Recently, researchers from Institute of Microbiology, Guangdong Academy of Sciences, Aarhus University and several other universities found a novel microbial electrical network. The work was published in Nature Communications with a title of “Long-distance electron transfer in a filamentous Gram-positive bacterium”. The first author is Prof. Yonggang Yang from Institute of Microbiology, Guangdong Academy of Sciences, the corresponding authors are Prof. Meiying Xu from Institute of Microbiology, Guangdong Academy of Sciences and Prof. Mingdong Dong from Aarhus University.
Increasing evidences demonstrating that the microbial world on the earth is connected and communicated with electricity. Electrical wire networks in the scale of micrometer or centimeter have been founded in many microorganisms and environments, and were believed to play important roles in biogeochemical process, pollutant degradation and bioenergy recovery.
Since the first report of bacterial conductive nanowire in 2005, over ten Gram-negative bacteria and one archaea have been reported to generate conductive wires and forming electrical networks. However, Gram-positive bacteria, as an essential and ubiquitous member in the microbial world, are still missing in these electrical networks. It seems like they are excluded because of their thick and nonconductive cell walls.
Recently, an international group including researchers from China, Denmark and Belgium showed evidences that Gram-positive bacteria could also be key knots in the electrical networks. Lysinibacillus varians, a Gram-positive bacterium isolated from river sediment, can form centimeter-scale and conductive cellular networks when transferring electrons graphite electrodes in microbial electrochemical systems. One single L. varians cell in the networks can grow into over one millimeter. In the network, L. varians can generate micrometer-long conductive nanowires connecting to each other and form a secondary but conductive network while the filamentous cells forming nonconductive frames.
Previous reports have shown two types of microbial electrical networks, one comprises short cells with extracellular conductive nanowires (e.g. Geobacter biofilms) and the other comprises filamentous cells with conductive envelops (e.g. cable bacteria networks). L. varians network comprises filamentous cells and extracellular conductive nanowires, combining the properties of two known microbial electrical networks. The finding of L. varians electrical network provides an important piece to a complete understanding of the microbial electrical networks in natural environments.
Further researches such as the nanowire composition and structure, electrical interactions with other bacteria, cell shape regulation and potential applications as biomaterials of L. varians are ongoing in the international research group.