into which they are spliced, are typically mosaics of DNA sequences from many
different species and their genetic parasites, and hence more prone to recombine with, and successfully transfer to, the genomes of many
The potential hazards from secondary horizontal gene transfer to unrelated species are as follows:
All of these risks from the inherent instability of GMOs and the viruses used to create them in the first place were glossed over by all the
scientists present. This made it exceedingly simple for people like Wevers to then accept that HGT does occur, but that it is not a risk.
This leads onto a major flaw of the conference being that apart from Neil McGregor all the other scientists were very pro-GE albeit preparing
to admit the risks from HGT. No mention was made of the scientists who presented material to the RCGM pointing out the very real danger of
HGT to our environment and health. In a review of research around the world on HGT all the work of Dr Ho and ISIS and others who point
out the risks of HGT were completely ignored. And as far as I am aware no one was even invited to give the other side of the HGT risk story.
- Generation of new viruses by recombination between the viral genes or promoters and viruses in recipient species and in the general
- Generation of new bacterial pathogens by recombination between the bacterial genes introduced and bacteria in recipient species and
in the general environment
- Spread of drug and antibiotic resistance marker genes among pathogens in recipient species and in the general environment
- Random, secondary insertion of genes into cells of recipient species, with harmful position and pleiotopic effects, including cancer
- Reactivation of dormant viruses that cause diseases by the Cauliflower Mosaic virus and other viral promoters in recipient species
- Multiplication of ecological impacts due to all the above.[vi][vi]
Risks to Organics
HGT presents a distinct risk not just to organics but our whole food supply. HGT from GMO material to bacteria cannot be contained even if
we could detect it had happened and acted in time. This could lead to bacteria spreading through soil that infects both organic and conventional
crops and livestock with transgenic and potentially harmful material. This could mean the end of organics as we know it, maybe and poses a
major threat to our "Clean, Green" agricultural image. Why do the government want to risk our main industry being flushed down the gurgler?
In light of the HSNO Bill which limits GMOs to field trials this now seems rather laughable given that HGT can occur at any time from any
transgenic material in the environment. The moratorium is a farce if we want to protect ourselves from the risk of transgenic pollution via HGT.
Apparently, there are even some on the Select Committee that are in so much denial about HGT that they consider it a creation of the RCGM.
This is a convenient way of trying to dismiss the issue, but as this conference proved HGT is a very real thing and it WILL occur with GMOs
in the environment, but the unknowns are as to its frequency of occurrence and impact. What we can assume is that with all these new viruses
engineered specifically to carry out HGT to make the GMOs in the first place the frequency of HGT occurring in the environment will only
increase once they are allowed into the environment.
This leaves the Greens in a huge dilemma having pledged themselves to vote for a Bill that will put GMOs into the environment with all the
risks of contamination that go with it, with HGT being just another of those risks. So much for the Greens policy for a GE Free NZ.
Lack of Research Funding
The scientists presenting all acknowledged the risk and that we need to do something about reducing the risk. However, they pointed out we
lack both the technology and the knowledge to even begin to understand the full implications of HGT and its impacts on our environment from
GMOs. They want to address this by receiving more funding by government for research in this area. However, even then it was accepted we
cannot know the unknowable, not that this will stop them.
In conclusion, the summary by Dr Wren Green of the IUCN was that HGT is not an uncommon occurrence with the frequency not really the
issue as we know it will occur sooner or later on an ongoing basis with GMOs in the environment. The real issue being what will be the
potential impact – will it be negative on a minor or major scale. As the concluding speaker pointed out normal risk assessment of deciding
how much pollution to put into the environment no longer applies because the HGT pollution will be alive and will be able to self replicate
and spread indefinitely.
It was acknowledged that the choice of whether or not to go ahead with taking this HGT risk comes down to ones beliefs and values system.
For the GE scientists there and Francis Wevers and LSN it is still full steam ahead on the GE Titanic and damn the HGT icebergs. For those
who want to keep Aotearoa/New Zealand GE free and avoid HGT risks the days of this dream are numbered and all that can be fought for
now is to try and limit the overall damage when it inevitably occurs.
[i][i] Report on horizontal gene transfer - Department of Public Prosecution versus Gavin Harte and others, New Ross, Ireland by Mae-Wan
Ho, March 22, 1999. Website: http://www.i-sis.org.uk/ireaff99.php
[ii][ii] Strohman, R. C. (1997). The coming Kuhnian revolution in biology. Nature Biotech. 15, 194-200
Weld, R., and Heinemann, J. A. (in press). Horizontal transfer of proteins between species: part of the big picture or just a genetic vignette?
