Using Bacteria to Mine for Precious Metals

How to use bacteria to mine for gold!
30 July 2006

Interview with 

Dr Anna-Louise Reysenbach, Portland State University


Chris - Here's a discovery that could quite literally be worth its weight in gold. A US researcher called Anna-Louise Reysenbach from Portland State University has found a class of extreme bacteria that can thrive in acid and near-boiling water. These are so-called thermoacidophiles and they've been found in hydrothermal vents on the ocean floor and they might be able to help above ground. This is because they could help in the extraction of precious metals from the debris that's left over in mines.

Anna - Louise: At deep sea hydrothermal vents where the hydrothermal fluid, that very high temperature hot fluid that comes from deep within the Earth's crust, that fluid which has pH of about 3.5, when it mixes with the cold seawater it makes these beautiful chimneys, these chimney structures, these porous rocks, and it's been predicted that in those chimneys there are areas where there's low pH, and so you'd expect that there would be microbes that would live at these low pH environments, and yet nobody has every discovered a thermoacidophile, which is an organism that grows at low pH and at high temperature from deep sea vents.

Chris - Well, you've obviously succeeded, so how did you manage to recover these particular organisms and then culture them?

Anna - Louise: First of all the one thing I knew based on some molecular signal that a relative of one of these thermoacidophiles actually lived at these deep sea vents, and because of some geochemical modelling predicting that there were areas in these hydrothermal chimneys where there was low pH I decided that we should really try and look for microbes that can actually grow at these low pH's, and so we just tried to grow them under those conditions and voila, we got them.

Chris - How did you actually recover these ones?

Anna - Louise: Basically we used remotely operated vehicle called Jason II which is a little vehicle that's tethered to a ship and we can send it down, we have pilots that manipulate these hydraulic arms that then take samples for us at the bottom of the ocean, and then once in the lab, we just ground up the rocks, kept the rocks anaerobic, because this organism because this organism's anaerobic, it doesn't like oxygen, and we then inoculated bits of that rock into our acid media and then managed to get this little bug to grow.

Chris - What do you think the applications of them might be, because the mind boggles, you've got something which grows under extremely severe conditions?

Anna - Louise: One of the applications would be in bio-mining, where the mine tailings are often very acidic and there are organisms, thermoacidophiles actually from terrestrial hot springs that are used to remove some of the last bits of the precious metals, so this organism could potentially also be used for such an application.

Chris - And what are you going to do next? Will you be sending Jason back for some more samples or will you be focussing your attention on the one bug you have got so far?

Anna - Louise: I think we're going to focus, for the moment, on looking at the distribution of this organism at other deep sea vents, so we have some samples from many different deep sea vent environments and so we've been trying to isolate it from some of the other places around the world, for example the Indian Ocean, the Pacific Ocean, the East Pacific Ocean, this one came from the South West Pacific, so we're trying to look at the distribution and see if its relatives are similar, if they share the same characteristics of being acid loving, heat loving deep sea vent microbes.

Chris - Anna-Louise Reysenbach from Portland State University who's managed to recover the world's first example of a thermoacidophile from a deep-sea vent.


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