The potential for microbial life in the highest-elevation (>6000 m.a.s.l.) mineral soils of the Atacama region

[1] Here we present the first culture-independent microbiological and biogeochemical study of the mineral soils from 6000 m above sea level (m.a.s.l.) on some the highest volcanoes in the Atacama region of Argentina and Chile. These soils experience some of the harshest environmental conditions on Earth including daily temperature fluctuations across the freezing point (with an amplitude of up to 70°C) and intense solar radiation. Soil carbon and water levels are among the lowest yet measured for a terrestrial ecosystem and enzyme activity was near or below detection limits for all microbial enzymes measured. The soil microbial communities were among the simplest yet studied in a terrestrial environment and contained novel Bacteria and Fungi and only one Archaeal phylotype. No photosynthetic organisms were detected but several of the dominant bacterial phylotypes are related to organisms involved in carbon monoxide oxidation on other volcanoes (e.g.,Pseudonocardia and Ktedonobacter spp.). Focused studies of a gene responsible for carbon monoxide oxidation, the large subunit of carbon monoxide dehydrogenase (coxL of CODH), revealed several novel lineages and a broad diversity of coxL genes. Overall our results suggest that a unique microbial community, sustained by diffuse atmospheric and volcanic gases, is barely functioning on these volcanoes, which represent the highest terrestrial ecosystems yet studied.