Microbes can extract valuable elements from rocks in space

Recent experiments aboard the International Space Station have shown that some microbes can harvest valuable rare earth elements from rocks, even when exposed to microgravity conditions. The unexpected discovery shows how microbes could increase our ability to live and work in space.

On Earth, some microscopic organisms have proven their worth as effective miners by extracting rare earth elements (REEs) from rocks. New experimental evidence published today in Nature Communications shows that, when it comes to leaching REE from rocks, at least one strain of bacteria is largely unaffected by microgravity and low gravity conditions. This is potentially good news for future space explorers, as biomination of microbes could provide a means to acquire REEs in space, on the Moon or Mars.

REEs are vital for the production of commercial electronic components (such as those found in your smartphone) and for the production of alloys. The problem with REEs, aside from their complicated names (e.g. lanthanum, cerium, neodymium, yttrium, praseodymium, just to name a few), is not as uncommon as they are notoriously difficult to mine and extract, making them a serious pain in the ass. In addition to the rising costs of mining and refining, the collection of these elements is both ecologically and environmentally hostile, and the insatiable quest to obtain them often results in civil strife, which is why they are often referred to as “conflict minerals”. Frustratingly, these elements, with their unique magnetic and catalytic properties, are devoid of vital substitutes.

This is why microbes are recruited to help, with a technique known as biomining.

“Microbes can be specific in the type of elements they bind and allow us to eliminate large amounts of environmentally harmful chemicals, such as cyanides, traditionally used to leach elements from rocks,” Charles Cockell, lead author of the new study and an astrobiologist from the University of Edinburgh explained in an email. “Nowadays, we can even design them to be better miners.”

These microbes work their magic by producing sugars, which bind to REEs. This causes the elements to concentrate together, making extraction easier.

To determine if biomination is possible off Earth, an experiment was organized at the International Space Station, a unique laboratory in which microbes can be exposed to conditions of microgravity and low gravity. That altered gravity could affect microbes’ ability to perform their tasks was a real possibility, as such conditions “are known to affect microbial growth and metabolic processes,” according to the study.

“Low gravity is known to reduce the sedimentation of microbes and thereby reduce the mixing and flow of nutrients to and waste from microbes,” Cockell said. “So we might expect that this could indirectly affect the growth of microbes and how they interact with rocks, and therefore their ability to biominize those rocks.”

Three different bacteria were used in the experiment: Sphingomonas desiccabilis, Bacillus subtilis, is Cupriavidus metallidurans. These tests were commissioned by the European Space Agency as part of its BioRock experiment, conducted on the ISS in 2019. The aim of the project was to see if microbes could filter an assortment of REEs from basalt – a good analogue for materials found on the Moon. and on Mars.

The authors measured the extraction efficiency of microbes when exposed to three different conditions: microgravity, Mars gravity, and Earth gravity. To do this, the ISS astronauts placed the microbes in a miniaturized biomining reactor known as KUBIK.

“This is an incubator that controls the temperature, but it also contains a ring that goes around it – a centrifuge,” explained Cockell. “We put our biomining reactors on the ring and spin them at the right speed to simulate the gravity of Mars and Earth – Earth’s gravity is a ‘control’ experiment for making comparisons.”

Of the three bacterial species, only one, S. desiccabilis, showed the ability to leach REE from basaltic rock under all conditions. This bacterium did not appear to be disturbed by any of the three gravitational environments, showing an extraction efficiency of 70% for the cerium and neodymium REEs. The other two bacteria showed very poor performance or no capacity when exposed to any of the experimental conditions.

As to why S. desiccabilis did so well while his fellow microbials didn’t, Cockell said his team thinks it’s because this bacterium produces “a lot of long-chain sugars that have many binding sites on them that bind rare earth elements.” The other microbes didn’t, he said, adding, “We wondered if other microbes could be stimulated to biominate by the stressful conditions of nutrient deficiency in microgravity – which is why we sent them – but microgravity doesn’t change the their ability or allow them to biominate. “

The new research shows that specific microbes (there may be more or, if not, scientists could produce genetically engineered versions) will likely function as REE extractors in space. It goes without saying that these microbes would die if exposed to the elements, so this imagined refining process will require some smart technologies. Cockell imagines bioreactors filled with gas and fluid near lunar habitats, on Mars and even on asteroids. The promising rocks would be placed in the reactor along with the necessary microbes, the chamber sealed and pressurized, and voila, you have started the biomination process.

Cockell said it’s important to point out that his team isn’t proposing to mine in space and deliver materials to Earth.

“At the moment, it’s not economically viable,” he said. “However, biomination and other forms of extraction can be used to provide the elements necessary for a long-term human presence in space. Our experiment explored and demonstrated the potentially important role of microbes in facilitating human expansion into space. “

The authors will now turn their attention to an exciting experiment, called BioAsteroid, which will be launched on the ISS in December. The experiment will use meteorite material as a substitute for asteroid rock, as well as fungi with a propensity for rock mining. BioAsteroid will also involve exposure to microgravity conditions, to evaluate the feasibility of using fungi for asteroid biomining.