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Methanogenic toluene metabolism: community structure and intermediates
S Jane Fowler1, Xiaoli Dong, Christoph W Sensen
1Petroleum Microbiology Research Group, Department of Biological Sciences, University of Calgary, