Extreme life lurking underground

While teams continue to search for gold, others are looking for something quite different; life.
25 June 2019

Interview with 

Kay Kuloyo, University of the Free State,


Chris Smith interviews microbiologist Kay Kuloyo who is looking for extreme bacteria living kilometres underground in gold mines


Some of the water in the mine has been trapped down there for millions of years, seeping through cracks in the rocks. And while the team continues to search for gold, others are looking for something quite different; special forms of life. Scientists have found life in some bizarre and extreme conditions in the past like around deep sea vents, and in our continuing search for life on other planets, the extreme conditions inside our own planet may provide clues as to how life like this might survive? Chris Smith met with Kay Kuloyo, formerly from the University of the Free State and now at the University of Calgary, who is looking for life deep underground.

Kay - In 2010, there was a paper that was published about a worm found in fissure water in one of the mines. This is one of the biggest discoveries to date because before that we only found smaller life like bacteria and in this case it was a nematode, which is an even higher order microorganism. So that gave an indication that there could be different levels of life in extreme environments.

Chris - When we say extreme environments, where were these organisms found growing?

Kay - This was in a 2.3 kilometre depth mine in fissure water, probably about 30°. So when we talk about extreme environments we’re talking about in the deep mines where there is very little nutrients and the temperatures can go as high as 70°C.

Chris - So to find complicated life growing at those extreme temperatures, in very nutrient poor environments, says there's something pretty special about those sorts of organisms?

Kay - Yes. It means that these organisms have genes that can help them make the kind of food they need. In the absence of sunlight and other sources they can actually use the chemicals and the minerals in the elements to make their own food and survive these conditions.

Chris - How did they get here?

Kay - Well the theory is that over millions of years ago, as the water gradually seeped down into the surface of the Earth, and when you had seismic activities, and the water was going down some of these microorganisms came down with the water and they became trapped here for so long, and over time they have been able to adapt to the conditions here.

Chris - How do you know that's how it happened and that, for instance, they didn't just arrive with the last rainstorm washed in from above?

Kay - Okay. Well, we do isotope analysis of the waters for carbon-14 dating to determine the age of the water. That tells us that some of the water samples that we’ve taken here are millions of years old, and sometimes even up to billions of years old.

Chris - So if the water’s that old, the organisms must've been in it for at least that long?

Kay - Yes.

Chris - So why are you down this mine today?

Kay - We never pass a chance to take one or two samples because you never know what you find.

Chris - And how are you doing that?

Kay - We have sterile Falcon tubes with us that we always carry, and that's to grab samples. If we find a seepage in the rocks, we can take some of the water samples or if we find biofilm growing around the rocks, we take that and then we culture in the lab and see what's in there.

Chris - Because there’s some water dripping down over here, is this of interest?

Kay - We we think it might be fissure water, we need to ask the geologist to confirm that. But if we see water coming out of the rock surface like this it is properly old water that is seeping out. And then what you see on the surface of the rocks like the brown colour and the black colour, we think that’s microorganisms that are growing on the rock and also using the nutrients from the water to survive. So over time, they form a film on the rock of different colours; black or brown or white or pink, depending on the kind of nutrients that they are using. So for us, this is easy for us to collect and understand what the micro biodiversity is.

Chris - Do you have a lot of contamination from microorganisms brought here by us?

Kay - Yes. Because there's a lot of human activity, mining activity around here and especially the places where there's been a lot of development, then most times we find microorganisms that have come from human activities, even sometimes microorganisms like E. coli. We find them in these water samples so we have to be really careful what we say is originally from the mine and what's from the surface.

Chris - Shall we grab a sample?

Kay - Yes. Even very little water samples can yield a lot of information about the microorganisms. So I’m just going to scrape some of the brown colour. I don't know if you can smell a little bit of hydrogen sulphide?

Chris - It does smell a bit sulphurous, yeah.

Kay - I'm going to scrape some of the black colour because we think that could be sulphate reducing bacteria.

Chris - And why do you think the sulphur is important?

Kay - Because usually what you find in goldmine's is a lot of pyrites and sulphates as well and, you know, that's also associated with the gold.

Chris - So the bacteria are using the sulphates as a food source, because they're obviously not able to rely on energy coming from the sun, they have to get their food chemically?

Kay - From what's around them, yes. You find some of them use the sulphates, some use the iron as well and some use perhaps the nitrates.

Chris - What are the implications of this discovery?

Kay -  Well, because of the conditions that we are finding some of these microorganisms in. For instance, the ones we find in high sulphate areas in the goldmines we are able to use some of these microorganisms for cleaning things up, like acid mine drainage agents, things like that. Also use them for green technologies, taking away more chemicals and using biological agents.

Chris - As a vice president of the company has just pointed out, can you not discover a strain of organism that will eat gold and then poo it out in the right place and make their job a lot easier.

Kay - Well, that some of the research that we are doing where we have microorganisms that can bioaccumulate the gold, and then we can extract the gold from the microorganism. As one of them pointed out that in places where they cannot really reach or it's so dangerous is it possible for us to use microorganisms, that's the next level that we’re looking at. We do have some bench scale applications of this where we've seen it happen, with not just gold but copper and some other minerals, so taking it to bigger levels and really showing that it can work is what we're looking at now..

Chris - Can it be scaled industrially to match what these guys do with drills and diggers?

Kay - Well, that's going to take a lot of time. Microorganisms work at their own pace. Over time we can use it for small-scale applications but right now it cannot match what these guys are doing, but give us some time and we might be able to apply it to those processes.


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