In Horizontal Gene Transfer, C. I. Kado and M. Syvanen, eds. (London: Harcourts)
[iii][iii] Cogoni, C., and Macino, G. (2000). Post-transcriptional gene silencing across kingdoms. Curr. Opin. Genet. Develop. 10, 638-643.
Heinemann, J. A. (1999). Genetic evidence for protein transfer during bacterial conjugation. Plasmid 41, 240-247.
[iv][iv] The Corner House UK, "Ten Reasons Why GE Foods Will Not Feed the World". Website: http://www.purefood.org/ge/tenreasons.cfm
[v][v] See McCanceR.A. and Widdowson, E.M. (1991). The Composition of Foods, Fifth Edition, Royal Society of Chemistry, MAFF,
See Watkins, K. (1999). Free trade and farm fallacies. Third World Resurgence 100/101, 33-37.
Farm and Land in Farms, Final Estimates 1993-1997, USDA National Agricultural Statistics Service.
See Griffin, D. (1999). Agricultural globalization. A threat to food security? Third World Resurgence 100/101, 38-40. Farm Aid fact sheet:
The Farm Crisis Deepens, Cambridge, Mass, 1999.
Simms, A. (1999). Selling Suicide, farming, false promises and genetic engineering in developing countries, Christian Aid, London.
[vi][vi] www.i-sis.org.uk http://www.i-sis.org.uk
And now the press release about the seminar from the Life Sciences Network… http://www.lifesciencesnetwork.com/news-detail.asp?newsID=819
The Environmental Risk management Authority (ERMA) held a horizontal gene transfer (HGT) seminar in Wellington on Wednesday 20
March. The big questions of the day were; does horizontal gene transfer happen and if it does happen does it matter? The speakers concentrated
on the first question and we learnt about the mechanisms of horizontal gene transfer, particularly between bacteria. Unfortunately there was
little light thrown on the second question and the audience was left to form its own opinions what the consequences of horizontal gene transfer
On the face of it horizontal gene transfer seems to happen fairly frequently in that bacteria can, at times, take up genes from their surroundings
or from other bacteria. The speakers emphasized the big difference, however, between a bacteria taking up a piece of DNA and that DNA
ending up permanently in that bacteria1s genome.
Dr Kaare Nielsen from the Department of Microbiology in the Norwegian University of Tromso in Norway explained that DNA is more likely
to be taken up (by recipient bacteria) if:
a) the transferred DNA comes from a closely related bacteria;
b) the recipient bacteria has complementary sections of homology with the donor bacteria1s own DNA and
c) the fragment of DNA is the right length.
And then, even if a new piece of DNA is taken into a bacteria and incorporated into its genome the protein-product it encodes has to survive
transcriptional processing and produce a complete protein.
Both Dr Kaare and Dr Val Orchard from Environmental and Scientific Research (NZ) emphasised that even the production of a complete
protein is not enough to guarantee permanent incorporation of the new gene into a bacteria1s genome. The new protein has to he useful to the
bacteria because genes coding proteins that were neutral or disadvantageous would be lost from the genome over time. Selection pressure
(population genetics) would determine the utility of the new sequence and therefore its incorporation would ultimately depend on selective
Dr Orchard and Dr Neil Macgregor, a biological scientist at Massey University, highlighted the ubiquitous nature of bacteria and the multitude
of environments and large numbers in which they live. These factors make horizontal gene transfer, even if it happens very rarely, a near-
certain event. Any gene that gave bacteria an advantage could be quickly passed on to multiple offspring.
Dr Kaare said horizontal gene transfer was not a new phenomenon and since natural reservoirs of DNA already exist in the environment there
was little risk in shifting these genes around with genetic engineering. (Most transgenes at present come from soil bacteria.) He was concerned,
however, about incorporating completely novel genes into organisms in the future. Francis Wevers (LSN) reminded the audience that the risks
of any new technology need be considered in the context of any risks associated with existing technology. While the audience was left with a
better understanding of the process and likelihood of horizontal gene transfer there was no discussion on the consequences or magnitude of any
risks. Ironically Bas walker, the Chief Executive of ERMA, closed the day by talking about the need to ask questions in the right order. If this
does happen what would be the effects? Then we can go back and ask the more detailed questions.2 Unfortunately the seminar addressed the
detailed questions but not the most important question from a safety point of view – if horizontal gene transfer does happen what will be the effects.