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approximately 1 h. Reactant materials (50 mg) were sealed into the gold capsule,
after welding both end of the cell by utilizing a tungsten inert-gas arc welder
(Lampert PUK3) with high precision welding capabilities (0.3 mm) that minimize
heat generation along the weld. The capsules are hosted in small volume (~30 ml)
pressure vessels to minimize the duration of quenching to ambient conditions
during experiment termination (Cody et al.
2001
). After quenching, the gold tube
reactors were removed from the high-pressure apparatus and rinsed with methanol
and then dried.
Modern and heated
Oscillatoria
samples were pyrolysed at Carnegie using a
CDS 1000 Pyroprobe by heating at 615 °C for 10 s. Compound detection and iden-
tifi cation were performed using on line GC-MS in full scan mode with a Hewlett
Packard HP6890 gas chromatograph interfaced to a HP 6890 mass selective detec-
tor. GC was performed with a Supelco MD-5S column (30 m, 0.25 mm I.D.,
0.25 ml fi lm thickness) using He as the carrier gas. The oven was programmed
from 50 (held 1 min) to 300 °C (held 28 min) at 5 °C min
−1
. The source was oper-
ated in the electron ionization (EI) mode with 70 eV ionization energy at 250 C.
The mass selective detector scan rate was 0.80 s/decade over a mass range of
50-500 Da with an inter-scan delay of 0.20 s.
Results and Discussion
A solvent-insoluble residue was recovered after the hydrothermal experiment on
bacteria that was subsequently subjected to thermal extraction at 310 °C to further
remove any volatile components and then analysed by pyrolysis-gas chromatography-
mass spectrometry, at 615 °C, to evaluate the macromolecular composition.
Py-GC-MS is commonly used to characterise solvent insoluble sedimentary organic
carbon, that is, kerogen (Larter and Horsfi eld
1993
; de Leeuw et al.
2006
; de Leeuw
2007
). The unheated precursor bacterium was also similarly extracted and then ana-
lyzed by Py-GC-MS revealing the biopolymer and lipid distribution. The unheated
bacterial pyrolysate consists predominantly of small molecules derived unambigu-
ously from protein (alkyl benzenes, alkyl phenols, indoles, cyanobenzenes), poly-
saccharides (furans and levoglucosan) and lipids. Of these compound classes, the
lipids consist predominantly of fatty acids with up to 18 carbon atoms (Fig.
10.1
),
consistent with distributions of these molecules from the soluble extracts of
Oscillatoria
sp. (Oren et al.
1985
). Analysis of the heated material reveals that the
biopolymeric composition has drastically changed and most biopolymers detected
in the modern bacteria are chemically transformed to a different macromolecular
composition. Py-GC-MS after solvent and thermal extraction reveals a macromol-
ecule with signifi cant aliphatic carbon, represented by the alkane, alkene homo-
logues in the gas chromatogram analysis distinct up to C
18.
Alkane-alkene doublets
such as these are ubiquitous in pyrolysates derived from ancient sediments and
refl ect the aliphatic nature of ancient refractory organic carbon (Larter and Horsfi eld
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