SREL Reprint #2796

 

 

 

Formation of tabular single-domain magnetite induced by Geobacter metallireducens GS-15

Hojatollah Vali1,2, Benjamin Weiss3,5, Yi-Liang Li6, S. Kelly Sears1, Soon Sam Kim4, Joseph L. Kirschvink3,
and Chuanlun L. Zhang6

1Department of Anatomy and Cell Biology and Facility for Electron Microscopy Research, McGill University, Montréal, QC, Canada H3A 2B2
2Department of Earth and Planetary Sciences, McGill University, Montréal, QC, Canada H3A 2A7
3Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125
4Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91125
5Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139
6Savannah River Ecology Laboratory, University of Georgia, Aiken, SC 29803

Abstract: Distinct morphological characteristics of magnetite formed intracellularly by magnetic bacteria (magnetosome) are invoked as compelling evidence for biological activity on Earth and possibly on Mars. Crystals of magnetite produced extracellularly by a variety of bacteria including Geobacter metallireducens GS-15, thermophilic bacteria, and psychrotolerant bacteria are, however, traditionally not thought to have nearly as distinct morphologies. The size and shape of extracellular magnetite depend on the culture conditions and type of bacteria. Under typical CO2-rich culture conditions, GS-15 is known to produce superparamagnetic magnetite (crystal diameters of approximately <30 nm). ln the current study, we were able to produce a unique form of tabular, single-domain magnetite under nontraditional (low-CO2) culture conditions. This magnetite has a distinct crystal habit and magnetic properties. This magnetite could be used as a biosignature to recognize ancient biological activities in terrestrial and extraterrestrial environments and also may be a major carrier of the magnetization in natural sediments.

SREL Reprint #2796

Vali, H., B. Weiss, Y. Li, S. K. Sears, S. S. Kim, J. L. Kirschvink, and C. L. Zhang. 2004. Formation of tabular single-domain magnetite induced by Geobacter metallireducens GS-15. Proceedings of the National Academy of Sciences 101:16121-16126.

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