Open AccessHyperdiverse archaea near life limits at the polyextreme geothermal Dallol area
Author(s) -
Jodie Belilla,
David Moreira,
Ludwig Jardillier,
Guillaume Reboul,
Karim Benzerara,
José María López-García,
Paola Bertolino,
Ana Isabel López-Archilla,
Purificación LópezGarcía
Publication year - 2019
Publication title -
nature ecology and evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.822
H-Index - 57
ISSN - 2397-334X
DOI - 10.1038/s41559-019-1005-0
Subject(s) - archaea , extreme environment , halophile , abiotic component , abiogenesis , extremophile , astrobiology , biology , ecology , chemistry , microorganism , bacteria , paleontology
Microbial life has adapted to various individual extreme conditions; yet, organisms simultaneously adapted to very low pH, high salt and high temperature are unknown. We combined environmental 16S/18S ribosomal RNA gene metabarcoding, cultural approaches, fluorescence-activated cell sorting, scanning electron microscopy and chemical analyses to study samples along such unique polyextreme gradients in the Dallol-Danakil area in Ethiopia. We identified two physicochemical barriers to life in the presence of surface liquid water defined by (1) high chaotropicity-low water activity in Mg 2+ /Ca 2+ -dominated brines and (2) hyperacidity-salt combinations (pH ~0/NaCl-dominated salt saturation). When detected, life was dominated by highly diverse ultrasmall archaea that were widely distributed across phyla with and without previously known halophilic members. We hypothesize that a high cytoplasmic K + -level was an original archaeal adaptation to hyperthermophily, subsequently exapted during several transitions to extreme halophily. We detect active silica encrustment/fossilization of cells but also abiotic biomorphs of varied chemistry. Our work helps circumscribing habitability and calls for cautionary interpretations of morphological biosignatures on Earth and beyond.