Electroactivity of the magnetotactic bacteria Magnetospirillum magneticum AMB-1 and Magnetospirillum gryphiswaldense MSR-1

Abstract Magnetotactic bacteria reside in sediments and stratified water columns. They are named after their ability to synthesize internal magnetic particles that allow them to align and swim along the Earth’s magnetic field lines. Here, we show that two magnetotactic species, Magnetospirillum magneticum strain AMB-1 and Magnetospirillum gryphiswaldense strain MSR-1, are electroactive. Both M. magneticum and M. gryphiswaldense were able to generate current in microbial fuel cells with maximum power densities of 27 and 11 µW/m 2 , respectively. In the presence of the electron shuttle resazurin both species were able to reduce the crystalline iron oxide hematite (Fe 2 O 3 ). In addition, M. magneticum could reduce poorly crystalline iron oxide (FeOOH). Our study adds M. magneticum and M. gryphiswaldense to the growing list of known electroactive bacteria, and implies that electroactivity might be common for bacteria within the Magnetospirillum genus.