Newsgroup: it.scienza.biologia
Titolo: bioremediation e Hg

Qualcuno sa se esiste una metodologia per la detossificazione dei terreni da
metalli pesanti, in particolare Hg++, che faccia uso di batteri?
Io so che un ceppo di Pseudomonas putida è in grado di ridurre il mercurio a
mercurio metalllico (meno tossico), solo che non ho trovato applicazioni su
larga scala di questa possibilità (che fa uso dell'operone mer, molto
diffuso in natura)...
Grazie
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dawe
http://digilander.libero.it/daweonline

certo che si: 
 
  Microbial mercury mop
Eleanor Lawrence reports on a new strain of bacteria genetically
engineered to clean up soil and water contaminated by toxic radioactive
waste.
5 January 2000 
ELEANOR LAWRENCE
Radiation-resistant bacteria that can dispose of heavy metals are being
developed to help clean up soil and water contaminated by toxic
radioactive waste. Researchers have announced in the journal Nature
Biotechnology1 that they have constructed a version of the highly
radiation-resistant bacterium Deinococcus radiodurans that converts the
toxic mercury in such wastes to a less toxic form.
The United States has a major pollution problem with waste from its
nuclear weapons manufacturing programme. From 1945 until the 1980s, around
three million cubic metres of radioactive waste was disposed of by burying
it in the ground. Leakage of the buried waste at the 3,000 disposal sites
has contaminated surrounding soil and groundwater with radioactive
uranium-235, heavy metals like mercury and toxic organic solvents such as
toluene. 
This lethal mix now affects 75 million cubic metres of soil and two
billion litres of groundwater, and the cost of cleaning it up using purely
physico-chemical technology is estimated at around &dollar;265 billion. So
the search is on for less expensive ways of detoxifying the contaminated
ground.
One of these could be bioremediation. This is the use of living organisms,
usually bacteria or plants, which can break down the pollutants to use as
nutrients, or convert them into some less harmful form. The problem with
radioactive waste, however, is that most living organisms are highly
sensitive to radiation, which kills cells and damages DNA.
Enter Deinococcus, the most radiation-resistant organism known to man.
This astounding bacterium grows happily in levels of radioactivity of 60
grays (Gy) per hour -- about ten times the lethal dose for a human --
which is well above those in the waste. It is also quite tolerant of
organic solvents.
But Deinococcus does not like mercury, and this, radioactivity apart, is
one of the most problematic of the pollutants. In the radioactive waste,
mercury occurs in a highly toxic ionic form, 'Hg(II)'. Hassan Brim of the
Uniformed Services University of the Health Sciences at Bethesda,
Maryland, and colleagues have genetically engineered a suite of
mercury-handling genes into Deinococcus, which enable it to convert the
Hg(II) into less toxic elemental mercury (Hg), which is volatile and so
can disperse, and is also chemically almost inert. 
The genes come from the biotechnologist's friend, the bacterium
Escherichia coli, which perhaps surprisingly for a bacterium that lives in
the hospitable environment of the human gut can detoxify ionic mercury.
The Bethesda team found that they could combine the mercury-detoxifying
genes with specialized toluene-degrading genes taken from the harmless
soil bacterium Pseudomonas putida. The end result is a strain of
Deinococcus that converts mercury, breaks down toluene to use as a source
of carbon and energy, and does all this while thriving at radiation levels
that no other organism can resist.
 
 
References
Brim, H., McFarlan, S. C., Fredrickson, J. K., Minton, K. W., Zhai, M.,
Wackett, L. P. & Daly, M. J. Engineering Deinococcus radiodurans for metal
remediation in radioactive mixed waste environments Nature Biotechnology 
 
 
 
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Dell'uso di D. radiourans sapevo, il problema è che non si può, almeno in
Italia, spargere MOGM nell'ambiente, anche se per un nobile scopo. In ogni
caso grazie per esserti interessato
dawe