Microbes Use Tiny Magnets as Batteries

Summary

Understanding subsurface electron flow 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 Earth’s near surface and possibly halt toxins from spreading. The scientific challenge is 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. In a recent study, scientists at the University of Tuebingen, University of Manchester, and Pacific Northwest National Laboratory discovered that during the day, one species of bacteria withdraws electrons from the iron-based mineral magnetite. At night, another species adds electrons back to the mineral, where the electrons reside until the daytime 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 the Department of Energy’s Environmental Molecular Sciences Laboratory. 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.

Principal Investigator(s)

James Bryne
University of Tuebingen

Carolyn Pearce
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 Office of Biological and Environmental Research within the U.S. Department of Energy Office of Science.

References

Byrne, J. M., N. Klueglein, C. Pearce, K. M. Rosso, E. Appel, and A. Kappler. “Redox cycling of Fe(II) and Fe(III) in magnetite by Fe-metabolizing bacteria.” Science 347(6229),1473–76 (2015). [DOI:10.1126/science.aaa4834].