"Mining" bacteria turn toxic copper ions into useful metal
Copper is one of the most widely used metals, but extracting and refining it into a useful form can be energy intensive and requires harsh chemical treatments. But now, researchers at the University of Houston have discovered bacteria that naturally convert toxic copper ions into metallic copper.
No matter how inhospitable an environment seems to us, chances are high that some form of life will find a way to thrive there. Copper mines are one such example – copper ores can be toxic – but certain species of bacteria have been found living there. And in the new study, researchers investigated what they’re actually doing in these mines.
Using an electron microscope, the team examined a species of Bacillus that had been isolated from a copper mine in Brazil. They found that the bacteria were able to survive by converting toxic copper sulfate ions into a stable, single-atom form known as zero-valent copper. This is the handy metallic copper that we’re most familiar with.
“The microbes utilize a unique biological pathway with an array of proteins that can extract copper (II) (Cu2+) and convert it into single-atom zero-valent copper (Cu0),” says Debora Rodrigues, co-author of the study. “The aim of the microbes is to create a less toxic environment for themselves by converting the ionic copper into single-atom copper, but at the same time they make something that is beneficial for us too.”
This find is particularly interesting because our own industrial processes for this conversion are quite environmentally unfriendly, requiring toxic solvents and producing dangerous gases like sulfur dioxide. It’s also labor intensive and can be expensive, the team says.
“In terms of chemistry, this is extremely difficult to derive,” says Francisco Robles Hernandez, co-author of the study. “Typically, harsh chemicals are used in order to produce single atoms of any element. This bacterium is creating it naturally, that is very impressive.”
Harnessing bacteria to convert copper into useful forms could end up being safer and more efficient, the team says, and they could allow mines to extract valuable materials from waste streams, such as acid mine drainages. Other species might be performing similar functions too – after all, other bacteria have been found to convert toxic metals into tiny gold nuggets.
However, as usual, there’s the question of just how scalable the process might be for industrial use. The next steps in the study will be to investigate that aspect, and harvest the copper from the bacteria.
The research was published in the journal Science Advances.
Source: University of Houston