Exploring Rock-inhabiting Microbes in Atacama Desert's Rocks

High-altitude preandean zone of the Atacama Desert is bare land formed mainly by volcanic rocks. Gypcrete (gypsum) outcrops of hydrothermal origin occur among volcanic deposits. Microbial life in this material was studied here in order to monitor biomolecular composition of endolithic phototrophic microbes harboring the interior parts of gypcretes. Particularly, distribution of photoprotective and photosynthetic pigments related to the microbial colonization was examined using Raman spectroscopy and imaging as a principal method. It allowed a deeper insight into the adaptation strategies of algae and cyanobacteria in such polyextreme environment. Algal cells attributed to the Trebouxiae family varying in color from green to orange were examined and the spectral differences are described. Along with pigments, carotenoids, chlorophyll, also lipids were detected at cellular level. Raman imaging approach allowed to detect carotenoid signal not only within the layer colonized by algae, but also deeper in the gypsum matrix. It is interpreted to be a result of the pigment migration after cell disruption.

Halite pinnacles on the other hand are the geological phenomenons formed within the basins of salt pans (salars) of the Atacama Desert. It is a kind of substrate that may harbor endoevaporitic microbial colonies. Crosscut of a halite pinnacles were examined. Raman spectroscopic imaging was employed as a principal method, combined with advanced fluorescence microscopy. Large field images were examined to monitor the spatial changes in biomolecular response, especially in pigment composition.