| Summary: | Microbial community profiles of recently formed hot spring systems ranging in temperatures from 57°C to 100°C and pH values from 2 to 4 in Hveragerði (Iceland) were analyzed with PhyloChip G3 technology. In total, 1173 bacterial operational taxonomic units (OTUs) spanning 576 subfamilies and 38 archaeal OTUs covering 32 subfamilies were observed. As expected, the hyperthermophilic (100°C) spring system exhibited both low microbial biomass and diversity when compared to thermophilic (60°C) springs. Ordination analysis revealed distinct bacterial and archaeal diversity in geographically distinct hot springs. Slight variations in temperature (from 57°C to 64°C) within the interconnected pools led to a marked fluctuation in microbial abundance and diversity. Correlation and PERMANOVA tests provided evidence that temperature was the key environmental factor responsible for microbial community dynamics, while pH, H_(2)S, and SO_2 influenced the abundance of specific microbial groups. When archaeal community composition was analyzed, the majority of detected OTUs correlated negatively with temperature, and few correlated positively with pH. Key Words: Microbial diversity—PhyloChip G3—Acidophilic—Thermophilic—Hot springs—Iceland. Astrobiology 14, xxx–xxx. © 2014 Mary Ann Liebert, Inc. Online Ahead of Print: March 3, 2014. Part of the research described in this study was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. A. Probst's contribution was supported by the German National Academic Foundation (Studienstiftung des deutschen Volkes). J. Krebs's participation was funded by a Caltech Amgen Scholars Fellowship awarded in 2011. The authors are grateful to the Coordination Action for Research Activities on life in Extreme Environments (CAREX) project funded by the European Commission. A special thanks to N. Walter, European Science Federation, for supporting P. Vaishampayan's travel to Iceland. We ...
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