Bacteria Can Replace Lanthanides with Actinides To Sustain Their Metabolism
Bacteria that feed on methanol are able to grow on certain rare earth
elements as well as their radioactive relatives. These findings suggest
a possible role for such bacteria in the decontamination of areas where
actinides are spilled, or in the separation of lanthanides and
actinides for analytical or preparative purposes, according to a study
published in the journal Angewandte Chemie.
© Wiley-VCH, re-use with credit to 'Angewandte Chemie' and a link to the original article.
Lanthanides belong to the rare earth elements widely used in
electronics and energy technologies. With one exception, they are not
radioactive, they are abundant in the earth's crust, and some
lanthanides such as lanthanum and neodymium even play a crucial role in
bacterial metabolism. Actinides, which include uranium and plutonium,
are their heavy, radioactive counterparts, most of which are not found
naturally on earth. Now, Lena Daumann from Ludwig-Maximilians-University
Munich, Germany, and her international interdisciplinary team have
discovered that some actinides can replace essential lanthanides in the
metabolism of methylotrophic bacteria.
Methylotrophic bacteria, so-called as they use methanol as their
energy source, contain lanthanides in their methanol-oxidizing enzyme.
The researchers observed that these bacteria could also take up actinide
ions into this enzyme, using them for methanol metabolism in the same
way as they would use lanthanides. This observation was particularly
valid when the actinide ions were the same size and had the same stable
+III oxidation states as the corresponding lanthanides. The bacteria
even preferred americium and curium as actinides over some lanthanides
when presented with a mixture of lanthanides and actinides, the
researchers reported.
Americium and curium showed a stable +III oxidation state, which
appeared to be particularly important. “When we used plutonium, which is
known to have higher oxidation states, our bacteria did not grow, nor
did the isolated enzymes work with it either,” Daumann says. This
knowledge will be useful for future applications. The team plans to
explore the ability of the bacteria to extract actinides from
radioactive waste or to separate out specific elements from mixtures.
Actinides such as plutonium, americium, and curium can be generated
in nuclear reactors and are used in research, the nuclear industry, and
many other technologies. Americium is even a source of ionizing
radiation in commercial smoke detectors. However, actinides are highly
radioactive and hazardous elements, which have to be handled with great
care at special facilities. Spillages of radioactive substances are
always of great concern. Dauman proposes “putting these bacteria to use
to help clean up radioactive spills,” as a possible future application.
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About the Author
Lena Daumann is a
Professor at the Chemistry Department at Ludwig-Maximilians-Universität
München, Munich, Germany. Using model complexes, kinetic studies, and
spectroscopic techniques, her interdisciplinary research group
elucidates the mechanisms of action of lanthanides in
lanthanide-dependent bacteria and enzymes.
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