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Cultivation and characterization of the bacterial assemblage of epsomic Basque Lake, BC

Authors
  • Crisler, James D.1
  • Chen, Fei2
  • Clark, Benton C.3
  • Schneegurt, Mark A.1
  • 1 Wichita State University, Department of Biological Sciences, 26, 1845 Fairmount, Wichita, KS, 67260, USA , Wichita (United States)
  • 2 NASA, Planetary Protection Group, Jet Propulsion Laboratory, Pasadena, CA, USA , Pasadena (United States)
  • 3 Space Science Institute, Boulder, CO, USA , Boulder (United States)
Type
Published Article
Journal
Antonie van Leeuwenhoek
Publisher
Springer-Verlag
Publication Date
Feb 08, 2019
Volume
112
Issue
7
Pages
1105–1119
Identifiers
DOI: 10.1007/s10482-019-01244-0
Source
Springer Nature
Keywords
License
Yellow

Abstract

Athalassohaline waters that are rich in divalent ions are good analogues for the chemical environments of Mars and the ocean worlds. Sulfate salts, along with chlorides, are important in Mars regolith with Ca, Fe, Mg, and Na counterions. Certain lakes in the Pacific Northwest are saturated with MgSO4 as epsomite. Here we report on the microbial community of Basque Lake, BC, a group of playas that is saturated with MgSO4. More than 60 bacterial isolates were obtained from Basque Lake soils by enrichment culture and repetitive streak-plating using media containing 10% (~ 1.7 M) NaCl or 50% (~ 2 M) MgSO4. Most of the isolates (~ 75%) were Gram-positive, motile, and produced endospores. Isolates related to Marinococcus halophilus and Virgibacillus marismortui dominated the collection. Halomonas and Salinivibrio were Gram-negative genera found at Basque Lake. Nearly all of the Basque Lake isolates grew at 50% MgSO4, with 65% growing at 60% MgSO4. Several isolates could grow in saturated (67%) MgSO4 (aw = 0.90). All of the isolates grew at 10% NaCl with 70% growing at 20% salinity (~ 3.5 M NaCl; aw = 0.82). Basque Lake isolates grew better at basic pH than acidic pH, with 80% growing at pH 9 and 30% growing at pH 10. Only 20% of the isolates grew at pH 5. Numerical taxonomy dendrograms based on 44 phenetic characteristics showed a strong correspondence to phylogenetic trees constructed from 16S rRNA gene sequences. Pyrosequencing of 16S rRNA gene sequences from direct DNA extracts of Basque Lake soils recovered predominantly Proteobacteria (60%), Firmicutes (11%), and unclassified bacteria (27%). Microbes capable of growth under the extreme chemical conditions of Mars are a particular concern for forward planetary protection should they contaminate a spacecraft.

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