title: A microbial oasis in the hypersaline Atacama subsurface discovered by a life detector chip: implications for the search for life on Mars.
abstract: The Atacama Desert has long been considered a good Mars analogue for testing instrumentation for planetary exploration, but very few data (if any) have been reported about the geomicrobiology of its salt-rich subsurface. We performed a Mars analogue drilling campaign next to the Salar Grande (Atacama, Chile) in July 2009, and several cores and powder samples from up to 5 m deep were analyzed in situ with LDChip300 (a Life Detector Chip containing 300 antibodies). Here, we show the discovery of a hypersaline subsurface microbial habitat associated with halite-, nitrate-, and perchlorate-containing salts at 2 m deep. LDChip300 detected bacteria, archaea, and other biological material (DNA, exopolysaccharides, some peptides) from the analysis of less than 0.5 g of ground core sample. The results were supported by oligonucleotide microarray hybridization in the field and finally confirmed by molecular phylogenetic analysis and direct visualization of microbial cells bound to halite crystals in the laboratory. Geochemical analyses revealed a habitat with abundant hygroscopic salts like halite (up to 260 g kg(-1)) and perchlorate (41.13 μg g(-1) maximum), which allow deliquescence events at low relative humidity. Thin liquid water films would permit microbes to proliferate by using detected organic acids like acetate (19.14 μg g(-1)) or formate (76.06 μg g(-1)) as electron donors, and sulfate (15875 μg g(-1)), nitrate (13490 μg g(-1)), or perchlorate as acceptors. Our results correlate with the discovery of similar hygroscopic salts and possible deliquescence processes on Mars, and open new search strategies for subsurface martian biota. The performance demonstrated by our LDChip300 validates this technology for planetary exploration, particularly for the search for life on Mars.
authors.affiliation: Department of Molecular Evolution, Centro de Astrobiología (INTA-CSIC), Madrid, Spain. parrogv@inta.es
authors.forename: Victor
authors.initials: V
authors.lastname: Parro
authors.forename: Graciela
authors.initials: G
authors.lastname: de Diego-Castilla
authors.forename: Mercedes
authors.initials: M
authors.lastname: Moreno-Paz
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Blanco
authors.forename: Patricia
authors.initials: P
authors.lastname: Cruz-Gil
authors.forename: José A
authors.initials: JA
authors.lastname: Rodríguez-Manfredi
authors.forename: David
authors.initials: D
authors.lastname: Fernández-Remolar
authors.forename: Felipe
authors.initials: F
authors.lastname: Gómez
authors.forename: Manuel J
authors.initials: MJ
authors.lastname: Gómez
authors.forename: Luis A
authors.initials: LA
authors.lastname: Rivas
authors.forename: Cecilia
authors.initials: C
authors.lastname: Demergasso
authors.forename: Alex
authors.initials: A
authors.lastname: Echeverría
authors.forename: Viviana N
authors.initials: VN
authors.lastname: Urtuvia
authors.forename: Marta
authors.initials: M
authors.lastname: Ruiz-Bermejo
authors.forename: Miriam
authors.initials: M
authors.lastname: García-Villadangos
authors.forename: Marina
authors.initials: M
authors.lastname: Postigo
authors.forename: Mónica
authors.initials: M
authors.lastname: Sánchez-Román
authors.forename: Guillermo
authors.initials: G
authors.lastname: Chong-Díaz
authors.forename: Javier
authors.initials: J
authors.lastname: Gómez-Elvira
mesh_terms: D001105:Archaea / Q000302:isolation & purification*; D001419:Bacteria / Q000302:isolation & purification*; D015415:Biomarkers / Q000032:analysis; D015374:Biosensing Techniques; D002677:Chile; D003889:Desert Climate; D017753:Ecosystem; D018535:Mars; D059013:Microbial Consortia; D054712:Salinity
chemical_list: D015415:Biomarkers