Microbes use tiny magnets as batteries
James M. Bryne
Center for Applied Geosciences, University of Tuebingen, Sigwartstrasse 10, 72076 Tuebingen, Germany
Understanding electron flow underground is vital in understanding elemental cycling and remediating subsurface pollutants, including those from recent energy technologies and historic waste sites. Research into the flow of electrons can show how certain minerals and bacteria work together, via reduction-oxidation reactions, to shape the geochemical landscape at the Earth’s near surface and also possibly halt toxins from spreading. The scientific challenge has been knowing how to unravel complex communities of organisms and mineral assemblages in nature into key cooperative subsystems that can be studied in the laboratory to determine how they work. At the University of Tuebingen, University of Manchester, and Pacific Northwest National Laboratory, scientists discovered that during the day, one species of bacteria withdraws electrons from the iron-based mineral magnetite, and at night, another species adds electrons back to the mineral, where the electrons reside until the day time bacteria are active. The phototrophic Fe(II)-oxidizing Rhodopseudomonas palustris TIE-1 and the anaerobic Fe(III)-reducing Geobacter sulfurreducens work together to use magnetite's iron ions as both electron sources and sinks under different day and night conditions. The researchers used a host of instruments to make this discovery, including transmission electron microscopy resources at DOE's EMSL. The research shows that the common iron oxide mineral magnetite can serve as a naturally occurring battery for two very different types of bacteria that depend on iron to survive, revealing that a single mineral can serve as a platform for microbial diversity in nature.
James M. Byrne, Nicole Klueglein, Carolyn Pearce, Kevin M. Rosso, Erwin Appel, Andreas Kappler. 2015. " Redox cycling of Fe(II) and Fe(III) in magnetite by Fe-metabolizing bacteria." Science 347(6229):1473-1476. DOI: 10.1126/science.aaa4834
Performers: University of Tuebingen, University of Manchester, and Pacific Northwest National Laboratory
Funding: This work was funded by the Deutsche Forschungsgemeinschaft. Part of this work was funded by the Pacific Northwest National Laboratory Science Focus Area, the Subsurface Biogeochemical Research program of the U.S. Department of Energy Office of Biological and Environmental Research.
User Facility: EMSL: Environmental spectroscopy laboratory; transmission electron microscopy
Caption: In the subsurface environment, below the water level, iron-oxidizing bacteria strip electrons from the naturally occurring battery (left); the reducing bacteria, which are active at night, add electrons, effectively re-charging the battery (right).
Credit: The image was created at the University of Tuebingen, which owns the rights. It was not used in the journal. The university's public relations department has approved use for it to be provided to the U.S. Department of Energy.