Methanotrophic Proteobacteria

Methylocella

Methanogenic Archaea

Methylocapsa acidiphiia

Methylocystis Methylosinus alpha-Pmteobacteria

Methanobacteriales

Methanococcales

Methanopyrus kandleri

ANME3

Methanol

Methanolobus/Methanohaiophylus ^coccoides' Methanosarcina

ARC1

0.10

Methanobacteriales

Methanococcales

ARC1

Praying Hands Cross And Bible

/ ANME2A saetaeeae

■ Methylotbermus thermal:!

Methylohalobius

Methanomicrobiales

ANMEIGBa Methylocaldum

/ ANME2A saetaeeae

ANME1-AT

ANME1A ANME1B

Methylocella

■ Methylotbermus thermal:!

Methanomicrobiales

ANMEIGBa Methylocaldum

ANME1-AT

ANME1A ANME1B

alpha-Pmteobacteria

Methylococcus

Methylosphaera hansonii Methylomonas

Methylococcus gamma-Proteobacteria

Methylomicrobium

Methylosarcina Methylobacter Methylobacter Crenothrix poiyspora

Methylosphaera hansonii Methylomonas

Clonothrixfusca

Methylobacter psychrophilus. Mb. tundripaludum unc. Mb. sp. permafrost (Lena-Delta) unc. Mb. sp. permafrost soil (Lena-Delta)

unc. Mb. sp. permafrost soil (Lena-Delta)

Fig. 15.3 Phylogenetic relation (based on 16S rRNA gene sequences) of methanogenic archaea and aerobic methanotrophic bacteria. Grey squares illustrate groups including sequences from Arctic tundra environments. Trees represent maximum likelihood trees using the PhyML algorithm (Guindon and Gascuel, 2003) and the ARB software package permafrost soils. Recent studies on perennially frozen permafrost deposits from the Lena Delta (Siberia) revealed significant amounts of methane which could be attributed to in situ activity of methanogenic archaea (Wagner et al. 2007). Another study on frozen ground on Ellesmere Island reported an archaeal community composed of 61% Euryarchaeota (methane-producing archaea) and 39% Crenarchaeota, suggesting the presence of a diverse archaeal population also in the perennially frozen sediments (Steven et al. 2007; see also Chap. 5).

Methanosarcina sp. SMA-21, which is closely related to Methanosarcina mazei, was recently isolated from a Siberian permafrost soil in the Lena Delta. The organism grows well at 28°C and slowly at low temperatures (4°C and 10°C) with H2/ CO2 (80:20, v/v, pressurised at 150 kPa) as substrate. The cells grow as cocci, with a diameter of 1-2 |im. Cell aggregates were regularly observed (Fig. 15.4a). Methanosarcina SMA-21 is characterized by an extreme tolerance to very low temperatures (-78.5°C), high salinity (up to 6 M NaCl), starvation, desiccation and oxygen exposure (Morozova and Wagner 2007). Furthermore, this archaeon survived for 3 weeks under simulated thermo-physical Martian conditions (Morozova et al. 2007; see also Chap. 21).

Sma Methane

Fig. 15.4 Methane-cycling microorganisms isolated from permafrost environments. a Methanosarcina sp. SMA-21 (D. Wagner and D. Morozova, AWI; bar: 10 |im). b permafrost strain SMA-23 (D. Wagner and D. Morozova, AWI). c Methylobacter tundripaludum (Wartiainen et al. 2006a). d Methylocystis rosea (Wartiainen et al. 2006b)

Fig. 15.4 Methane-cycling microorganisms isolated from permafrost environments. a Methanosarcina sp. SMA-21 (D. Wagner and D. Morozova, AWI; bar: 10 |im). b permafrost strain SMA-23 (D. Wagner and D. Morozova, AWI). c Methylobacter tundripaludum (Wartiainen et al. 2006a). d Methylocystis rosea (Wartiainen et al. 2006b)

Methanogenic activity has been observed at low in situ temperatures, with rates of up to 39 nmol CH4 h-1 g-1 soil in the active layer of permafrost (Wagner et al. 2003; H0j et al. 2005; Metje and Frenzel 2007). The highest activities were thereby measured in the coldest zones of the profiles. Furthermore, it could be shown that methane production is limited rather by the quality of soil organic carbon than by the in situ temperature (Wagner et al. 2005; Ganzert et al. 2007). Another important factor affecting methanogenic communities in permafrost soils is the water regime. Along a natural soil moisture gradient, changes in archaeal community composition were observed, which suggest that the differences in these communities were responsible for the large-scale variations in methane emissions observed with changes in soil hydrology (H0j et al. 2006).

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