Newly Identified Bacteria Exhibits Electrical Conductivity

A novel species of bacteria, capable of conducting electricity, has been discovered on a brackish beach in Oregon. This newly identified organism has been designated Candidatus Electrothrix yaqonensis, honoring the Yaquina tribe of Native Americans who historically inhabited the surrounding region of Yaquina Bay.

This bacterium is categorized as a type of cable bacteria, characterized by its rod-shaped structure and the ability to form long chains through connected outer membranes. These filaments can extend several centimeters in length. Cable bacteria are unique in the microbial world as they possess electrical conductivity, a trait attributed to their distinctive metabolic processes. They generate electrons through the oxidation of sulfides found in deeper sediment layers and subsequently transfer these electrons to the surface, where they interact with oxygen and nitric acid.

Prior to this discovery, 25 species of cable bacteria had been identified, classified into two primary genera: Candidatus Electrothrix, which thrive in saltwater, and Candidatus Electronema, which inhabit freshwater and brackish environments. The newly discovered species exhibits genetic and metabolic characteristics from both these genera, suggesting it serves as a link to an earlier evolutionary branch within the Candidatus Electrothrix lineage.

One of the most notable features of Candidatus Electrothrix yaqonensis is its structural composition. Unlike other cable bacteria that have outer shells adorned with ridges resembling mountain ranges, this new species possesses significantly thicker ridges, averaging 228 nanometers in thickness--up to three times greater than previously noted species. These ridges are organized in a spiral formation, and the filament itself is encased in a robust, transparent sheath, which is believed to protect it from external environmental factors, although it does not participate in electrical conduction.

Researchers found that within the ridges of this bacterium lies a fiber that contains a nickel-centered metal complex, functioning as a 'biological wire' to facilitate the efficient movement of electrons along the filament. When isolated filaments were placed on a gold electrode and subjected to a voltage, the results indicated high electrical conductivity, as evidenced by a linear, symmetrical current-voltage curve. The electrical resistance measured for this new species was approximately 370 kilo-ohms, matching or surpassing the conductivity of previously known cable bacteria.

Genomic analysis revealed that Candidatus Electrothrix yaqonensis exhibits a unique genetic mosaicism, integrating characteristics from both the Candidatus Electrothrix and Candidatus Electronema genera. This is evident in its cytochrome protein, which typically contains a single heme in the Candidatus Electrothrix genus but has two hemes in this new species. This adaptation showcases the bacterium's evolution in response to its brackish habitat, where salinity levels fluctuate.

Future research aims to elucidate the mechanisms behind the formation of the protective sheath and the self-assembly process of its conductive fibers. The unique combination of high electrical conductivity and adaptability to brackish environments positions Candidatus Electrothrix yaqonensis as a promising candidate for applications in bioelectronics. It has potential implications for the development of biodegradable electronic devices and biosensors, as well as for environmental remediation efforts targeting heavy metals and organic pollutants in sedimentary ecosystems.