25th International Meeting on Organic Geochemistry IMOG 2011

P-440
Estimation of endospore numbers in marine sediment samples
by quantification of dipicolinic acid
Marieke Sieverding 1 , Bert Engelen 1 , Henrik Sass 2 , Barbara Scholz-Böttcher 1 , Heribert
Cypionka 1 , Jürgen Rullkötter 1
1 Institute of Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky University of
Oldenburg, P.O. Box 2503, D-26111 Oldenburg, Germany, 2 School of Earth, Ocean and Planetary Sciences,
Cardiff University, Cardiff CF10 3YE, United Kingdom (corresponding author:marieke.sieverding@unioldenburg.de)
For more than 20 years, the scientific drilling
community has studied microbial life in deeply buried
sediments [1,2]. During these studies, prokaryotes
were detected even at 1600 mbsf [3]. Extrapolation of
direct counts of microbial cells leads to the estimate
that one tenth to one third of the world‘s living
biomass may be stored in the marine sub-seafloor
biosphere [4]. Until today, it is unclear as to what
extent these prokaryotes are active, since
fluorescence dyes, like acridine orange or DAPI, do
not discriminate between metabolically active,
dormant or dead cells. These dyes even stain
endospores. In this study we show that in marine
sediments endospores contribute up to 19 % to the
total cell numbers at some tens of meters of depth.
Depth (m)
0,1
1
10
100
1000
3 4 5 6 7 8 9 10 11
Log 10 (spores g -1 sediment)
Fig 1: Depth distribution of endospores in tidal flat sediments
(black data points) and in sediments from ODP Leg 201
(green squares) in comparison with the depth distribution of
prokaryotes in the deep biosphere (red line) determined by
[5] (in log10[cells cm -3 sediment]; red dashed lines: 95 %
upper and lower prediction limits).
Dipicolinic acid (DPA), which is a major component of
endospores, was used to quantify endospores in up to
20 m long sediment cores collected from a tidal flat
area near Spiekeroog Island, NW Germany, as well
as in several sediment samples from ODP Leg 201.
DPA contents were determined fluorimetrically using
a highly sensitive post-column complexation HPLC
approach [6]. DPA contents ranged from 0.004 to
1.7 nmol DPA g -1 sediment dry weight, corresponding
to 1.6 × 10 4 to 7.7 × 10 6 spores g -1 sediment dry
weight (Fig. 1). For conversion of dipicolinic acid
contents into endospore numbers an average DPA
content of 2.24 × 10 -16 mol per endospore was
assumed. The endospore depth profiles of the tidal
flat sediments were non-linear, but reflected the
vertical changes in lithology. The highest endospore
numbers were found in muddy samples, while
significantly lower numbers were detected in sandy
Janssand
ODP-Proben
sediments. The contribution of endospore numbers to
total cell counts increased with sediment depth
reaching up to 10 % of total cell counts in the deepest
layer. In sediment samples from Leg 201 the
contribution of endospores to total cell numbers is
even higher, ranging from 3 to 19 %. The relative
increase of endospore contribution to total cell
numbers with sediment age is explained by the
longevity of endospores, whereas numbers of
vegetative cells are expected to decrease more
rapidly due to starvation (Fig. 1).
References
[1] Whelan et al., 1986. Initial Reports of the Deep
Sea Drilling Project 96, 6578-6583.
[2] Parkes et al., 1994. Nature 371, 410-413.
[3] Roussel et al., 2008. Science 320, 1046.
[4] Whitman et al., 1998. Proceedings of the
National Academy of Sciences of the USA 95,
6578-6583.
[5] Parkes et al., 2000. Hydrogeology Journal 8, 11-
28.
[6] Fichtel et al., 2007. Journal of Microbiological
Methods 70, 319-327.
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