Microbes make metallic copper

Bacteria that can turn mine waste into copper metal might be the answer to a looming copper crisis...
27 April 2021

Interview with 

Debora Rodrigues, University of Houston, Texas


A copper mining site, in Australia


65 years: that's how long we've got before one of the most valuable metals in the electrical, electronics and plumbing industries runs out. I'm talking, of course, about copper. But in the course of extracting this precious commodity, which is mined chiefly in the Americas, Africa and China, the environment often pays a very high price. Copper-rich, acidic mine waste in the form of dissolved copper compounds, like copper sulphate, flows into local rivers, lakes and the soil, where it's a potent poison that destroys the local ecology. But Debora Rodrigues, at the University of Houston, Texas, thinks she might have a solution. She went to look at what did live in areas hit by this pollution and was surprised to find flourishing communities of micro-organisms that have evolved to pick up these copper contaminants and turn them back into tiny fragments of harmless copper metal. It's early days, but this might be one way to clean up mine sites, and help to solve our looming copper crisis…

Debora - A lot of the copper mines that we have right now, they have a lot of leaching that comes out of it and they don't use. So we waste a lot of copper and then you generate a lot of contamination and pollution in the area as well. So here actually my back, I don't know if you can see, I have actually a lake that is contaminated with copper, and you see how blue it is.

Chris - Yes. I see. You've got your video up there and your backdrop is a very pretty colour, but not terribly pretty for things to live in, I gather.

Debora - No. And that kills a lot of life, fish, animals, and also it actually creates a huge impact in the environment. So what we are trying to do is actually obtain microorganisms from the environment. They can harvest this copper from the water, from soil, from different environments. And they accumulate inside their cells, and we can actually collect those microbes and take from them.

Chris - When you say they collect the copper, do they collect the dissolved form of copper and turn it back into metal then? Is that what you're saying?

Debora - That's right. That's exactly what I'm saying. They actually get the liquid part that dissolved one, and they transform it into a solid material.

Chris - Before you tell us how you discovered that they exist. Why do the microbes want to do that?

Debora - Well, like all living beings, we always try to make our environment better for survival. They are not different from us. They actually try to harvest the copper and make it into insoluble materials. So it makes it less toxic to them so they can survive in that environment.

Chris - So by being forced to live in a copper-rich, copper contaminated area, the microbes solve the problem by basically turning the copper into something which is less toxic, which is back into the metal form.

Debora - That's right.

Chris - Which, you know, funnily enough, we want.

Debora - Yes, we want that. Exactly.

Chris - How did these microbes come to your attention?

Debora - To be honest, we were not actually looking specifically for them. We were actually trying to understand the diversity of microbes in this environment, but I think that's the fun part of research is that sometimes we're looking for something, and we find something completely different that can be even better.

Chris - Do you know chemically how the microbes are recapturing this dissolved copper and turning it back into the metal in this way?

Debora - Yeah, actually, reducing copper sulfate in the water to produce copper, and they are using proteins. Like we all use proteins for digesting food. They use the proteins to digest the metal and transform it into something else.

Chris - I suppose then, there are two options here, aren't there? Either you could use the microbes as is to clean up wastewater, or you go and steal what it is that they have evolved to have, these proteins that can do this. And you just basically mass produce those and use the proteins, not the bugs.

Debora - Yes. You can certainly do that. You can certainly do that. You can use either the bugs, and extract from the bugs or use their proteins, extract their proteins and mass produce it. So there are two ways that you can do it.

Chris - This is then a first step. The microbes are showing you that it's possible. Now it's a question of in some way, optimising this, either directly by fiddling with the microbes, or fiddling with the proteins that they make to produce a more optimal, more efficient system.

Debora - That's correct.

Chris - Do you think that's going to be feasible?

Debora - I think it will. I think it's feasible considering how our technology is evolving. I think it's going to be totally feasible. Yes.


Add a comment