Bacteria That Can Eat Radioactive Waste Discovered
Tiny
single-cell organisms living underground could help with the problem of
nuclear waste disposal, according to a paper in the ISME (Multidisciplinary Journal of Microbial Ecology) Journal.
This is good news for Americans, since the Obama administration has
lost the Yucca Mountain nuclear waste repository application even more
often than the U.S. Internal Revenue Service has lost the emails showing
they targeted political opponents.
Bacteria with waste-eating
properties have been discovered before, but in relatively pristine
soils. This is the first time finding microbes that can survive in the
very harsh conditions expected in radioactive waste disposal sites.
The
disposal of our nuclear waste is very challenging, with very large
volumes destined for burial deep underground. The largest volume of
radioactive waste, termed "intermediate level" and comprising of 364,000
m3, are encased in concrete prior to disposal into
underground vaults. At some point, ground waters may reach these waste
materials and they will react with the cement and become highly
alkaline. This change drives a series of chemical reactions, triggering
the breakdown of the various "cellulose" based materials that are
present in these complex wastes.
The bacterium (inset) was found in soil samples
in the Peak District. Credit: University of Manchester
One
such product linked to these activities, isosaccharinic acid (ISA),
causes much concern as it can react with a wide range of radionuclides -
unstable and toxic elements that are formed during the production of
nuclear power and make up the radioactive component of nuclear waste. If
the ISA binds to radionuclides, such as uranium, then the radionuclides
will become far more soluble and more likely to flow out of the
underground vaults to surface environments, where they could enter
drinking water or the food chain. However, the researchers' new findings
indicate that microorganisms may prevent this becoming a problem.
Working
on soil samples from a highly alkaline industrial site in the Peak
District, which is not radioactive but does suffer from severe
contamination with highly alkaline lime kiln wastes, they discovered
specialist "extremophile" bacteria that thrive under the alkaline
conditions expected in cement-based radioactive waste. The organisms are
not only superbly adapted to live in the highly alkaline lime wastes,
but they can use the ISA as a source of food and energy under conditions
that mimic those expected in and around intermediate level rad-waste
disposal sites. For example, when there is no oxygen (a likely scenario
in underground disposal vaults) to help these bacteria "breath" and
break down the ISA, these simple single cell microorganisms are able to
switch their metabolism to breath using other chemicals in the water,
such as nitrate or iron.
The fascinating biological processes
that they use to support life under such extreme conditions are being
studied by the Manchester group, as well as the stabilizing effects of
these humble bacteria on radioactive waste. The ultimate aim of this
work is to improve our understanding of the safe disposal of radioactive
waste underground by studying the unusual diet of these hazardous waste
eating microbes.
One of the researchers, Professor Jonathan
Lloyd, in the University's School of Earth, Atmospheric and
Environmental Sciences, said, "We are very interested in these Peak
District microorganisms. Given that they must have evolved to thrive at
the highly alkaline lime-kiln site in only a few decades, it is highly
likely that similar bacteria will behave in the same way and adapt to
living off ISA in and around buried cement-based nuclear waste quite
quickly.
"Nuclear waste will remain buried deep underground for
many thousands of years so there is plenty of time for the bacteria to
become adapted. Our next step will be to see what impact they have on
radioactive materials. We expect them to help keep radioactive materials
fixed underground through their unusual dietary habits, and their
ability to naturally degrade ISA."
Citation:
Naji M Bassil, Nicholas Bryan, Jonathan R Lloyd, 'Microbial degradation
of isosaccharinic acid at high pH', The ISME Journal advance 25 July
2014 doi:10.1038/ismej.2014.125. Source: University of Manchester
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