http://www.pnas.org/cgi/content/abstract/0832464100v1
Proc. Natl. Acad. Sci. USA, 10.1073/pnas.0832464100 Geology Nanobacteria-like calcite single crystals at the surface of the Tataouine meteorite Karim Benzerara *, Nicolas Menguy *, Fran�ois Guyot *, Christian Dominici , and Philippe Gillet *Laboratoire de Min�ralogie-Cristallographie, Unit� Mixte de Recherche 7590 Centre National de la Recherche Scientifique and Institut de Physique du Globe de Paris, 4 Place Jussieu, 75252 Paris Cedex, France; Laboratoire CP2M Facult� des Sciences et Techniques de Saint Jer�me, Universit� d'Aix-Marseille, III, F-13397 Marseille Cedex 20, France; and Laboratoire des Sciences de la Terre, Ecole Normale Sup�rieure Lyon, 46 All�e d'Italie, 69007 Lyon Cedex, France Communicated by Russell J. Hemley, Carnegie Institution, Washington, DC, April 24, 2003 (received for review March 8, 2003) Nanobacteria-like objects evidenced at the surface of the orthopyroxenes of the Tataouine meteorite in South Tunisia have been studied by scanning and transmission electron microscopies. A method of micromanipulation has been developed to ensure that exactly the same objects were studied by both methods. We have shown that the nanobacteria-like objects are spatially correlated with filaments of microorganisms that colonized the surface of the meteoritic pyroxene during its 70 years of residence in the aridic Tataouine soil. Depressions of a few micrometers in depth are observed in the pyroxene below the carbonates, indicating preferential dissolution of the pyroxene and calcite precipitation at these locations. The nanobacteria-like small rods that constitute calcium carbonate rosettes are well crystallized calcite single crystals surrounded by a thin amorphous layer of carbonate composition that smoothes the crystal edges and induces rounded shapes. Those morphologies are unusual for calcite single crystals observed in natural samples. A survey of recent literature suggests that the intervention of organic compounds derived from biological activity is likely in their formation. To whom correspondence should be addressed. E-mail: [EMAIL PROTECTED] ______________________________________________ Meteorite-list mailing list [EMAIL PROTECTED] http://www.pairlist.net/mailman/listinfo/meteorite-list
