[iagi-net-l] The smallest gold-diggers in the world - bacteria found in Australian mines help gold grains to form

[Noel Pranoto]

The smallest gold-diggers in the world
Bacteria found in Australian mines help gold grains to form.

Richard Van Noorden

This close-up, taken with an scanning electron microscope and coloured
for effect, looks like a dead bacterium coated in gold.(c) Frank
ReithProspectors looking for gold nuggets have swarms of tiny helpers:
bugs that take up toxic gold complexes from the soil and spit out pure
gold on to the grains around them. Research published today provides
strong evidence that bacteria known to produce gold in the laboratory
do their trick in the wild too.

Impure gold, mixed with silver and copper, is found in the veins of
minerals such as quartz, sometimes in such low concentrations as to be
invisible. More obvious to the casual prospector are the highly
enriched 'secondary grains' or nuggets found in river beds and soil.
It is thought that these may be formed by weathering processes that
either leach out the silver and copper metals, or wash the gold into
solution so it can accumulate elsewhere.

Frank Reith of the Australian National University in Canberra and his
colleagues have shown that microbes play a role too.

Geologists in the field have seen bacterial structures on gold grains
before, and microbiologists in the laboratory have shown that many
types of bacteria will deposit gold and other metals from solution.
But the link between bacteria and gold deposits was tenuous. Now Reith
and his team have bridged the divide.

Selengkapnya di http://www.nature.com/news/2006/060710/full/060710-13.html

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