The first evidence is in, in the case of mysterious microbes

The image shows how a micro-organism (grey cell) is using electrons for energy.

Conductive iron sulfide (FeS) nanoparticles were biosynthesized by sulfate-reducing bacteria (SRB) extracellularly, intracellularly, and on the cell surface. These FeS nanoparticles enabled SRB cells of direct electron (e−) uptake from an extracellular electrode coupled with energy acquisition, providing critical insights into the physiological and biogeochemical role of naturally abundant FeS nanoparticles.

Bacteria are found in every habitat on Earth – soil, rock, oceans and even arctic snow. Like all living things, bacteria need energy to live and grow. Bacteria can get energy in a variety of ways, including well known processes like photosynthesis and consumption of organic compounds. But there are other, more mysterious ways too.

Many bacteria create nanoparticles that help them survive unfavourable conditions. In oxygen-free environments a group of bacteria called sulfate-reducing bacteria (SRB) commonly create iron sulfide (FeS) nanoparticles on their cell surface. However, little is known about the biological function of these nanoparticles.

In a paper just published in the prestigious journal Angewandte Chemie International Edition, FSP postdoc Xiao Deng and colleagues showed that sulfate-reducing bacteria can use these FeS nanoparticles on their cell surface to acquire energy – i.e. electrons – directly from electrodes, and that this is sufficient for cell growth.

This is the first report on the electron uptake process in SRB using self-synthesized nanoparticles. The finding suggests that electron uptake capability may be common in bacteria and has implications for how we understand diverse environmentally and economically important biogeochemical cycles, including of carbon, sulphur, and iron cycling as well as microbial iron corrosion.