Forget
ancient maps and metal detectors. Those seeking hidden gold might do well to
add bacteria to their toolbox. The bacterium Delftia acidovorans secretes a
molecule that binds to dissolved gold and turns it into shiny, solid gold,
scientists have discovered.
The
bacterium — and perhaps others like it — might one day process gold at mining
sites or create gold nanoparticles with desirable properties, says
geomicrobiologist Frank Reith, a
research fellow at the University of Adelaide in Australia.
In 2006
Reith and his colleagues reported finding biofilms of bacteria growing on solid
gold grains in soil. Some of these microbial species precipitate gold from
solution, Reith and others found.
Now another
team reports how D. acidovorans performs its version of this trick: It secretes
a protein snippet that snatches up dissolved gold, forming metallic gold.
Nathan Magarvey of McMaster University in Canada and colleagues report the
finding online February 3 in Nature Chemical Biology.
The
bacterium’s gold-extracting technique is unusual, says geomicrobiologist Jim
Fredrickson of Pacific Northwest National Laboratory in Richland, Wash.
Dissolved gold is toxic to many bacteria, but passing electrons to the
dissolved element converts it to its metallic, innocuous form. Another
gold-altering microbe, Cupriavidus metallidurans, does the conversion inside
its cells. The molecule that D. acidovorans secretes renders gold solid and
inert.
“Somehow
it’s sensing the gold and protecting itself,” says Fredrickson, who was not
involved with the study.
Magarvey
and his colleagues have named the secreted compound delftibactin. They found
that delftibactin is similar to compounds that bacteria, fungi and some plants
use to extract iron and other metals from solution. Perhaps as it was evolving,
D. acidovorans co-opted the compound, enabling it to live in the company of
gold, Magarvey says.
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