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Nat Ecol Evol. 2019 Nov;3(11):1552-1561. doi: 10.1038/s41559-019-1005-0. Epub 2019 Oct 28.

Hyperdiverse archaea near life limits at the polyextreme geothermal Dallol area.

Author information

1
Ecologie Systématique Evolution, CNRS, Université Paris-Sud, Université Paris-Saclay, AgroParisTech, Orsay, France.
2
Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, CNRS, Sorbonne Université, Muséum National d'Histoire Naturelle, Paris, France.
3
Instituto Geológico y Minero de España, Palma de Mallorca, Spain.
4
Departamento de Ecología, Universidad Autónoma de Madrid, Madrid, Spain.
5
Ecologie Systématique Evolution, CNRS, Université Paris-Sud, Université Paris-Saclay, AgroParisTech, Orsay, France. puri.lopez@u-psud.fr.

Abstract

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 Mg2+/Ca2+-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.

PMID:
31666740
PMCID:
PMC6837875
[Available on 2020-04-28]
DOI:
10.1038/s41559-019-1005-0
[Indexed for MEDLINE]
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