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Terrestrial models for extraterrestrial life: methanogens and halophiles at Martian temperatures

Published online by Cambridge University Press:  08 August 2006

I.N. Reid
Affiliation:
Maryland Astrobiology Consortium, USA Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA e-mail: inr@stsci.edu
W.B. Sparks
Affiliation:
Maryland Astrobiology Consortium, USA Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA e-mail: inr@stsci.edu
S. Lubow
Affiliation:
Maryland Astrobiology Consortium, USA Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA e-mail: inr@stsci.edu
M. McGrath
Affiliation:
Maryland Astrobiology Consortium, USA Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA e-mail: inr@stsci.edu Marshall Spaceflight Center, Huntsville, AL 35812, USA
M. Livio
Affiliation:
Maryland Astrobiology Consortium, USA Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA e-mail: inr@stsci.edu
J. Valenti
Affiliation:
Maryland Astrobiology Consortium, USA Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA e-mail: inr@stsci.edu
K.R. Sowers
Affiliation:
Maryland Astrobiology Consortium, USA University of Maryland Biotechnology Institute, Center of Marine Biotechnology, Baltimore, MD 21202, USA e-mail: dassarma@umbi.umd.edu
H.D. Shukla
Affiliation:
Maryland Astrobiology Consortium, USA University of Maryland Biotechnology Institute, Center of Marine Biotechnology, Baltimore, MD 21202, USA e-mail: dassarma@umbi.umd.edu
S. MacAuley
Affiliation:
Maryland Astrobiology Consortium, USA University of Maryland Biotechnology Institute, Center of Marine Biotechnology, Baltimore, MD 21202, USA e-mail: dassarma@umbi.umd.edu
T. Miller
Affiliation:
Maryland Astrobiology Consortium, USA University of Maryland Biotechnology Institute, Center of Marine Biotechnology, Baltimore, MD 21202, USA e-mail: dassarma@umbi.umd.edu
R. Suvanasuthi
Affiliation:
Maryland Astrobiology Consortium, USA University of Maryland Biotechnology Institute, Center of Marine Biotechnology, Baltimore, MD 21202, USA e-mail: dassarma@umbi.umd.edu
R. Belas
Affiliation:
Maryland Astrobiology Consortium, USA University of Maryland Biotechnology Institute, Center of Marine Biotechnology, Baltimore, MD 21202, USA e-mail: dassarma@umbi.umd.edu
A. Colman
Affiliation:
Maryland Astrobiology Consortium, USA University of Maryland Biotechnology Institute, Center of Marine Biotechnology, Baltimore, MD 21202, USA e-mail: dassarma@umbi.umd.edu
F.T. Robb
Affiliation:
Maryland Astrobiology Consortium, USA University of Maryland Biotechnology Institute, Center of Marine Biotechnology, Baltimore, MD 21202, USA e-mail: dassarma@umbi.umd.edu
P. DasSarma
Affiliation:
Maryland Astrobiology Consortium, USA University of Maryland Biotechnology Institute, Center of Marine Biotechnology, Baltimore, MD 21202, USA e-mail: dassarma@umbi.umd.edu
J.A. Müller
Affiliation:
Maryland Astrobiology Consortium, USA University of Maryland Biotechnology Institute, Center of Marine Biotechnology, Baltimore, MD 21202, USA e-mail: dassarma@umbi.umd.edu Department of Biology, Morgan State University, Baltimore, MD 21215, USA
J.A. Coker
Affiliation:
Maryland Astrobiology Consortium, USA University of Maryland Biotechnology Institute, Center of Marine Biotechnology, Baltimore, MD 21202, USA e-mail: dassarma@umbi.umd.edu
R. Cavicchioli
Affiliation:
Maryland Astrobiology Consortium, USA School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia
F. Chen
Affiliation:
Maryland Astrobiology Consortium, USA University of Maryland Biotechnology Institute, Center of Marine Biotechnology, Baltimore, MD 21202, USA e-mail: dassarma@umbi.umd.edu
S. DasSarma
Affiliation:
Maryland Astrobiology Consortium, USA University of Maryland Biotechnology Institute, Center of Marine Biotechnology, Baltimore, MD 21202, USA e-mail: dassarma@umbi.umd.edu

Abstract

Cold environments are common throughout the Galaxy. We are conducting a series of experiments designed to probe the low-temperature limits for growth in selected methanogenic and halophilic Archaea. This paper presents initial results for two mesophiles, a methanogen, Methanosarcina acetivorans, and a halophile, Halobacterium sp. NRC-1, and for two Antarctic cold-adapted Archaea, a methanogen, Methanococcoides burtonii, and a halophile, Halorubrum lacusprofundi. Neither mesophile is active at temperatures below 5 °C, but both cold-adapted microorganisms show significant growth at sub-zero temperatures (−2 °C and −1 °C, respectively), extending previous low-temperature limits for both species by 4–5 °C. At low temperatures, both H. lacusprofundi and M. burtonii form multicellular aggregates, which appear to be embedded in extracellular polymeric substances. This is the first detection of this phenomenon in Antarctic species of Archaea at cold temperatures. The low-temperature limits for both psychrophilic species fall within the temperature range experienced on present-day Mars and could permit survival and growth, particularly in sub-surface environments. We also discuss the results of our experiments in the context of known exoplanet systems, several of which include planets that intersect the Habitable Zone. In most cases, those planets follow orbits with significant eccentricity, leading to substantial temperature excursions. However, a handful of the known gas giant exoplanets could potentially harbour habitable terrestrial moons.

Type
Research Article
Copyright
2006 Cambridge University Press

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