25th International Meeting on Organic Geochemistry IMOG 2011

P-247
Carbon capture by soil chemoautotrophs
Kris Hart 1 , Brian Moran 1 , Chris Allen 2 , André Simpson 3 , Brian Kelleher 1
1 Dublin City University, Dublin, Ireland, 2 Queens University Belfast, Belfast, Ireland, 3 University of Toronto,
Toronto, Canada (corresponding author:brian.kelleher@dcu.ie)
Soil Organic Matter (SOM) is the most complicated
biomaterial on Earth. It has been shown to contain
significantly more carbon than is currently present in
the atmosphere (approx twice as much) [1, 2]. It has
been recently reported that humic material in SOM is
a highly complex mixture of microbial and plant
biopolymers and not a distinct chemical fraction as
previously thought [2]. Furthermore, it has been
reported that the microbial biomass contribution to
SOM is not comprised of mainly humic materials and
that in fact the contribution to SOM by soil
microorganisms has been seriously underestimated
[3]. Therefore, the question arises if we underestimate
microbial biomass in soil do we also underestimate
carbon uptake by soil microbes? The presented
material herein is part of a project to develop a
methodology to combine ecological studies with
molecular characteristics using soil chemoautotrophic
bacteria in vivo and measurements of CO2 uptake
using a stable carbon isotope ( 13 C). Soil microcosms
were developed in an environmental incubation
chamber under short term incubations (≤24 hr).
Detection of the labelled biomass within the SOM
fraction was performed using GCMS-IRMS. IRMS
analysis revealed isotopic enrichment of lipids up to
91%, which can be directly affiliated to atmospheric
CO2 capture. High resolution infra-red detection of
internal CO2 concentrations indicate that maximum
uptakes rates of 1574 mg CO2/Ha/100 hr were
incorporated into biomass. Complimentary analysis
using 13 C solid state HR-MAS-NMR confirmed
enrichment had taken place leading to the detection
of complex biomaterial such as carbohydrates and
proteins. Preliminary identification of CO2 assimilating
microbes was performed using ultra-centrifugation
stable isotope probing (SIP) to separate the ‗heavy‘
labelled DNA fraction from the total DNA. The isolated
13 C-DNA was then cloned into E.coli using standard
molecular biological techniques and the identification
of Acidothiobacillus ferrooxidans and Thiobacillus
denitrificans was made by comparison to the BLAST
DNA sequence database.
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