25th International Meeting on Organic Geochemistry IMOG 2011

P-056
Detection of microbial biomass in subseafloor sediments by
pyrolysis-GC/MS
Rong Zhu, Gerard J.M. Versteegh, Kai-Uwe Hinrichs
MARUM - Center for Marine Environmental Sciences, University of Bremen, Organic Geochemistry Group,
D-28334 Bremen, Germany (corresponding author:rongzhu@uni-bremen.de)
Pyrolysis-GC/MS is an excellent approach to
rapidly generate low-molecular fingerprints from
organic macromolecules. It has been successfully
applied to characterize microorganisms and
differentiate between them [e.g., 1, 2]. These previous
studies on microbes principally used ratios of
diagnostic fragments and multivariate analyses (e.g.,
principal components analysis) to differentiate
between the taxa [e.g., 3, 4]. Considering this, we
want to explore if we can use pyrolysis-GC/MS as a
method to rapidly screen for the presence of labile
macromolecules associated with living microbes in
the deep biosphere.
To adapt this method to the analysis of
sedimentary matrices, we first pyrolyzed cells of
different archaeal and bacterial lineages (Fig.1 A, B)
as well as reference substances and model
compounds to obtain a fingerprint for living microbial
biomass. Pyrolysis products derived from proteins,
carbohydrates and nucleic acids generally dominated
the pyrolysates. Although the relative distributions of
these compounds varied between the strains, no
specific archaeal or bacterial fingerprint could be
identified so far. By pyrolyzing surface sediments from
the Peru Margin (Fig.1 C) we tested to what extent
the fingerprint of microbial biomass could be
recovered from the benthic ecosystem. As expected
some nitrogen-bearing fragments derived from
proteins, amino sugars and nucleic acids occur both
in microbial cultures and surface sediments (Fig. 1).
Although in the surface sediments, proteins, amino
sugars and nucleic acids may also be derived from
fresh organic matter from the overlying water column,
such contribution is not expected to play a role in
more deeply buried sediment. Momentarily we are
testing to what extent we can follow our target
compounds down into the deep biosphere.
Furthermore, we are generating a calibration curve as
basis for estimating sedimentary microbe
concentrations from pyrolysates. Preliminary analyses
show that at around 100 m below the sea floor signals
can be still detected. We will further explore the
occurrence of living microbial biomass in deeply
buried sediments. We also intend to apply this
approach for off-line isotope ratio mass spectrometry
(IRMS) to track the carbon substrates and nutrient
cycling of subsurface microbial communities.
Fig.1. Characteristic partial pyrolysis-GC/MS
chromatograms of Acetobacterium woodii (A),
Methanosarcina barkeri (B), and a surface sediment
from the Peru Margin (C). (1: nitrile derivatives; 2:
pyridine and derivatives; 3: acetic acid; 4: pyrrole and
derivatives; 5: furan derivatives; 6: acetamide; 7:
phenol and derivatives; 8: indole)
References
[1] Irwin, W.J. (1979b) J. Anal. Appl. Pyrolysis. 1, 89-
122.
[2] Snyder, A.P. et al. (2004) Anal. Chem. 76, 6492-
6499
[3] Goodacre, R. and Kell, D.B. (1996) Curr. Opin.
Biotechnol. 7, 20-28.
[4] Barshick, S.A., Wolf D.A. and Vass A.A. (1999)
Anal. Chem. 71, 633-641.
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