• Main Authors: Mary Ann Liebert, Brian Popp
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Ice Shelf; Iceland
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.596.8842; http://www.soest.hawaii.edu/GG/FACULTY/POPP/Gaidos et al. 2004 Astrobiology.pdf

We describe a viable microbial community in a subglacial lake within the Grímsvötn vol-canic caldera, Iceland. We used a hot water drill to penetrate the 300-m ice shelf and retrieved lake water and volcanic tephra sediments. We also acquired samples of borehole water be-fore and after penetration to the lake, overlying glacial ice and snow, and water from a nearby subaerial geothermal lake for comparative analyses. Lake water is at the freezing point and fresh (total dissolved solids 260 mg L1). Detectable numbers of cells were found in sam-ples of the lake water column and tephra sediments: 2 104 ml1 and 4 107 g1, respec-tively. Plate counts document abundant cold-adapted cultivable organisms in the lake water, but not in the borehole (before penetration) or glacial ice. Denaturing gradient gel elec-trophoresis (DGGE) of 16S rRNA gene fragments amplified from genomic DNA extracted from Grímsvötn samples indicates that the lake community is distinct from the assemblages of organisms in borehole water (before penetration) and the overlying ice and snow. Se-quencing of selected DGGE bands revealed that many sequences are highly similar to known psychrophilic organisms or cloned DNA from other cold environments. Significant uptake of 14C-labeled bicarbonate occurred in dark, low-temperature incubations of lake water samples, indicating the presence of autotrophs. Acetylene reduction assays under similar incubation conditions showed no significant nitrogen fixation potential by lake water samples. This may be a consequence of the inhibition of diazotrophy by nitrogen in the lake. Key Words: Ex-treme environments—Microbial ecology—Subglacial lakes. Astrobiology 4, 327–344. 327