Some soil bacteria, for example, can gobble up hydrogen from the air and use it for fuel if starved of any other food.

It's exactly this microbiological trickery that set researchers from Monash University in Australia on a long path to locating and isolating an enzyme from Mycobacterium smegmatis that processes the consumed hydrogen and outputs it as electricity. Now, this has the potential to be harnessed for use to power things such as small devices and implants.

"We've known for some time that bacteria can use the trace hydrogen in the air as a source of energy to help them grow and survive, including in Antarctic soils, volcanic craters, and the deep ocean," said Chris Greening, microbiology professor at Monash and co-lead of this study. "But we didn't know how they did this, until now."

While hydrogen only makes up 0.00005% of the atmosphere, this isolated hydrogen catalyzing enzyme, which the team called Huc, is able to consume it easily. And while bacteria removes 70 million tonnes [77 million tons] of hydrogen yearly from the air, the molecular structure of Huc sees the enzyme split the hydrogen molecules to form an electron transport chain, essentially producing an electrical circuit in the cell.

"Huc is extraordinarily efficient," says lead author Rhys Grinter from the university's Biomedicine Discovery Institute. "Unlike all other known enzymes and chemical catalysts, it even consumes hydrogen below atmospheric levels – as little as 0.00005% of the air we breathe."

It took the team five years and several dead ends to isolate Huc, but once they did they were amazed at many aspects of this little powerhouse.