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Microbial Polysaccharides Template Assembly of Nanocrystal Fibers
Clara S. Chan,1*Gelsomina De Stasio,2,4*Susan A. Welch,3Marco Girasole,5Bradley H. Frazer,2,4Maria V. Nesterova,3Sirine Fakra,6Jillian F. Banfield1,3
Biological systems can produce extraordinary inorganic structuresand morphologies. The mechanisms of synthesis are poorly understoodbut are of great interest for engineering novel materials. Weuse spectromicroscopy to show that microbially generated submicrometer-diameteriron oxyhydroxide (FeOOH) filaments contain polysaccharides,providing an explanation for the formation of akaganeite pseudo–singlecrystals with aspect ratios of 1000:1. We infer that the cellsextrude the polysaccharide strands to localize FeOOH precipitationin proximity to the cell membrane to harness the proton gradientfor energy generation. Characterization of organic compoundswith high spatial resolution, correlated with mineralogicalinformation, should improve our understanding of biomineralizationmechanisms.
1 Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, USA. 2 Department of Physics, University of Wisconsin, Madison, WI 53706, USA. 3 Department of Geology and Geophysics, University of Wisconsin, Madison, WI 53706, USA. 4 Synchrotron Radiation Center, Stoughton, WI 53589, USA. 5 Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Rome 00044, Italy. 6 Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
* These authors contributed equally to this work.
Present address: Department of Earth and Marine Sciences, ResearchSchool of Earth Sciences, and Cooperative Research Centre forLandscape Environments and Mineral Exploration, Australian NationalUniversity, Canberra, ACT 0200, Australia.
Present address: Department of Chemistry and Biochemistry, MontanaState University, Bozeman, MT 59717, USA.
To whom correspondence should be addressed. E-mail: jill{at}eps.berkeley.edu (J.F.B.), pupa{at}src.wisc.edu (G.D.S.)
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1000:1. We infer that the cells extrude the polysaccharide strands to localize FeOOH precipitation in proximity to the cell membrane to harness the proton gradient for energy generation. Characterization of organic compounds with high spatial resolution, correlated with mineralogical information, should improve our understanding of biomineralization mechanisms. 
Present address: Department of Earth and Marine Sciences, Research School of Earth Sciences, and Cooperative Research Centre for Landscape Environments and Mineral Exploration, Australian National University, Canberra, ACT 0200, Australia. 
Present address: Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA. 
To whom correspondence should be addressed. E-mail: 
