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Re: [SANET-MG] transgenic trees?



Hi John,
The scheme used in the Danbury mercury phytoremediation  using cotton
wood trees is,I understand,  to use two bacterial genes according to the
scheme below:MerB   R-CH2-Hg+ + H+to R-CH3 + Hg(II)
MerA  Hg(II) + NADPH to  Hg(0) + NADP+ + H+
In other words two bacterial genes are involved, Mer B takes methyl
mercury and converts it to ionic mercury. Mer A converts ionic mercury
to volatile elemental mercury. The elemental mercury  is released form
the tree leaves to the air. However, the elemental mercury  is
deposited  from air in snow and rain, when that mercury hits the soil or
water it is converted  back to ionic then to methyl mercury.
The bacterial genes prevent mercury poisoning in the tree,
If  mercury was trapped in the tree as a non-toxic complex (say with SH
rich protein) there would still be a problem getting rid of the tree as
fires or decay would release the mercury in gobs. The long term solution
is probably to bind the mercury to glass or to minerals which will hold
it for good.
Hope this helps, joe


John D'hondt wrote:

Sorry Joe but the whole concept has become even more mysterious after your
explanation.

What kind of a gene is it that makes a tree take up organic methyl mercury
from the soil without the tree getting poisoned in the process, then makes
the tree convert this mercury back to the atomic form so that it can be
evaporated and pollute a much wider area?

My reaction was mainly meant to question the necessity of using GM trees.
There are other plants and especially fungi that take up mercury and
sequester it. But right now I would be more inclined to question the wisdom
of deliberately spreading the mercury contamination. Are there data
available to establish the efficiency of this process?

Thanks,
John



Hi Cheryl and John,
Danbury Connecticut  is currently using  GM trees to remediate  a
heavily mercury polluted site. The GM trees grow well on the heavily
polluted soil but , contrary to what John indicated, they do not trap
the mercury but they do release it to the atmosphere. The promoters have
claimed that the mercury "safely" circulates in the atmosphere for years
than is deposited on earth in  in rainfall and snow. The released form
of mercury is elemental mercury rather than the toxic ionic or organic
forms. The problem, in reality, is that the elemental mercury is
deposited heavily in rain and snow maily  within a hundred mile radius
of the remediation site. It is like coal burning power plants and waste
sites in that both forms release mainly elemental mercury pollution.
When the elemental mercury  is deposited in soil or water bodies
microbes rapidly convert it into ionic and organic mercury. Organic
(methyl) mercury cause birth defects and nerve damage in humans and
bio-accumulates in fish and game. The US EPA seems schizophrenic in
supporting  both control off  atmosphere mercury emission and
remediation by gm trees.
There are GM trees on the "drawing board" that sequester mercury from
the soil but these trees will  release it in high amounts when the trees
are burned or decay naturally. The only true remediation of mercury may
be vitrification (adding to glass) or forming minerals  trapping the
mercury.
I hope this helps, sincerely, joe cummins

John D'hondt wrote:



Greetings to the list,
Could someone explain the relationship between transgenic trees and




mercury.




Thanks,
Cheryl Mulholland NC




Any reason to promote a transgenic anything is used Cheryl.
Trees take up some mercury when they grow in a mercury polluted site.
Maybe transgenic trees take up more mercury than ordinary trees but I


have


seen no convincing research for that.
Then for as long as the trees grow that mercury is for all practical


reasons


out of the environment. One could say that trees therefore have a


cleaning


function.
When they are burned at the end of their lives the hope is that the


mercury


spreads so thin that it won't matter.
But when one talks about it enough it begins to sound that only


transgenic


trees do something useful with mercury.
john



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