Phylogenetic Diversity Analysis of Subterranean Hot Springs in Iceland

Abstract

Geothermal energy has been harnessed and used for domestic heating in Iceland. In wells that are typically drilled to a depth of 1,500 to 2,000 m, the temperature of the source water is 50 to 130°C. The bottoms of the boreholes can therefore be regarded as subterranean hot springs and provide a unique opportunity to study the subterranean biosphere. Large volumes of geothermal fluid from five wells and a mixture of geothermal water from 50 geothermal wells (hot tap water) were sampled and concentrated through a 0.2-m-pore-size filter. Cells were observed in wells RG-39 (91.4°C) and MG-18 (71.8°C) and in hot tap water (76°C), but no cells were detected in wells SN-4, SN-5 (95 to 117°C), and RV-5 (130°C). Archaea and Bacteria were detected by whole-cell fluorescent in situ hybridization. DNAs were extracted from the biomass, and small-subunit rRNA genes (16S rDNAs) were amplified by PCR using primers specific for the Archaea and Bacteria domains. The PCR products were cloned and sequenced. The sequence analysis showed 11 new operational taxonomic units (OTUs) out of 14, 3 of which were affiliated with known surface OTUs. Samples from RG-39 and hot tap water were inoculated into enrichment media and incubated at 65 and 85°C. Growth was observed only in media based on geothermal water. 16S rDNA analysis showed enrichments dominated with Desulfurococcales relatives. Two strains belonging to Desulfurococcus mobilis and to the Thermus/Deinococcus group were isolated from borehole RG-39. The results indicate that subsurface volcanic zones are an environment that provides a rich subsurface for novel thermophiles.

Evidence of global-scale aeolian dispersal and endemism in isolated geothermal microbial communities of Antarctica

“…A full-length sequence was also reconstructed for the novel, dominant Archaeon observed in the amplicon data set. This particular Archaeon was most closely related (94% identity) to a single clone (GI# 14028778) from a subterranean hot spring in Iceland 29 and shared no more than 87.1% identity to any other sequence in the NCBI database. Phylogenetic analysis of this full-length 16S rRNA gene grouped it with Crenarchaeota and Thaumarchaeota, specifically suggesting that it is a deep-branching relative of the Thaumarchaeota (Fig.…”

Persephonella hydrogeniphila sp. nov., a novel thermophilic, hydrogen-oxidizing bacterium from a deep-sea hydrothermal vent chimney

“…Thermophilic hydrogen-and/or sulfur-oxidizing bacteria of the order Aquificales are widely distributed in diverse hot environments such as terrestrial geothermal fields, shallowand deep-sea hydrothermal vent systems and deep subsurface hot aquifer environments (Kawasumi et al, 1984;Kryukov et al, 1984;Huber et al, 1992 Huber et al, , 1998Shima & Suzuki, 1993;Hugenholtz et al, 1998;L'Haridon et al, 1998; Reysenbach et al, 2000a, b, c;Marteinsson et al, 2001;Takacs et al, 2001;Takai et al, 2001 Takai et al, , 2002. Members of the Aquificales are thought to have an impact on biogeochemical processes in these ecosystems (Kristjansson et al, 1985;Harmsen et al, 1997; Götz et al, 2002).…”

“…The last lineage largely consisted of a number of previously uncultivated environmental rDNA clones obtained from global terrestrial hot-spring environments such as in Yellowstone National Park (Hugenholtz et al, 1998;Reysenbach et al, 2000a), Iceland (Skirnisdottir et al, 2000;Takacs et al, 2001) and Japan (Yamamoto et al, 1998), and in subterranean hot springs (Marteinsson et al, 2001), and even in deep-sea hydrothermal vent systems (Reysenbach et al, 2000b, c). Recently, however, several representative strains of this lineage such as Hydrogenothermus (Stöhr et al, 2001), Persephonella (Reysenbach et al, 2000a;Götz et al, 2002) and a potentially new genus of strains (Takai et al, 2002) have been successfully isolated from shallow and deep marine hydrothermal vent environments and from a subsurface hot aquifer environment.…”

Sulfurihydrogenibium subterraneum gen. nov., sp. nov., from a subsurface hot aquifer

“…Culture-resistant phylotypes of thermophiles within the order Aquificales are potentially prevalent in microbial communities occurring in a certain temperature range (50-90 uC) in habitats in global terrestrial hot spring environments such as in Yellowstone National Park (Hugenholtz et al, 1998;Reysenbach et al, 1994Reysenbach et al, , 2000a, Iceland (Skirnisdottir et al, 2000;Takacs et al, 2001) and Japan (Yamamoto et al, 1998), in subterranean hot springs (Marteinsson et al, 2001) and even in deep-sea hydrothermal vent systems (Reysenbach et al, 2000b). These phylotypes form a clade, probably corresponding to a novel family, that is separate from the HydrogenobaculumAquifex-Hydrogenobacter-Thermocrinis lineage (family Aquificaceae) within the order Aquificales (Takai et al, 2002).…”