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Archaea
Volume 2016, Article ID 4706532, 11 pages
http://dx.doi.org/10.1155/2016/4706532
Research Article

Discovery and Characterization of Iron Sulfide and Polyphosphate Bodies Coexisting in Archaeoglobus fulgidus Cells

1Department of Microbiology, Immunology, and Molecular Genetics, UCLA, Los Angeles, CA 90095, USA
2Electron Imaging Center for Nanomachines, California NanoSystems Institute, UCLA, Los Angeles, CA 90095, USA
3The UCLA Biomedical Engineering Interdepartmental Program, UCLA, Los Angeles, CA 09905, USA
4Institute of Industrial Biotechnology, GC University, Lahore 54000, Pakistan
5The UCLA-DOE Institute of Genomics and Proteomics, UCLA, Los Angeles, CA 90095, USA

Received 11 December 2015; Accepted 20 March 2016

Academic Editor: Harald Engelhardt

Copyright © 2016 Daniel B. Toso et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Inorganic storage granules have long been recognized in bacterial and eukaryotic cells but were only recently identified in archaeal cells. Here, we report the cellular organization and chemical compositions of storage granules in the Euryarchaeon, Archaeoglobus fulgidus strain VC16, a hyperthermophilic, anaerobic, and sulfate-reducing microorganism. Dense granules were apparent in A. fulgidus cells imaged by cryo electron microscopy (cryoEM) but not so by negative stain electron microscopy. Cryo electron tomography (cryoET) revealed that each cell contains one to several dense granules located near the cell membrane. Energy dispersive X-ray (EDX) spectroscopy and scanning transmission electron microscopy (STEM) show that, surprisingly, each cell contains not just one but often two types of granules with different elemental compositions. One type, named iron sulfide body (ISB), is composed mainly of the elements iron and sulfur plus copper; and the other one, called polyphosphate body (PPB), is composed of phosphorus and oxygen plus magnesium, calcium, and aluminum. PPBs are likely used for energy storage and/or metal sequestration/detoxification. ISBs could result from the reduction of sulfate to sulfide via anaerobic energy harvesting pathways and may be associated with energy and/or metal storage or detoxification. The exceptional ability of these archaeal cells to sequester different elements may have novel bioengineering applications.