Abstract
The cryosphere is an integral part of the global climate system and one of the major habitable ecosystems of Earth's biosphere. These permanently frozen environments harbor diverse, viable and metabolically active microbial populations that represent almost all the major phylogenetic groups. In this study, we investigated the microbial diversity in the surface snow surrounding the Concordia Research Station on the High Antarctic Plateau through a polyphasic approach, including direct prokaryotic quantification by flow cytometry and catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH), and phylogenetic identification by 16S RNA gene clone library sequencing and 454 16S amplicon pyrosequencing. Although the microbial abundance was low (<103 cells/ml of snowmelt), concordant results were obtained with the different techniques. The microbial community was mainly composed of members of the Alpha-proteobacteria class (e.g. Kiloniellaceae and Rhodobacteraceae), which is one of the most well-represented bacterial groups in marine habitats, Bacteroidetes (e.g. Cryomorphaceae and Flavobacteriaceae) and Cyanobacteria. Based on our results, polar microorganisms could not only be considered as deposited airborne particles, but as an active component of the snowpack ecology of the High Antarctic Plateau.
Highlights
The cryosphere, the portion of Earth’s biosphere where water is in solid form as snow or ice, includes vast areas of sea ice, freshwater ice, glaciers, ice sheets, snow cover and permafrost [1]
Studies on the cryosphere revealed the presence of a number of bacteria [6], which must cope with a combination of severe environmental stressors includingoligotrophic conditions, high solar UV radiation, freeze/thaw cycles, and limited liquid water [4]
Junge et al [8] reported that bacterial activity can occur at subzero temperatures
Summary
The cryosphere, the portion of Earth’s biosphere where water is in solid form as snow or ice, includes vast areas of sea ice, freshwater ice, glaciers, ice sheets, snow cover and permafrost [1]. Studies on the cryosphere revealed the presence of a number of bacteria (mainly belonging to the Bacteroidetes, Actinobacteria, Firmicutes, and Proteobacteria) [6], which must cope with a combination of severe environmental stressors including (ultra)oligotrophic conditions, high solar UV radiation, freeze/thaw cycles, and limited liquid water [4]. Carpenter et al [7] retrieved from the South Pole snow sequences related to ThermusDeinococcus-like organisms, and reported low rates of bacterial DNA and protein synthesis. Lopatina et al [9] retrieved from the snow surrounding Antarctic coastal Russian Stations some bacterial genera (Variovorax, Janthinobacterium, Pseudomonas, and Sphingomonas) that may be considered as endogenous Antarctic snow inhabitants
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