Characterization of halophiles in natural MgSO4 salts and laboratory enrichment samples: Astrobiological implications for Mars

Foster, Ian S., King, Penelope L., Hyde, Brendt C. and Southam, Gordon (2010) Characterization of halophiles in natural MgSO4 salts and laboratory enrichment samples: Astrobiological implications for Mars. Planetary and Space Science, 58 4: 599-615. doi:10.1016/j.pss.2009.08.009

Author Foster, Ian S.
King, Penelope L.
Hyde, Brendt C.
Southam, Gordon
Title Characterization of halophiles in natural MgSO4 salts and laboratory enrichment samples: Astrobiological implications for Mars
Journal name Planetary and Space Science   Check publisher's open access policy
ISSN 0032-0633
Publication date 2010-03
Year available 2010
Sub-type Article (original research)
DOI 10.1016/j.pss.2009.08.009
Open Access Status
Volume 58
Issue 4
Start page 599
End page 615
Total pages 17
Place of publication Kidlington, Oxford, United Kingdom
Publisher Pergamon Press
Collection year 2010
Language eng
Formatted abstract
The presence of sulfate salts and limited subsurface water (ice) on Mars suggests that any liquid water on Mars today will occur as (magnesium) sulfate-rich brines in regions containing sources of magnesium and sulfur. The Basque Lakes of British Columbia, Canada, represent a hypersaline terrestrial analogue site, which possesses chemical and physical properties similar to those observed on Mars. The Basque Lakes also contain diverse halophilic organisms representing all three Kingdoms of life, growing in surface and near-subsurface environments. Of interest from an astrobiological perspective, crushed magnesium sulfate samples that were analyzed using a modified Lowry protein assay contained biomass in every crystal inspected, with biomass values from 0.078 to 4.21 mgbiomass/gsalt; average=0.74±0.7 mgbiomass/gsalt. Bacteria and Archaea cells were easily observed even in low-biomass samples using light microscopy, and bacteria trapped within magnesium sulfate crystals were observed using confocal microscopy. Regions within the salt also contained bacterial pigments, e.g., carotenoids, which were separate from the cells, indicating that cell lysis might have occurred during entrapment within the salt matrix. These biosignatures, cells, and any ‘soluble’ organic constituents were primarily found trapped within fluid inclusions or fluid-filled void spaces between intergrown crystals. Diffuse reflectance infrared Fourier transform spectroscopy (reflectance IR) analysis of enrichment cultures, containing cyanobacteria, Archaea, or dissimilatory sulfate-reducing bacteria, highlighted molecular biosignature features between 550–1650 and 2400–3000 cm−1. Spectra from natural salts demonstrated that we can detect biomass within salt crystals using the most sensitive biosignatures, which are the 1530–1570 cm−1, C–N, N–H, –COOH absorptions and the 1030–1050 cm−1 C–OH, C–N, PO43− bond features. The lowest detection limit for a biosignature absorption feature using reflectance IR was with a natural sample that possessed 0.78 mgbiomass/gsalt. In a model cell, i.e., a 0.5 by 1 μm bacillus, this biomass value corresponds to approximately 7.8×108 cells/gsalt. Based on its ability to detect biomass entrapped within natural sulfate salts, reflectance IR may make an effective remote-sensing tool for finding enrichments of organic carbon within outcrops and surficial sedimentary deposits on Mars. 
Keyword Halophiles
Infrared Spectroscopy
Confocal microscopy
Raman Spectroscopy
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Earth Sciences Publications
Version Filter Type
Citation counts: TR Web of Science Citation Count  Cited 12 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 14 times in Scopus Article | Citations
Google Scholar Search Google Scholar
Created: Mon, 24 Jun 2013, 15:09:27 EST by System User on behalf of School of Earth Sciences