[permaculture] [Fwd: Re: [SANET-MG] Honeybee Colony Collapse Disorder may be caused by GMO Bt genes]
Lawrence F. London, Jr.
lfl at intrex.net
Fri Apr 6 00:47:33 EDT 2007
Horizontal Gene Transfer is between species, which is still in many
place thought impossible. It's happening, a lot . . .
Gene Ecology Guide to: Measuring Horizontal Gene Transfer
THIRD WORLD NETWORK BIOSAFETY INFORMATION SERVICE
6 September 2004
Dear Friends and colleagues,
Re: Papers on horizontal gene transfer point to flaws in monitoring
Two papers recently published in Nature Biotechnology indicate that current methods for monitoring horizontal gene
transfer (HGT) from transgenic crops to microorganisms are very problematic and too insensitive to detect HGT. As such,
even though monitoring efforts so far have largely failed to observe HGT events in the field or have deemed frequencies
too low or too rare to pose risks, this is clearly not the case.
The analysis by scientists from the New Zealand and Norwegian Institutes of Gene Ecology critiques contemporary HGT risk
assessment of transgenic crops. [Heinemann JA and Traavik T. “Problems in monitoring horizontal gene transfer in field
trials of transgenic plants” Nature Biotechnology 22, 1105-1109 (2004).] Using the evolution of penicillin-binding
proteins as an example, they show that current experimental limitations preclude measuring HGT with the sensitivity
necessary to dismiss any eventual environmental harm. A major implication is that HGT from transgenic crops to soil
microorganisms could still have an environmental impact at a frequency approximately a trillion times lower than what
the current risk assessment literature estimates the frequency to be. The analysis also suggests that current methods of
environmental sampling to capture genes or traits in a recombinant microbe are too insensitive for monitoring evolution
by HGT. Warning that HGT in microorganisms can have significant negative health and environmental consequences, such as
increased antibiotic resistance in some bacteria, they conclude: “Contrary to the conclusion of others, we believe that
new approaches to monitoring environmental scale applications of transgenic organisms are urgently needed.” They suggest
that such an approach would be a decision to consider the scientific uncertainty surrounding environmental applications
that introduce HGT risks (e.g. growing transgenic crops) and adjust the pace of their release to match developments in
scientists’ ability to monitor at relevant sensitivities, recognising that the technology of safety monitoring lags
behind that of genetic engineering.
The second paper, by scientists from the University of Tromso, Norway/Norwegian Institute of Gene Ecology, and from the
University of California, Berkeley, also finds flaws in HGT monitoring approaches, due to limited experimental
parameters. This paper by Nielsen KM and Townsend JP is on “Monitoring and modeling horizontal gene transfer” Nature
Biotechnology 22, 1110-1114 (2004). Using examples of studies that have attempted to monitor HGT through field or gut
sampling of bacteria exposed to transgenic plants, they show that real-time monitoring of HGT processes in complex
microbial communities has been severely limited by methodological constraints. Such attempts have also relied on weak
assumptions of the nature and scale of the process. The scientists state that realistic estimates of HGT rates are
rarely obtainable, nor are they predictive of the long-term effects of infrequent HGT events. They argue that risk
assessment should not focus on the frequency of HGT, but instead, since rare HGT events cannot be excluded, on the
effect of the horizontally transferred transgene on the survival of the bacterial transformant. Evidence shows that the
overwhelming majority of HGT events in nature are know to be eleterious to the bacterial transformant, as such it is
also likely that HGT events from transgenic plants would cause deleterious effects.
We reproduce below the abstracts of the two papers in Nature Biotechnology. The paper by Heinemann and Traavik can also
be found at http://www.nzige.canterbury.ac.nz/documents/Heinemann_Nat%20biotech_2004.pdf
A separate paper “Gene Ecology Guide to Measuring Horizontal Gene Transfer”, published by the New Zealand Institute of
Gene Ecology, is a summary critique of the effectiveness of attempts to measure HGT from transgenic plants to soil
microorganisms, and of extrapolations of those studies to conclude that the risks of HGT are low or can be ignored. As
such, claims that HGT has been studied and found to not be a significant risk are not justified. In such cases, the
absence of evidence of risk can easily be explained by extrapolations from the results of experiments that were simply
not suited for making a proper assessment of risk. The paper can be found at
With best wishes,
Lim Li Ching
Third World Network
121-S Jalan Utama
Email: twnet at po.jaring.my
Nature Biotechnology 22, 1105 - 1109 (2004)
Published online: 31 August 2004; | doi:10.1038/nbt1009
Problems in monitoring horizontal gene transfer in field trials of transgenic plants
Jack A Heinemann1, 2 & Terje Traavik2
1 New Zealand Institute of Gene Ecology, University of Canterbury, 8020, Private Bag 4800, Christchurch, New Zealand.
2 Norwegian Institute of Gene Ecology, POB 6418, N-9294 Science Park, Tromsø, Norway.
Correspondence should be addressed to Jack A Heinemann jack.heinemann at canterbury.ac.nz
Transgenic crops are approved for release in some countries, while many more countries are wrestling with the issue of
how to conduct risk assessments. Controls on field trials often include monitoring of horizontal gene transfer (HGT)
from crops to surrounding soil microorganisms. Our analysis of antibiotic-resistant bacteria and of the sensitivity of
current techniques for monitoring HGT from transgenic plants to soil microorganisms has two major implications for field
trial assessments of transgenic crops: first, HGT from transgenic plants to microbes could still have an environmental
impact at a frequency approximately a trillion times lower than the current risk assessment literature estimates the
frequency to be; and second, current methods of environmental sampling to capture genes or traits in a recombinant are
too insensitive for monitoring evolution by HGT. A model for HGT involving iterative short-patch events explains how HGT
can occur at high frequencies but be detected at extremely low frequencies.
Nature Biotechnology 22, 1110 - 1114 (2004)
Published online: 31 August 2004; | doi:10.1038/nbt1006
Monitoring and modeling horizontal gene transfer
Kaare M Nielsen1, 2 & Jeffrey P Townsend3
1 Department of Pharmacy, Faculty of Medicine, University of Tromsø, N9037 Tromsø, Norway.
2 Norwegian Institute of Gene Ecology, Research Park, N9294 Tromsø, Norway.
3 Department of Plant & Microbial Biology, University of California, Berkeley, California 947200-3102, USA.
Correspondence should be addressed to Kaare M Nielsen knielsen at farmasi.uit.no
Monitoring efforts have failed to identify horizontal gene transfer (HGT) events occurring from transgenic plants into
bacterial communities in soil or intestinal environments. The lack of such observations is frequently cited in biosafety
literature and by regulatory risk assessment. Our analysis of the sensitivity of current monitoring efforts shows that
studies to date have examined potential HGT events occurring in less than 2 g of sample material, when combined.
Moreover, a population genetic model predicts that rare bacterial transformants acquiring transgenes require years of
growth to out-compete wild-type bacteria. Time of sampling is therefore crucial to the useful implementation of
monitoring. A population genetic approach is advocated for elucidating the necessary sample sizes and times of sampling
for monitoring HGT into large bacterial populations. Major changes in current monitoring approaches are needed,
including explicit consideration of the population size of exposed bacteria, the bacterial generation time, the strength
of selection acting on the transgene-carrying bacteria, and the sample size necessary to verify or falsify the HGT
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