title: Microbial community of the deep-sea brine Lake Kryos seawater-brine interface is active below the chaotropicity limit of life as revealed by recovery of mRNA.
abstract: Within the complex of deep, hypersaline anoxic lakes (DHALs) of the Mediterranean Ridge, we identified a new, unexplored DHAL and named it 'Lake Kryos' after a nearby depression. This lake is filled with magnesium chloride (MgCl2 )-rich, athalassohaline brine (salinity > 470 practical salinity units), presumably formed by the dissolution of Messinian bischofite. Compared with the DHAL Discovery, it contains elevated concentrations of kosmotropic sodium and sulfate ions, which are capable of reducing the net chaotropicily of MgCl2 -rich solutions. The brine of Lake Kryos may therefore be biologically permissive at MgCl2 concentrations previously considered incompatible with life. We characterized the microbiology of the seawater-Kryos brine interface and managed to recover mRNA from the 2.27-3.03 M MgCl2 layer (equivalent to 0.747-0.631 water activity), thereby expanding the established chaotropicity window-for-life. The primary bacterial taxa present there were Kebrit Deep Bacteria 1 candidate division and DHAL-specific group of organisms, distantly related to Desulfohalobium. Two euryarchaeal candidate divisions, Mediterranean Sea Brine Lakes group 1 and halophilic cluster 1, accounted for > 85% of the rRNA-containing archaeal clones derived from the 2.27-3.03 M MgCl2 layer, but were minority community-members in the overlying interface-layers. These findings shed light on the plausibility of life in highly chaotropic environments, geochemical windows for microbial extremophiles, and have implications for habitability elsewhere in the Solar System.
authors.affiliation: CNR, Institute for Coastal Marine Environment, Messina, 98122, Italy.
authors.forename: Michail M
authors.initials: MM
authors.lastname: Yakimov
authors.forename: Violetta
authors.initials: V
authors.lastname: La Cono
authors.forename: Gina L
authors.initials: GL
authors.lastname: Spada
authors.forename: Giovanni
authors.initials: G
authors.lastname: Bortoluzzi
authors.forename: Enzo
authors.initials: E
authors.lastname: Messina
authors.forename: Francesco
authors.initials: F
authors.lastname: Smedile
authors.forename: Erika
authors.initials: E
authors.lastname: Arcadi
authors.forename: Mireno
authors.initials: M
authors.lastname: Borghini
authors.forename: Manuel
authors.initials: M
authors.lastname: Ferrer
authors.forename: Phillippe
authors.initials: P
authors.lastname: Schmitt-Kopplin
authors.forename: Norbert
authors.initials: N
authors.lastname: Hertkorn
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Cray
authors.forename: John E
authors.initials: JE
authors.lastname: Hallsworth
authors.forename: Peter N
authors.initials: PN
authors.lastname: Golyshin
authors.forename: Laura
authors.initials: L
authors.lastname: Giuliano
mesh_terms: D001105:Archaea / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D001419:Bacteria / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D060106:Lakes / Q000382:microbiology*; D008522:Mediterranean Sea; D059013:Microbial Consortia / Q000502:physiology*; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D054712:Salinity; D012492:Salts / Q000032:analysis; D012623:Seawater / Q000382:microbiology*; D012965:Sodium Chloride / Q000032:analysis; D014871:Water Microbiology
chemical_list: D012333:RNA, Messenger; D012336:RNA, Ribosomal, 16S; D012492:Salts; D012965:Sodium Chloride