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Nieves penitentes are pinnacle-shaped ice structures found at high elevations in the dry Andes. Here we report, using molecular and microscopic approaches, the first description of snow algae communities inhabiting penitente ice at 5,277 m a.s.l., demonstrating a new habitat for snow algae in one of the most extreme environments on Earth. Red ice patches on penitentes contained a microbial community dominated by algae in the genera Chlamydomonas and Chloromonas, both of which were closely related to known snow algae from alpine and polar environments. In contrast, we obtained few snow algae sequences from clear ice, but we did find cyanobacteria sequences and evidence of aeolian-deposited organic matter. Tephra ("soil") within and just downhill from the penitente field hosted more complex bacterial and eukaryotic communities that were significantly different from ice communities in terms of both alpha and beta diversity. In this environment penitentes provide both water and shelter from harsh winds, high UV radiation, and thermal fluctuations, creating an oasis in an otherwise extreme landscape. Intriguingly, recent planetary investigations have suggested the existence of penitente-like structures on other planetary bodies of our solar system. Therefore, penitentes and the harsh environment that surrounds them provide a new terrestrial analog for astrobiological studies of life beyond Earth. [ABSTRACT FROM AUTHOR]

Here, we review the current state of knowledge concerning high-elevation members of the extremophilic Cryptococcus albidus clade (now classified as the genus Naganishia). These fungi dominate eukaryotic microbial communities across the highest elevation, soil-like material (tephra) on volcanoes such as Llullaillaco, Socompa, and Saírecabur in the Atacama region of Chile, Argentina, and Bolivia. Recent studies indicate that Naganishia species are among the most resistant organisms to UV radiation, and a strain of N. friedmannii from Volcán Llullaillaco is the first organism that is known to grow during the extreme, diurnal freeze-thaw cycles that occur on a continuous basis at elevations above 6000 m.a.s.l. in the Atacama region. These and other extremophilic traits discussed in this review may serve a dual purpose of allowing Naganishia species to survive long-distance transport through the atmosphere and to survive the extreme conditions found at high elevations. Current evidence indicates that there are frequent dispersal events between high-elevation volcanoes of Atacama region and the Dry Valleys of Antarctica via "Rossby Wave" merging of the polar and sub-tropical jet streams. This dispersal hypothesis needs further verification, as does the hypothesis that Naganishia species are flexible "opportunitrophs" that can grow during rare periods of water (from melting snow) and nutrient availability (from Aeolian inputs) in one of the most extreme terrestrial habitats on Earth. [ABSTRACT FROM AUTHOR]