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Low Pressure Tolerance by Methanogens in an Aqueous Environment: Implications for Subsurface Life on Mars

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The low pressure at the surface of Mars (average: 6 mbar) is one potentially biocidal factor that any extant life on the planet would need to endure. Near subsurface life, while shielded from ultraviolet radiation, would also be exposed to this low pressure environment, as the atmospheric gas-phase pressure increases very gradually with depth. Few studies have focused on low pressure as inhibitory to the growth or survival of organisms. However, recent work has uncovered a potential constraint to bacterial growth below 25 mbar. The study reported here tested the survivability of four methanogen species (Methanothermobacter wolfeii, Methanosarcina barkeri, Methanobacterium formicicum, Methanococcus maripaludis) under low pressure conditions approaching average martian surface pressure (6 mbar – 143 mbar) in an aqueous environment. Each of the four species survived exposure of varying length (3 days – 21 days) at pressures down to 6 mbar. This research is an important stepping-stone to determining if methanogens can actively metabolize/grow under these low pressures. Additionally, the recently discovered recurring slope lineae suggest that liquid water columns may connect the surface to deeper levels in the subsurface. If that is the case, any organism being transported in the water column would encounter the changing pressures during the transport.
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ASTROBIOLOGY
Low Pressure Tolerance by Methanogens in an Aqueous
Environment: Implications for Subsurface Life on Mars
R. L. Mickol
1
&T. A. Kral
1,2
Received: 13 June 2016 / Accepted: 5 September 2016 /
Published online: 23 September 2016
#Springer Science+Business Media Dordrecht 2016
Abstract The low pressure at the surface of Mars (average: 6 mbar) is one potentially biocidal
factor that any extant life on the planet would need to endure. Near subsurface life, while shielded
from ultraviolet radiation, would also be exposed to this low pressure environment, as the
atmospheric gas-phase pressure increases very gradually with depth. Few studies have focused
on low pressure as inhibitory to the growth or survival of organisms. However, recent work has
uncovered a potential constraint to bacterial growth below 25 mbar. The study reported here tested
the survivability of four methanogen species (Methanothermobacter wolfeii,Methanosarcina
barkeri,Methanobacterium formicicum,Methanococcus maripaludis) under low pressure con-
ditions approaching average martian surface pressure (6 mbar 143 mbar) in an aqueous
environment. Each of the four species survived exposure of varying length (3 days 21 days)
at pressures down to 6 mbar. This research is an important stepping-stone to determining if
methanogens can actively metabolize/grow under these low pressures. Additionally, the recently
discovered recurring slope lineae suggest that liquid water columns may connect the surface to
deeper levels in the subsurface. If that is the case, any organism being transported in the water
column would encounter the changing pressures during the transport.
Keywords Methanogens .Mars .Methane .Low pressure .Survival
Orig Life Evol Biosph (2017) 47:511532
DOI 10.1007/s11084-016-9519-9
*R. L. Mickol
rmickol@uark.edu
T. A. Kral
tkral@uark.edu
1
Arkansas Center for Space and Planetary Sciences, University of Arkansas, Stone House North, 332
N. Arkansas Ave, Fayetteville, AR 72701, USA
2
Department of Biological Sciences, Science and Engineering 601, University of Arkansas,
Fayetteville, AR 72701, USA
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
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