radio-active substances , bacteria - (Aug/01/2009 )

Hallo,

can a bacteria break down radio-active substances?

I have heard that bacteria were used to clean up polluted ground even readio-active ones.
But do the bacteria then become radio-active or not.

because if they do, then you simply shift the problem from the ground to the bacteria and I do not see what the point of that is.

any ideas?

Yes, the bacteria become radioactive, so, in a sense, you are right, they have just moved the problem. But there is great utility in concentrating the problem to a smaller volume. Concentration of rare metals is important -- this is why mining and smelting is used to make metals is important.

ok, but what about this then: article
they say here:

So if I read this, I really understand it as: they break down the radioactive substance so that its not radioactive anymore.

I am misinterpretating this then?

lyok on Aug 1 2009, 08:20 PM said:

They cannot break down radioactive compounds or elements and I'm quite sure they will never do this. In the text stands "....that might one day...", i.e. a pure guess. Radioactive substances are elements and no organism can change one chemical element into another, otherwise they would be little suns or tiny nuclear reactors.
These bacteria gain oxygen by releasing oxygen from metal oxides (here also from uranium oxides) for respiration, that's all. I.e. a chemical reaction called reduction. There are even micro-organisms that gain energy from radioactive decay, but even those cannot do it. For radioactive isotopes we have to wait for their own fast or slow decay...
The use of such bacteria would be, as written in the publication, to form insoluble compounds from liquid compounds. I.e. an immobilisation that they cannot spread more and e.g. pollute larger areas.

The article you cite includes alot of hype. The experiments were apparently performed in the lab and in pure culture so it remains to be seen if these will be effective in environmental application.

Here's the citation and abstract.

Appl Environ Microbiol. 2009 Jun;75(11):3641-7. Epub 2009 Apr 10. Links
Plutonium(V/VI) Reduction by the Metal-Reducing Bacteria Geobacter metallireducens GS-15 and Shewanella oneidensis MR-1.Icopini GA, Lack JG, Hersman LE, Neu MP, Boukhalfa H.
Chemistry Division, Los Alamos National Laboratory, New Mexico 87545, USA.

We examined the ability of the metal-reducing bacteria Geobacter metallireducens GS-15 and Shewanella oneidensis MR-1 to reduce Pu(VI) and Pu(V). Cell suspensions of both bacteria reduced oxidized Pu to Pu(IV). The rate of plutonium reduction was similar to the rate of U(VI) reduction obtained under similar conditions for each bacteria. The rates of Pu(VI) and U(VI) reduction by cell suspensions of S. oneidensis were slightly higher than the rates observed with G. metallireducens. The reduced form of Pu was characterized as aggregates of nanoparticulates of Pu(IV). Transmission electron microscopy images of the solids obtained from the cultures after the reduction of Pu(VI) and Pu(V) by S. oneidensis show that the Pu precipitates have a crystalline structure. The nanoparticulates of Pu(IV) were precipitated on the surface of or within the cell walls of the bacteria. The production of Pu(III) was not observed, which indicates that Pu(IV) was the stable form of reduced Pu under these experimental conditions. Experiments examining the ability of these bacteria to use Pu(VI) as a terminal electron acceptor for growth were inconclusive. A slight increase in cell density was observed for both G. metallireducens and S. oneidensis when Pu(VI) was provided as the sole electron acceptor; however, Pu(VI) concentrations decreased similarly in both the experimental and control cultures.

-GeorgeWolff-

Read the original article more carefully:

Since the bacteria can reduce chromium and uranium from the liquid phase to form insoluble compounds, they may be used to eliminate these two environmental pollutants from water.

The agency estimates that more than 2,500 billion liters of U.S. groundwater are contaminated with uranium as a consequence of nuclear weapons production.

The danger at such waste sites is that the toxic metals are soluble, and so can leak into the local water supply. But these bacteria naturally convert the metals into an insoluble form. Though the metals would remain in place , they would be stable solids instead of unstable liquids.

-HomeBrew-

All these are speculative in environmental application.

-GeorgeWolff-

I see,

its more a way to centralise or immobilise the radio-active waste so it can be contained safely or removed from water.

And its still in research really.

ok I got it.


However I have one more question.

What about this text (see attachement)

If I understand it correctly they use a bacterium to reducte the Hg +2 to Hg 0 wich is volatile.
Now is this Hg (2+) then radio-active? if so, then what about the Hg (0) ? Is this still radio-active.
Or has the bacterium become radio-active and the Hg (0) not?

Or is it simply that the Hg (0) i still radio-active, but because this is a very inert form, they can contain this safely and wait till the radio-activity is gone?



or do they simply want to remove the Hg from the waste, but is this Hg itself not radio-active?
(wich seems strange, since its part of the radio-active waste in general)

The proposed technique only changes the bioavailability and removal potential of the heavy metal - whether radioactive or not.

In other work, folks have suggested that radioactivity might serve as an energy source for melanized fungi (see the speculative article's citation and abstract below). If you actually look at the data behind it - the effect was pretty trivial.


Curr Opin Microbiol. 2008 Dec;11(6):525-31. Epub 2008 Oct 24. Links
Ionizing radiation: how fungi cope, adapt, and exploit with the help of melanin.Dadachova E, Casadevall A.
Department of Nuclear Medicine, Albert Einstein College of Medicine, 1695A Eastchester Road, Bronx, NY 10461, USA. edadacho@aecom.yu.edu

Life on Earth has always existed in the flux of ionizing radiation. However, fungi seem to interact with the ionizing radiation differently from other inhabitants of the Earth. Recent data show that melanized fungal species like those from Chernobyl's reactor respond to ionizing radiation with enhanced growth. Fungi colonize space stations and adapt morphologically to extreme conditions. Radiation exposure causes upregulation of many key genes, and an inducible microhomology-mediated recombination pathway could be a potential mechanism of adaptive evolution in eukaryotes. The discovery of melanized organisms in high radiation environments, the space stations, Antarctic mountains, and in the reactor cooling water combined with phenomenon of 'radiotropism' raises the tantalizing possibility that melanins have functions analogous to other energy harvesting pigments such as chlorophylls

So I see.
Its all about being able to change the substance or change the nature of the substance so it will not dissolve (or change it from liquid to solid or..)



That other thing you posted, I'll have to check that too I think
I was only reading or trying to read and understand how they could use bacteria.

It all seems a very hypothetical idea and very theoretical and in labs etc.
But maybe in the far future..
who knows.