25th International Meeting on Organic Geochemistry IMOG 2011

O-76
Carbon fluxes in phylogenetically distinct AOM performing
microbial consortia
Sebastian Bertram 1 , Martin Blumenberg 2 , Richard Seifert 1 , Martin Krüger 3 , Walter
Michaelis 1
1 Institute of Biogeochemistry and Marine Chemistry, University of Hamburg, Hamburg, Germany,
2 Geobiology Group, Geoscience Centre (GZG), University of Göttingen, Göttingen, Germany, 3 Section
Geomicrobiology, Federal Institute for Geosciences and Natural Resources, Hannover, Germany
(corresponding author:walter.michaelis@zmaw.de)
The anaerobic oxidation of methane (AOM) coupled
to sulphate-reduction is an important process in
marine settings. However, it is still not completely
understood, and is considered as a reverse process
of methanogenesis. An unknown electron shuttle
transfers the energy between syntrophic anaerobic
methane-oxidising archaea (ANME) and sulphatereducing
bacteria (SRB). Moreover, while
metagenomic investigations by several groups
demonstrate a high microbial diversity in AOMsettings,
the physiological capabilities of such
involved organisms are widely unknown.
One promising approach to get information on
metabolic capabilities of microbial systems is
compound specific stable isotope probing with carbon
isotopically labelled substrates, since none of the
involved organisms has been isolated in pure culture
so far.
Previous in-vitro studies with labelled methane and
bicarbonate revealed uptake into archaeal and
bacterial lipids and indicate autotrophic growth of SRB
[1, 2].
We extended our previous incubation experiments,
among others, with isotopically labelled acetate and
methanol to investigate further heterotrophic
capabilities within two different AOM communities.
These mat samples are dominated by ANME-1 or
ANME-2, respectively. They emerged under similar,
anoxic environmental conditions from the Black Sea
(Krüger et al., 2008). Our results showed an
unexpected high 13 C-uptake into archaeal lipids with
labelled methanol as substrate. Assimilation rates of
methanol-derived carbon were especially high for
sn2-hydroxyarchaeol. In contrast to experiments with
other substrates, a significant
13 C-uptake from
methanol into archaeal lipids also occurred in the
absence of methane. This suggests a strong
adaptation of involved archaea to methylotrophic
substrates. We also observed high rates of
autotrophic and heterotrophic methanogenesis. By
analysing the isotopic enrichments of methane, we
found individual impacts of different (isotopically
labelled) substrates on methanogenesis. We detected
specific lipid biomarkers for methylotrophic bacteria in
these consortia and elevated assimilation rates with
methanol indicate a homoacetogenic metabolism of
involved source organisms. Our work further suggests
chemoorganotrophic and AOM independent
autotrophic metabolic life styles of associated
bacteria. These new data reveal much higher
physiological capabilities of AOM-communities than
previously shown. Especially the so far unknown
methylotrophic physiology of anaerobic
methanotrophs or other archaea present in recent and
ancient sediments is of great importance and subject
of forthcoming studies.
References:
[1] Blumenberg M., Seifert R., Nauhaus K., Pape T.,
and Michaelis W. (2005) AEM 71:4345-4351.
[2] Wegener, G., Niemann H., Elvert M., Hinrichs K.-
U., and Boetius A. (2008) EMI 10:2287–2298.
[3] Krüger, M., Blumenberg M., Kasten K., Wieland A.,
Layla K., Klock J.-H., Michaelis W., and Seifert R.
(2008) EMI 10:1934-1947.
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