Tuesday, February 28, 2006

Claimed damage to soil bacteria - DOESN'T HAPPEN!

Damage to soil bacteria non existent!

CONTINUATION OF A GMO PUNDIT DISCUSSION OF A PARTICULAR JIGMOD MEMORANDUM CLAIM:

"Damage to soil bacteria, notably through horizontal transfer: Heinemann J.A, Traavik T. (2004) Problems in monitoring horizontal gene transfer in field trials of transgenic plants. Nat. Biotechnol. 22, pp 1105-1109."

REBUTTAL COMMENT
GMO Pundit has carefully read this HT 2004 citation and it is grossly misleading: The JIGMOD claim is a clear missuse of science.

The "damage" doesn't exist. There is actually no explicit description of detected damage to soil bacteria in this paper.
The "problems" of its title refer to "analytical problems" in detection of extremely rare events. Eg difficuties in detection of trace genetic materials.

There is one necessary correction to a seriously misleading statement in the Heinemann Traavik 2004 paper (leading to a published corrigenda)

Quotes from the abstract of Heinemann and Traavik 2004:

(There is a Corrigenda (April 2005) associated with this Perspective.)
Problems in monitoring horizontal gene transfer in field trials of transgenic plants Jack A Heinemann & Terje Traavik

Summary: 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.

Corrigenda Nature Biotechnology 23, 488 (2005)
doi:10.1038/nbt0405-488d
Corrigendum: Problems in monitoring horizontal gene transfer in field trials of transgenic plants Jack A. Heinemann & Terje Traavik Nat. Biotechnol. 22, 1105−1109 (2004)

On page 1108, paragraph 1, line 7, reference 49 in the statement "B. thuringiensis has 'a significant history of mammalian pathogenicity'46 and is thus not irrelevant to food safety or other environmental issues" was inappropriately cited (reference 46 states: "Bt does not have a significant history of mammalian pathogenecity".) The text should have read that "B. thuringiensis belongs to a closely related clade of bacteria, which includes Bacillus cereus and Bacillus anthracis, and which has a significant history of mammalian pathogenicity1, 2 and is thus not irrelevant to food safety or other environmental issues. Members of this group are so closely related that they may be considered members of the same species, often differing only by the presence or absence of certain plasmids3, 4".

REFERENCES
1. Helgason, E., Caugant, D.A., Olsen, I. & Kolsto, A.-B. Genetic structure of population of Bacillus cereus and B. thuringiensis isolates associated with periodontitis and other human infections. J. Clin. Microbiol. 38, 1615−1622 (2000).
2. Økstad, O.A., Hegna, I., Lindbäck, T., Rishovd, A.-L. & Kolstø, A.-B. Genome organization is not conserved between Bacillus cereus and Bacillus subtilis. Microbiol. 145, 621−631 (1999).
3. Helgason, E. et al. Bacillus anthracis, Bacillus cereus, and Bacillus thuringiensis—one species on the basis of genetic evidence. Appl. Environ. Microbiol. 66, 2627−2630 (2000).
4. Hoffmaster, A.R. et al. Identification of anthrax toxin genes in a Bacillus cereus associated with an illness resembling inhalation anthrax. Proc. Natl. Acad. Sci. USA 101, 8449−8454 (2004).

Note also there was another related Perspective, taking a different theme, on gene movement published jointly with the HT 2004 paper.

Monitoring and modeling horizontal gene transfer
Kaare M Nielsen & Jeffrey P Townsend

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 there-fore 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 hypotheses tested.

Nature Biotechnology 22, 1110 - 1114 (2004)
Published online: 31 August 2004; | doi:10.1038/nbt1006

1 comment:

Ildiko Welsh said...

my comment will follow