Although we usually relate bacteria with diseases, the truth is that this group has a kind of ‘superpowers’ that range from ‘self-vaccination’ to eating plastic, passing through survival in environments as hostile as space. They are also experts at obtaining energy from almost nothing: scientists have long known that many are capable of generating electricity from thin air in environments as hostile as volcanoes or the poles. However, the system they used for this was unknown. Now, Australian researchers have discovered the enzyme responsible for this ‘magical’ transformation and say their discovery is a first step towards creating natural batteries that produce clean energy.

The team, led by Rhys Grinter, Ashleigh Kropp and Chris Greening, researchers at the Biomedical Discovery Institute at Monash University in Melbourne, Australia, have already shown that many bacteria use atmospheric hydrogen as an energy source in nutrient-poor environments; that is, just by ‘breathing’, even in places hostile to life, they generate electricity that helps them to survive.

“We’ve known for some time that trace amounts of hydrogen in the air can be used by bacteria as an energy source to help them grow, including in Antarctic soils, volcanic craters and in the deep ocean,” explains Greening. “But we didn’t know how they did it. Until now.” The results of his new research have just been published in the journal ‘Nature’.

huck’s secret

The team focused on an enzyme from the bacteria Mycobacterium smegmatis. To call huck, converts hydrogen gas into electrical current. “Huc is extraordinarily efficient,” says Grinter. Unlike all other known enzymes and chemical catalysts, it consumes hydrogen below atmospheric levels, just 0.00005% of the air we breathe.”

The researchers used several methods to reveal the molecular model of atmospheric hydrogen oxidation. They used advanced microscopy (cryo-EM) to determine their atomic structure and electrical pathways, surpassing previously established limits to produce the most resolved enzyme structure reported by this method to date. They also used a technique called electrochemistry to demonstrate that the purified enzyme creates electricity in minute concentrations of hydrogen.

In the laboratory, they also demonstrated that it is possible to store purified Huc for long periods. “It’s incredibly stable. You can freeze the enzyme or heat it to 80 degrees Celsius and it retains its power to generate energy,” explains Kropp. This reflects that this enzyme helps bacteria survive in the most extreme environments.”

huck is a’natural battery‘ which produces a sustained electrical current from air or if hydrogen is added to it. The authors note that although this research is at an early stage, the discovery of this enzyme has “considerable potential for developing small air-powered devices, for example, as an alternative to solar-powered devices.”

Possibility of cultivation

The next question is obvious: where can we get more of this Huc that produces electricity out of thin air? The authors say that not only Mycobacterium smegmatis this enzyme is extracted: other common bacteria have similar enzymes and can be grown in large numbers, “which means we have access to a sustainable source of the enzyme,” they note.

“Once we produce Huc in sufficient quantities, the sky is literally the limit for using it to produce clean energy,” notes Grinter.