Box 14.9 (continued)
of Euryarchaeota, namely ANME-1, ANME-2, and
ANME-3, can mediate AOM in the marine environment
(Reeburgh 2007; Knittel and Boetius 2009 and
references therein). These groups are not monophyletic
and several sub-groups of ANME-2 with low gene
sequence similarity have also been described (Martinez
et al. 2006). The ANME-2 and ANME-1 groups are the
most frequently encountered, and are distantly or
closely related to the orders Methanosarcinales and
Methanomicrobiales. The ANME-3 group appears
mainly related to Methanococcoides spp. (Knittel
et al. 2005). The SRB partners of ANME are mostly
affiliated with the δ-Proteobacteria subdivision and are
close relatives of Desulfosarcina/Desulfococcus species
(the so-called DSS cluster; Boetius et al. 2000).
(continued)
Box 14.9 (continued)
A strong research effort during the last decade
produced significant improvements in our understanding
of the AOM process, but further highlighted variations in
the distribution, diversity, physiology, and morphology
of anaerobic methanotrophic consortia (Strous and Jetten
2004; Knittel and Boetius 2009 and references therein).
The long-term in-vitro incubation of marine sediments
showing AOM activity led to the partial enrichment of
methanotrophic consortia (Nauhaus et al. 2007) but no
defined co-culture of ANME-SRB is available to date.
Alternatively, the coupling of methane oxidation to
electron acceptors energetically more favorable than
sulfates was demonstrated. AOM coupled to the reduction of iron- or manganese-oxides, presumably mediated
by a microbial consortium as for sulfate-dependent
(continued)
CH 4 + 2 H 2 O
C O 2 + 4 H 2
HS - + 4 H 2 O
SO 4
2- + 4 H 2 + H +
Reactions
Organisms
DG
0’ (kJ)
Archaea
SRB
+ 131
- 156
HCO 3
- + HS
- + H 2 O
CH 4 + SO 4
2S :
- 25
Consortium
Archaea-SRB
Reactions
-
:
Box Scheme 14.1 AOM coupled to sulfate-reduction
Box Scheme 14.2 Alternative model for AOM coupled to sulfate-reduction
a
pentamethylicosane (PMI)
crocetane
O
O
sn-2-hydroxyarchaeol
OH
OH
b
COOH
cis-11-hexadecenoic (or16:1w5c)
COOH
11,12-methylene-hexadecanoic acid (orcy17:0w5,6)
O
OH
O
diakyl glycerol diether
Box Scheme 14.3
(a) Examples of lipid
structures produced by
ANME. (b) Examples of
lipid structures produced
by the BSR partners
of ANME
14 Biogeochemical Cycles
563
of Euryarchaeota, namely ANME-1, ANME-2, and
ANME-3, can mediate AOM in the marine environment
(Reeburgh 2007; Knittel and Boetius 2009 and
references therein). These groups are not monophyletic
and several sub-groups of ANME-2 with low gene
sequence similarity have also been described (Martinez
et al. 2006). The ANME-2 and ANME-1 groups are the
most frequently encountered, and are distantly or
closely related to the orders Methanosarcinales and
Methanomicrobiales. The ANME-3 group appears
mainly related to Methanococcoides spp. (Knittel
et al. 2005). The SRB partners of ANME are mostly
affiliated with the δ-Proteobacteria subdivision and are
close relatives of Desulfosarcina/Desulfococcus species
(the so-called DSS cluster; Boetius et al. 2000).
(continued)
Box 14.9 (continued)
A strong research effort during the last decade
produced significant improvements in our understanding
of the AOM process, but further highlighted variations in
the distribution, diversity, physiology, and morphology
of anaerobic methanotrophic consortia (Strous and Jetten
2004; Knittel and Boetius 2009 and references therein).
The long-term in-vitro incubation of marine sediments
showing AOM activity led to the partial enrichment of
methanotrophic consortia (Nauhaus et al. 2007) but no
defined co-culture of ANME-SRB is available to date.
Alternatively, the coupling of methane oxidation to
electron acceptors energetically more favorable than
sulfates was demonstrated. AOM coupled to the reduction of iron- or manganese-oxides, presumably mediated
by a microbial consortium as for sulfate-dependent
(continued)
CH 4 + 2 H 2 O
C O 2 + 4 H 2
HS - + 4 H 2 O
SO 4
2- + 4 H 2 + H +
Reactions
Organisms
DG
0’ (kJ)
Archaea
SRB
+ 131
- 156
HCO 3
- + HS
- + H 2 O
CH 4 + SO 4
2S :
- 25
Consortium
Archaea-SRB
Reactions
-
:
Box Scheme 14.1 AOM coupled to sulfate-reduction
Box Scheme 14.2 Alternative model for AOM coupled to sulfate-reduction
a
pentamethylicosane (PMI)
crocetane
O
O
sn-2-hydroxyarchaeol
OH
OH
b
COOH
cis-11-hexadecenoic (or16:1w5c)
COOH
11,12-methylene-hexadecanoic acid (orcy17:0w5,6)
O
OH
O
diakyl glycerol diether
Box Scheme 14.3
(a) Examples of lipid
structures produced by
ANME. (b) Examples of
lipid structures produced
by the BSR partners
of ANME
14 Biogeochemical Cycles
563