25th International Meeting on Organic Geochemistry IMOG 2011

P-181
Bacterial wax esters in fluvial sediments from the Danube River
(Republic of Serbia)
Jürgen Köster 1 , Vesna Miciš 2 , Michael A. Kruge 3 , Thilo Hofmann 2
1 Institute of Chemistry and Biology of the Marine Environment, Carl von Ossietzky University, Oldenburg,
Germany, 2 Department of Environmental Geosciences, University of Vienna, Vienna, Austria, 3 Department
of Earth and Environmental Studies, Montclair State University, Montclair (NJ), United States of America
(corresponding author:juergen.koester@icbm.de)
Extracts of fluvial sediments from the Serbian part of
the Danube River contain wax esters with an unusual,
complex distribution. The carbon number range from
C28 to C36 and the high proportion of iso- and anteisomethyl-branched
constituents strongly point to a
bacterial origin.
Carbon number distributions of the wax esters show
two distinct patterns: First, wax esters with even
numbers are dominated by compounds with two
straight chains that dominate over combinations with
methyl branched moieties (n-/n-: 63 %, n-/br-: 23 %,
br-/br-: 14 %); second, in case of odd carbon
numbers: combinations with straight and methylbranched
isomers prevail (n-/n-: 27 %, n-/br-: 64 %,
br-/br-: 9 %). Each peak comprises several (up to 6)
isomers that arise from different combinations of
chain lengths.
Overall, the fatty acid pool involved in wax ester
formation contains mainly C16 and C15 fatty acids (30
% and 27 %, respectively) followed by C14 (10%), C17
(9 %) and C18 (5 %) compounds.
In addition to the saturated wax esters,
monounsaturated ones occur. They are dominated by
n-/n- C32 and C34 compounds with minor contributions
of n-/i- and n-/ai isomers with odd carbon numbers:
Wax esters with a phytyl chain were found in
combination with n-alkyl chains from C14 to C18 (with
dominance of n-C16). Also phytyl phytanoate is
present.
The elution order and retention times agree well with
calculated relative retention indices for methylated
compounds and values reported for long-chain wax
esters (Moldowan et al. 2002, J. Chrom. A 952).
The highest wax ester content was found in a sample
characterized by particularly abundant phytadienes
and n-C17 alkane indicating a high primary productivity
(Miciš et al. 2011, Sci. Tot. Env. 409). Literature
reports on similar wax ester distributions are sparse
(e.g. Cranwell 1984, Org. Geochem. 6) and the exact
origin of these compounds is not known yet. The
distributions of isomers suggest that the wax esters
are preferentially synthesized from indigenous
compounds typical for bacterial cell wall constituents,
rather than from external, assimilated compounds.
TIC
m/z 452 (C 30)
m/z 466 (C 31)
4
*
12
3
5
m/z 480 (C 32)
6
m/z 494 (C 33)
58 60 62 64 66 68 70 72 74 76 78
Retention time (min)
Partial total ion chromatogram of a wax ester fraction
and selected chromatograms of molecular ions of wax
esters. Asterix: n-C30 and n-C32 monounsaturated
wax esters, P: C34 and C36 wax esters with phytyl
chains, Pp: phytyl phytanoate; elution order of isomer
mixtures (1-6): i-/i-, i-/ai-, ai-/ai-, n-/i-, n-/ai-, n-/n-.
P
*
P
Pp
321