Viable halophilic microorganisms in deep ancient salt deposits

 Helga Stan-Lotter1, Sergiu Fendrihan2

1University of Salzburg, Austria; 2Romanian Bioresource Centre, Bucharest, Romania

Microbial life in subterranean halite

Significance for astrobiology carbon cycle, storage of transuranian waste and CO2

Alpine deposits, Carpathian rock salt, Others

Survival over geological times?

Swakopmund salterns (Namibia)

Locations of several Alpine Permo-Triassic salt deposits and salt mines, some of them abandoned, in Austria and Southern Germany. Salt deposits are depicted in red.

Permian salt layers (salt mine in Berchtesgaden, Germany), ca. 250 million years old

Bore cores from salt sediments (600 m below surface)

Haloarchaeal colonies on salt agar

diameter of colonies: ca. 1 cm

Halococcus salifodinae DSM 8989T (found in Alpine and Zechstein deposits)

Halococcus dombrowskiiDSM 14522T

Haloarchaeal isolates from Permo-Triassic salt

Halobacterium salinarum NRC-1 (left); Halobacterium noricense DSM 15978T, an isolate from Alpine Permian salt (right), which was found also in the WIPP site, Carlsbad, USA; bars, 1000 nm

Natronobacterium, Natrinema, Haloterrigena

Uncultured haloarchaea

Halobacterium

Halococcus

Haloferax

Uncultured haloarchaea

Halorubrum

Location of the Praid salt mine

Active salt mines in Romania

Extraterrestrial halite

SNC-Meteorites (from Mars; Shergotty, Nakhla Chassigny)Murchison meteorite (from asteroid belt)Monahans meteorite (from asteroid belt)salt pools on the surface of Marsocean on the Jovian moon Europa

Enceladus (moon of Saturn) geysirs

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Red and blue sodium chloride crystalsin the Monahans meteorite. Each picture is 1 mm in width.

Haloarchaea embedded in halite crystals

How might haloarchaea survive in ancient salt sediments ?

Pre-stained cells of Hbt. salinarum in halite fluid inclusions. Low magnification (left) and high magnification of an individual fluid inclusion (right)

Halobacterium salinarum NRC-1

normal growth: rods (A); after embedding in fluid inclusions: spheres (B – G)

Reduction of water activity (aw) leads to formation of spheres, provided multiplegenomes are present (Zerulla & Soppa, 2014)

Astrobiology: Viable haloarchaea survived geological times periods in ancient salt sediments, possibly in a stable resting state (spheres)

Carbon interactions: Halococcus species and maybe other haloarchaea are present in the oceans; a RuBisCo-like gene is present in haloarchaea, but CO2 fixation has not been clarified. Clues from ancient communities?

Other aspects: usage of salt deposits/mines as storage for transuranian waste, also CO2 was proposed- thus, it is mandatory to study properties of indigenous halophilic communities

Significance