title: Biomarkers and Metabolic Patterns in the Sediments of Evolving Glacial Lakes as a Proxy for Planetary Lake Exploration.
abstract: Oligotrophic glacial lakes in the Andes Mountains serve as models to study the effects of climate change on natural biological systems. The persistent high UV regime and evolution of the lake biota due to deglaciation make Andean lake ecosystems potential analogues in the search for life on other planetary bodies. Our objective was to identify microbial biomarkers and metabolic patterns that represent time points in the evolutionary history of Andean glacial lakes, as these may be used in long-term studies as microscale indicators of climate change processes. We investigated a variety of microbial markers in shallow sediments from Laguna Negra and Lo Encañado lakes (Región Metropolitana, Chile). An on-site immunoassay-based Life Detector Chip (LDChip) revealed the presence of sulfate-reducing bacteria, methanogenic archaea, and exopolymeric substances from Gammaproteobacteria. Bacterial and archaeal 16S rRNA gene sequences obtained from field samples confirmed the results from the immunoassays and also revealed the presence of Alpha-, Beta-, Gamma-, and Deltaproteobacteria, as well as cyanobacteria and methanogenic archaea. The complementary immunoassay and phylogenetic results indicate a rich microbial diversity with active sulfate reduction and methanogenic activities along the shoreline and in shallow sediments. Sulfate inputs from the surrounding volcanic terrains during deglaciation may explain the observed microbial biomarker and metabolic patterns, which differ with depth and between the two lakes. A switch from aerobic and heterotrophic metabolisms to anaerobic ones such as sulfate reduction and methanogenesis in the shallow shores likely reflects the natural evolution of the lake sediments due to deglaciation. Hydrodynamic deposition of sediments creates compartmentalization (e.g., sediments with different structure and composition surrounded by oligotrophic water) that favors metabolic transitions. Similar phenomena would be expected to occur on other planetary lakes, such as those of Titan, where watery niches fed by depositional events would be surrounded by a "sea" of hydrocarbons. Key Words: Glacier lakes-Sedimentation-Prokaryotic metabolisms and biomarkers-Deglaciation-Life detection-Planetary exploration. Astrobiology 18, 586-606.
authors.affiliation: 1 Department of Molecular Evolution, Centro de Astrobiología (INTA-CSIC) , Madrid, Spain .
authors.forename: Víctor
authors.initials: V
authors.lastname: Parro
authors.affiliation: 1 Department of Molecular Evolution, Centro de Astrobiología (INTA-CSIC) , Madrid, Spain .
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Blanco
authors.affiliation: 1 Department of Molecular Evolution, Centro de Astrobiología (INTA-CSIC) , Madrid, Spain .
authors.forename: Fernando
authors.initials: F
authors.lastname: Puente-Sánchez
authors.affiliation: 1 Department of Molecular Evolution, Centro de Astrobiología (INTA-CSIC) , Madrid, Spain .
authors.forename: Luis A
authors.initials: LA
authors.lastname: Rivas
authors.affiliation: 1 Department of Molecular Evolution, Centro de Astrobiología (INTA-CSIC) , Madrid, Spain .
authors.forename: Mercedes
authors.initials: M
authors.lastname: Moreno-Paz
authors.affiliation: 2 Centro de Biotecnología "Profesor Alberto Ruiz," Universidad Católica del Norte , Antofagasta, Chile .
authors.forename: Alex
authors.initials: A
authors.lastname: Echeverría
authors.affiliation: 2 Centro de Biotecnología "Profesor Alberto Ruiz," Universidad Católica del Norte , Antofagasta, Chile .
authors.forename: Guillermo
authors.initials: G
authors.lastname: Chong-Díaz
authors.affiliation: 2 Centro de Biotecnología "Profesor Alberto Ruiz," Universidad Católica del Norte , Antofagasta, Chile .
authors.forename: Cecilia
authors.initials: C
authors.lastname: Demergasso
authors.affiliation: 3 The SETI Institute , Carl Sagan Center, Mountain View, California, and NASA Ames Research Center, Moffett Field, California, USA .
authors.forename: Nathalie A
authors.initials: NA
authors.lastname: Cabrol
mesh_terms: D001105:Archaea / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D001419:Bacteria / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D044822:Biodiversity; D015415:Biomarkers / Q000032:analysis; D019015:Geologic Sediments / Q000382:microbiology*; D060106:Lakes / Q000382:microbiology*; D010802:Phylogeny; D016083:Planets; D012336:RNA, Ribosomal, 16S / Q000302:isolation & purification
chemical_list: D015415:Biomarkers; D012336:RNA, Ribosomal, 16S