It has long been known that the bacteria Mycobacterium smegmatis have one interesting feature – they are able to convert hydrogen contained in the air into electrical energy. Thanks to this, the microbe can survive in the harshest conditions where there are no other sources of energy. In particular, this bacterium lives in Antarctic soil, volcanic craters, deep oceans, etc. This ability of M. smegmatis has been known to scientists for a long time, but now they have discovered the enzyme that is responsible for converting hydrogen into electricity, and understand how it works. This enzyme can be used to produce electricity from the air in the truest sense of the word.
How bacteria extract energy from the air
Mycobacterium smegmatis is related to the bacteria that cause leprosy and tuberculosis in humans, but unlike its counterparts, it is not pathogenic. The enzyme that helps M. smegmatis extract energy from the air is called Huc. It is still a mystery how exactly it works. To find out, scientists isolated the enzyme from microbes using chromatography. This laboratory method allows the separation of mixtures into individual components. They then studied the atomic structure of the enzyme using cryoelectron microscopy.
It must be said that cryoelectron microscopy appeared relatively recently. In 2017, its inventors received the Nobel Prize in Chemistry. Using this method, the authors of the work sent electrons to a frozen sample of Huc, which made it possible to determine its atomic structure, as well as to identify the electrical paths that the enzyme uses to flow electrons.
As it turned out, the enzyme contains a structure called the “active center”. This structure contains charged iron and nickel ions. When hydrogen molecules enter the active center, they are trapped between two metal ions, where they lose their electrons. These electrons “pulled out” from hydrogen are directed by a stream from the center to the shell of the enzyme, that is, an electric current arises. This is reported in a study published recently in the journal Nature. As the scientists explain, the electrons that are absorbed by the ions of the active center, including the nickel ion, are transferred to the surface of the enzyme by a molecular wire, which is a cluster of iron and sulfur ions.
Is it possible to extract electricity from the air?
If you connect an electrode to the Huc surface, you can get an electrical circuit, and thus generate electricity. But how realistic is this in practice? Studies have shown that the enzyme can be stored for a long time. Moreover, it is resistant to various environmental influences. In particular, it withstands heating up to 80 degrees Celsius and freezing.
To generate electricity, the enzyme needs hydrogen in negligible amounts. That is, in the air we breathe, there is enough hydrogen to generate electricity. Given all of these properties, plus the fact that bacteria are easy and quick to grow and live everywhere, Huc could be an ideal source of energy.
Of course, it is unlikely that it will be possible to generate electricity on such a scale that it would be possible to power an entire city or at least a house. However, bacteria can be used to create biological batteries for gadgets that do not need chargers. The Huc-based battery will “charge” with air, and therefore will not discharge.
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However, scientists have discovered an interesting property of the enzyme – the more hydrogen it gets, the more electricity it generates. This means that pure hydrogen can be used as a fuel cell. In this case, electricity can be enough not only to power smart watches, smartphones or laptops, but also electric vehicles.
Finally, we recall that recently scientists have come to the conclusion that the bowels of the Earth contain a large amount of natural hydrogen that can be renewed. Cheap hydrogen and electricity “out of thin air”, albeit on a limited scale, can really lead to a revolution in the energy sector. In addition, scientists have managed to achieve some positive results in the field of thermonuclear energy, on which some scientists also have high hopes.