Baltic Sea Sediment Microbes Use Conductive Particles to Produce Methane, Study Finds

Researchers from the University of Southern Denmark and Aarhus University have identified how bacteria and methane-producing archaea in Baltic Sea sediments exchange electrons through conductive particles, such as magnetite and black carbon. The study, published in Nature Communications, shows that these particles act as electrical bridges, allowing the microbes to work together without direct contact. The process converts acetate and carbon dioxide into methane, a potent greenhouse gas. The team used genome-resolved metagenomics to recover 24 genomes from a lab culture that had been maintained for a decade. They found a new bacterial genus, Candidatus Geosyntrophus acetoxidans, which oxidizes acetate and releases electrons through specialized proteins and pili. A Methanosarcina archaeon takes up those electrons to reduce carbon dioxide to methane. Both organisms attach to the same conductive grains, but do not need to touch each other. The findings suggest that naturally occurring conductive particles in coastal sediments may support methane production in ways not fully captured in current models. However, the contribution to real-world methane emissions remains unclear. The researchers call for field surveys and direct measurements in particle-rich environments to determine how widespread this process is.