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Methanogenesis under Extreme Environmental Conditions in Permafrost Soils: A Model for Exobiological Processes?
D. Wagner1, S. Kobabe1, E.-M. Pfeiffer2 and H.-W. Hubberten1
1Alfred Wegener Institute for Polar and Marine Research, Potsdam, Germany2Institute of Soil Science, University of Hamburg, Hamburg, Germany
ARC 915 + DAPIARC 915 + DAPI
ARC 915 + EUB 338 mixARC 915 + EUB 338 mix
ARC 915ARC 915
The evolution of life on Earth had already started 3.8 Ga ago, when living conditions on Mars were similar to those on early Earth. Assuming that first life on both planets was determined by complex microbial communities, the Martian life must have adapted to drastically changing
environmental conditions or become extinct again. One possibility for survival of Martian primitive life might be subsurface lithoautotrophicecosystems. Comparable environments exist in permafrost regions on Earth. Therefore, terrestrial permafrost, in which microorg-anisms have survived for several million years, is considered to be a model for extraterrestrial analogues.
IINTRODUCTIONNTRODUCTION
MMETHANOGENIC ETHANOGENIC AARCHAEARCHAEA
Responsible for the microbial methane production (methanogenesis) is a small group of highly specialised microorganisms, called methanogenic archaea. They are regarded as strictly anaerobic microbes, which can grow and survive only under anoxic conditions. They are characterised by lithoautotrophic growth, whereby energy is
gained by the oxidation of hydrogen and carbon dioxide can be used as the only carbon source. Because of the specific adaptations of methanogenic archaea to conditions like those on early Earth (e.g. no oxygen, no or little organic substrates) and their phylogenetic origin, they are considered as key-organisms in astrobiological research .
MMETHANOGENESISETHANOGENESIS
Major landmarks of bio-logical
evolution on Earth
0 20 40 60 80
0
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time [h]
CH4
0
1
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9
temperature
tem
pera
ture
[°C]
de
pth
[cm
]
300
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50
0
0,00 0,02 0,04 0,06 0,5 1,5
300
250
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0acetate
0,00 0,02 0,04 0,06 0,5 1,5
hydrogen
core LD-01-1
active layer
CCONCLUSIONONCLUSION
contact: [email protected]
Martian surface and terrestrial permafrost areas
show similar mor-phological
structures.
Northern Martian hemisphere (NASA)
Lena Delta, Siberia (AWI)
The presented results show that methanogenic archaea are suitable key-organisms for further studies about adaptation strategies and long-term survival in extreme environments. Microbiological studies in
combination with geochemical and physical analysis can give insights into early stages of life in terrestrial permafrost, which can be used as a model for exobiological processes.
Studies of CH4 production in the active layer showed methanogenesisat in situ temperatures between 0.6 and 1.2 °C as well as at –3 °C (0.1 – 11.4 nmol CH4 h-1 g-1) and –6 °C (0.08 – 4.3 nmol CH4 h-1 g-1). In Holocene permafrost deposits high CH4 concentrations were proven and methanogenesis could be initiated after thawing of the sediments.
The results indicated the existence of a methanogenic community , which has well adapted to the low in situ temperature of permafrost.
800
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200
100
0
0 2500 5000 7500 0 2500 5000 7500
Samoylov
(72°22N/126°29E)
de
pth
[cm
]
Kurungnakh(72°19N/126°13E)
1
2
1 2
3
3
In situ CH4 production in the boundary layer
to the permafrost at 1 °C
CH4 production at subzero temperatures with H2/CO2 as a substrate
CH4 concentration in Holocene permafrost
deposits of the Lena Delta
CH4 production
potential at 5 °C with
acetate or
hydrogen as substrate after
thawing of the Holocene
sediments
Aggregates of methanogenic
archaea in permafrost soils
detected by fluorescence in
situ hybridisation. The
aggregate formation could
serve as protection against
extreme habitate conditions.
CH
4[p
pm
]
0 100 200 300 400 500
0
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0
150
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- 3 °C
CH4
time [h]
- 6 °C
CH4
CH
4[p
pm
]C
H4
[pp
m]
CH4 [ppm]
CH4 production [nmol h-1 g-1]
4 H4 H22 + CO+ CO22
CHCH44 + H+ H22OO
500 nm
MethanosarcinaMethanosarcina
specspec..
ClimateClimate historyhistory of of earlyearly Earth and MarsEarth and Mars
EarthEarth MarsMars
AtmosphereAtmosphere
Pressure
Temperature
Duration
HydrosphereHydrosphere
BiosphereBiosphere
CO2, N2, H2O CO2, N2, ?
≥≥≥≥ 1 atm ≈≈≈≈ 1 atm
≥≥≥≥ 0 °C ≈≈≈≈ 0 °C
until today first Ga
oceans rivers, lakes ?
since > 3.8 Ga ???
McKay and Davis,
1991
10 m
4,0
3,0
2,0
1,0
0,0
4,5
Origin of life
Origin of modern eukaryotes
Origin of metazoans
Age of dinosaurs
20%
10%
1%
0,1%
Chemical
evolution
Origin of cyanobacteria
Microbialdiversification
Archaea
Bacteria
Oxygenated
environment
Morphological
evolution ofmetazoans
Eukarya
anoxic
O2concentration
time before present
[billions of years]