“What he saw was a lacy pattern of tiny cylinders joined by thin rods. The cylinders were the same size as thePedomicrobium bacteria.

Now gold stops most bacteria dead in their tracks – with suffocation. It blocks up the tiny holes in the cell walls through which food comes in and wastes go out. But Pedomicrobium, has an unusual way of reproduction. Most bacteria make babies just by splitting into two separate cells. But Pedomicrobium reproduces by budding. It stretches out a narrow stalk which rises above the gilded cage closing around the parent bacteria. This narrow tube then opens up (at the end) to make a new bacteria. So new baby bacteria are continually being born just on the outside of an expanding ball of golden death. It’s a slow process – it takes over a year to ‘grow’ a gold grain roughly the thickness of a human hair (about 0.1 mm). It would take a long time to ‘grow’ a 70 kg nugget. (Maybe we could speed the process up, by genetically engineering the Pedomicrobium bacteria.)

There are similar lacy patterns in 2.8 billion-year-old South African gold, and in 220 million-year-old Chinese gold. Of course, when you melt the gold in a furnace, the carbon from the bacteria just vaporises into carbon dioxide, leaving behind pure gold.

The bacteria don’t actually ”make” the gold – they just attract gold that is already dissolved in the groundwater. Now we have absolutely no idea why these bacteria can purify gold to almost 24 carat purity…”