FIG. 7.

Microbial forms under the Atacama surface bound to halite crystals. Scanning electron microscope images and energy dispersive X-ray (EDX) spectra showed halite crystals with incipiently mineralized microbial cells. (A) Halite crystal with elongated morphology and rough surface showing nanoparticles and mineralized microbial cell-like structures (arrows) on its surface. EDX spectrum of the crystal (inset) indicates that it is composed of Na and Cl (halite). (B) Close-up of two microbial cells from (A) attached to the halite crystal surface (arrows). (C) Halite crystal showing empty voids which correspond to mineralized moulds of degraded microbial cells, most probably bacteria (arrows), some of them with clear vibriod form. Note that EDX spectrum displays Na, Cl, C, O, and N. The four latter elements come, most probably, from organic compounds of microbial cells. The pie chart shows the percentage of the main elements. (D) Close-up of two microbial cells attached to the halite crystal surface (arrow) and the EDX spectrum of one of them. The EDX spectra correspond to the green squares. Color images available online at www.liebertonline.com/ast