Bacteria in the Tatahouine meteorite: nanometric-scale life in rocks

We present a study of the textural signature of terrestrial weathering and related biological activity in the Tatahouine meteorite. Scanning and trans mission electron microscopy images obtained on the weathered samples of the Tatahouine meteorite and surrounding soil show two types of bacteria-like forms lying on mineral surfaces: (1) rod-shaped forms (RSF) about 70-80 nm wide and ranging from 100 nm to 600 nm in length; (2) ovoid forms (OVF) wit h diameters between 70 and 300 nm, They look like single cells surrounded b y a cell wall. Only Na, K, C, O and N with traces of P and S are observed i n the bulk of these objects. The chemical analyses and electron diffraction patterns confirm that the RSF and OVF cannot be magnetite or other iron ox ides, iron hydroxides, silicates or carbonates. The rites of the RSF and OV F are below those commonly observed for bacteria but are very similar to so me bacteria-like forms described in the Martian meteorite ALH84001. All the previous observations strongly suggest that they are bacteria or their rem nants. This conclusion is further supported by microbiological experiments in which pleomorphic bacteria with morphology similar to the OVF and RSF ob jects are obtained from biological culture of the soil surrounding the mete orite pieces. The present results show that bacteriomorphs of diameter less ' than 100 nm may in fact represent real bacteria or their remnants. (C) 20 00 Elsevier Science B.V. All rights reserved.