title: Nanobacteria-like calcite single crystals at the surface of the Tataouine meteorite.
abstract: 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.
authors.affiliation: Laboratoire de Minéralogie-Cristallographie, Unité 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. benzerar@lmcp.jussieu.fr
authors.forename: Karim
authors.initials: K
authors.lastname: Benzerara
authors.forename: Nicolas
authors.initials: N
authors.lastname: Menguy
authors.forename: Francois
authors.initials: F
authors.lastname: Guyot
authors.forename: Christian
authors.initials: C
authors.lastname: Dominici
authors.forename: Philippe
authors.initials: P
authors.lastname: Gillet
mesh_terms: D001419:Bacteria / Q000648:ultrastructure*; D002119:Calcium Carbonate / Q000737:chemistry*; D005844:Geology / Q000379:methods; D019110:Meteoroids; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D008903:Minerals
chemical_list: D008903:Minerals; D002119:Calcium Carbonate