Metal Eating Bacteria.
C.metalludurans is a hardy little bacterium that consumes toxic metals,
and excretes gold nuggets.
How and why it does so has never been fully understood.
Now scientists have peered into this microorganism and figured out that mechanism.
C.metalludurans lives in soils full of heavy metals,
which are toxic to most other microorganisms.
But this bacteria has evolved to thrive under these conditions.
Apart from toxic heavy metals, the living conditions is not bad.
There is enough hydrogen to conserve energy, and nearly no competition.
C.metalludrans needs copper to live.
In order to extract the trace element from the surroundings,
the bacteria converts it into a form, that is easier to import.
There are a few problems.
High levels of copper are toxic, and that’s not the only heavy metal in the soil.
Gold compounds are also imported into its body, through the same process.
The natural form of gold is pretty toxic to it, but its even more potent,
when mixed with copper.
To deal with the first problem, the bacteria has an enzyme called CupA,
that pumps out excess copper.
When gold and copper are both taken up, the bacteria switches off this enzyme,
and fires a different one.
This new enzyme converts the gold and copper back into the old, hard-to-digest forms,
effectively solving the second problem.
This assures that fewer copper and gold compounds enter the cellular interior.
The bacterium is poisoned less, and the enzyme that pumps out the copper,
can dispose the excess copper unimpeded.
Another consequence, the gold compounds that are difficult to absorb,
transforms in the outer area of the cell into harmless, tiny gold nuggets,
only a few nano meters in size.
Through this process C.metalludurans may be responsible,
for some of Earth’s natural secondary gold.
Primary gold refers to the ancient’s deposits form geologically,
while secondary gold is much younger.
It is closer to the surface and often found in nugget form.
This often the result of ground water, dissolving the primary gold,
and transporting it upwards.
Certain bacteria may also chew off tiny flakes of primary gold,
that then move towards the surface.
The bacteria then convert it into secondary gold.
Scientists say that further understanding of this cycle may potentially allow gold,
to be wrung out of less rich ores, without the need toxic chemicals like mercury.