title: Connecting biodiversity and potential functional role in modern euxinic environments by microbial metagenomics.
abstract: Stratified sulfurous lakes are appropriate environments for studying the links between composition and functionality in microbial communities and are potentially modern analogs of anoxic conditions prevailing in the ancient ocean. We explored these aspects in the Lake Banyoles karstic area (NE Spain) through metagenomics and in silico reconstruction of carbon, nitrogen and sulfur metabolic pathways that were tightly coupled through a few bacterial groups. The potential for nitrogen fixation and denitrification was detected in both autotrophs and heterotrophs, with a major role for nitrogen and carbon fixations in Chlorobiaceae. Campylobacterales accounted for a large percentage of denitrification genes, while Gallionellales were putatively involved in denitrification, iron oxidation and carbon fixation and may have a major role in the biogeochemistry of the iron cycle. Bacteroidales were also abundant and showed potential for dissimilatory nitrate reduction to ammonium. The very low abundance of genes for nitrification, the minor presence of anammox genes, the high potential for nitrogen fixation and mineralization and the potential for chemotrophic CO2 fixation and CO oxidation all provide potential clues on the anoxic zones functioning. We observed higher gene abundance of ammonia-oxidizing bacteria than ammonia-oxidizing archaea that may have a geochemical and evolutionary link related to the dominance of Fe in these environments. Overall, these results offer a more detailed perspective on the microbial ecology of anoxic environments and may help to develop new geochemical proxies to infer biology and chemistry interactions in ancient ecosystems.
authors.affiliation: Integrative Freshwater Ecology Group, Center of Advanced Studies of Blanes-Spanish Council for Research (CEAB-CSIC), Blanes, Girona, Spain.
authors.forename: Tomàs
authors.initials: T
authors.lastname: Llorens-Marès
authors.affiliation: Informatics Group, J Craig Venter Institute, San Diego, CA, USA.
authors.forename: Shibu
authors.initials: S
authors.lastname: Yooseph
authors.affiliation: Informatics Group, J Craig Venter Institute, Rockville, MD, USA.
authors.forename: Johannes
authors.initials: J
authors.lastname: Goll
authors.affiliation: Microbial and Environmental Genomics Group, J Craig Venter Institute, San Diego, CA, USA.
authors.forename: Jeff
authors.initials: J
authors.lastname: Hoffman
authors.affiliation: Integrative Freshwater Ecology Group, Center of Advanced Studies of Blanes-Spanish Council for Research (CEAB-CSIC), Blanes, Girona, Spain.
authors.forename: Maria
authors.initials: M
authors.lastname: Vila-Costa
authors.affiliation: 1] Water Quality and Microbial Diversity, Catalan Institute for Water Research (ICRA), Girona, Spain [2] Group of Molecular Microbial Ecology, Institute of Aquatic Ecology, University of Girona, Girona, Spain.
authors.forename: Carles M
authors.initials: CM
authors.lastname: Borrego
authors.affiliation: Microbial and Environmental Genomics Group, J Craig Venter Institute, San Diego, CA, USA.
authors.forename: Chris L
authors.initials: CL
authors.lastname: Dupont
authors.affiliation: Integrative Freshwater Ecology Group, Center of Advanced Studies of Blanes-Spanish Council for Research (CEAB-CSIC), Blanes, Girona, Spain.
authors.forename: Emilio O
authors.initials: EO
authors.lastname: Casamayor
mesh_terms: D000641:Ammonia / Q000378:metabolism; D001105:Archaea / Q000235:genetics; D001419:Bacteria / Q000235:genetics*; D044822:Biodiversity; D002244:Carbon / Q000378:metabolism; D057486:Carbon Cycle / Q000235:genetics; D058440:Denitrification / Q000235:genetics; D060106:Lakes / Q000737:chemistry / Q000382:microbiology*; D056186:Metagenomics / Q000379:methods*; D009566:Nitrates / Q000378:metabolism; D058465:Nitrification; D009584:Nitrogen / Q000378:metabolism; D009586:Nitrogen Fixation / Q000235:genetics; D010084:Oxidation-Reduction; D013030:Spain; D013455:Sulfur / Q000378:metabolism; D014871:Water Microbiology
chemical_list: D009566:Nitrates; D013455:Sulfur; D002244:Carbon; D000641:Ammonia; D009584:Nitrogen