title: Microbial life at -13 °C in the brine of an ice-sealed Antarctic lake.
abstract: The permanent ice cover of Lake Vida (Antarctica) encapsulates an extreme cryogenic brine ecosystem (-13 °C; salinity, 200). This aphotic ecosystem is anoxic and consists of a slightly acidic (pH 6.2) sodium chloride-dominated brine. Expeditions in 2005 and 2010 were conducted to investigate the biogeochemistry of Lake Vida's brine system. A phylogenetically diverse and metabolically active Bacteria dominated microbial assemblage was observed in the brine. These bacteria live under very high levels of reduced metals, ammonia, molecular hydrogen (H(2)), and dissolved organic carbon, as well as high concentrations of oxidized species of nitrogen (i.e., supersaturated nitrous oxide and ∼1 mmol⋅L(-1) nitrate) and sulfur (as sulfate). The existence of this system, with active biota, and a suite of reduced as well as oxidized compounds, is unusual given the millennial scale of its isolation from external sources of energy. The geochemistry of the brine suggests that abiotic brine-rock reactions may occur in this system and that the rich sources of dissolved electron acceptors prevent sulfate reduction and methanogenesis from being energetically favorable. The discovery of this ecosystem and the in situ biotic and abiotic processes occurring at low temperature provides a tractable system to study habitability of isolated terrestrial cryoenvironments (e.g., permafrost cryopegs and subglacial ecosystems), and is a potential analog for habitats on other icy worlds where water-rock reactions may cooccur with saline deposits and subsurface oceans.
authors.affiliation: Division of Earth and Ecosystem Sciences, Desert Research Institute, Reno, NV 89512, USA. Alison.Murray@dri.edu
authors.forename: Alison E
authors.initials: AE
authors.lastname: Murray
authors.forename: Fabien
authors.initials: F
authors.lastname: Kenig
authors.forename: Christian H
authors.initials: CH
authors.lastname: Fritsen
authors.forename: Christopher P
authors.initials: CP
authors.lastname: McKay
authors.forename: Kaelin M
authors.initials: KM
authors.lastname: Cawley
authors.forename: Ross
authors.initials: R
authors.lastname: Edwards
authors.forename: Emanuele
authors.initials: E
authors.lastname: Kuhn
authors.forename: Diane M
authors.initials: DM
authors.lastname: McKnight
authors.forename: Nathaniel E
authors.initials: NE
authors.lastname: Ostrom
authors.forename: Vivian
authors.initials: V
authors.lastname: Peng
authors.forename: Adrian
authors.initials: A
authors.lastname: Ponce
authors.forename: John C
authors.initials: JC
authors.lastname: Priscu
authors.forename: Vladimir
authors.initials: V
authors.lastname: Samarkin
authors.forename: Ashley T
authors.initials: AT
authors.lastname: Townsend
authors.forename: Protima
authors.initials: P
authors.lastname: Wagh
authors.forename: Seth A
authors.initials: SA
authors.lastname: Young
authors.forename: Pung To
authors.initials: PT
authors.lastname: Yung
authors.forename: Peter T
authors.initials: PT
authors.lastname: Doran
mesh_terms: D000864:Antarctic Regions; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D003081:Cold Climate; D017753:Ecosystem; D019143:Evolution, Molecular; D007053:Ice; D060106:Lakes / Q000032:analysis / Q000382:microbiology*; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D010802:Phylogeny; D012329:RNA, Bacterial / Q000235:genetics; D012335:RNA, Ribosomal / Q000235:genetics; D014871:Water Microbiology
chemical_list: D007053:Ice; D012329:RNA, Bacterial; D012335:RNA, Ribosomal