This study explores the photosynthetic microbial colonization of rhyolitic ignimbrites in Lomas de Tilocalar, a hyper-arid region of the Atacama Desert, Chile. Colonization appeared in the form of a green layer a few millimeters beneath the ignimbrite surface. Some ignimbrite rocks revealed two distinct micromorphological areas of identical mineralogical and chemical composition but different textural properties. According to texture, colonization patterns varied in terms of the extension and depth of colonization. The diversity of photosynthetic microorganisms was assessed by denaturing gradient gel electrophoresis (DGGE) of the 23S rRNA gene and by generating clone libraries of the 16S rRNA gene. We observed a low diversity of photosynthetic microorganisms colonizing the ignimbrite microhabitat. Most rRNA gene sequences recovered greatly resembled those of Chroococcidiopsis hypolith clones from arid deserts. These results point to highly restrictive conditions of the hyper-arid Atacama Desert conditioning the diversity of cyanobacteria, and suggest that microbial colonization and composition patterns might be determined by the microscale physicochemical properties of the ignimbrite rocks.

This study was supported by grants CGL2010-16004 and CTM2012-38222-C02-02 and CGL2013-42509 from the Spanish Ministry of Economy and Competitiveness and by a predoctoral FPI fellowship program (BES-2007-15145).

Received 23 September 2014

Peer reviewed