Recently, scientists discovered an entirely new microbe that is capable of transferring electrical current. This electrified family member of the Desulfobaceae, while waiting for its scientific name, is aptly named “cable bacteria”. Danish researchers observed the phenomenon in lab experiments with marine sediments from the Baltic Sea. A study group from the VIB (Flemish Institute for Biotechnology) and NIOZ (Royal Netherlands Institute for Sea Research) confirmed that this process occurs naturally in the bottom of the sea and are now looking for opportunities to exploit this exciting new discovery.
It’s not like quorum sensing
It is well known that bacteria can communicate by sensing molecules produced by their neighbors. However, these chemical signals travel by diffusion and are only effective when released in the immediate neighborhood of the bacteria, for example, in biofilms. In contrast, cable bacteria transfer electrons to one another over a line of 20,000 cells and manage to span a distance of up to a couple of centimeters.
From sulfide to oxygen
The bacteria living in the deeper sediments, where no oxygen is present, convert sulfide (S2-) to sulfur (S). They pull away electrons from the sulfide and pass them via a line of bacteria to the oxygen-rich surface. The bacteria on top give off the electrons to oxygen (O2), converting it to H2O. By doing so, they generate electrical current. Thanks to this mechanism, sulfate metabolism (conversion of SO24- to H2S) during degradation of organic matter can be continued, as it removes sulfide from the sediments.
The current has a switch
Interestingly, this mechanism switches off when less oxygen is available at the surface. Studies have shown that bacteria are capable of rapidly modifying their electron harvesting capacity based on the availability of oxygen.
Bacterial electricity and bio-electrical applications
This discovery forms a platform for a whole range of bio-electrochemical applications. Think of microbial fuel cells, electricity driven environmental remediation or bio-electrical materials such as solar panels and smartphones containing tiny conducting wires of bacterial origin. The possibilities are huge!
Reference
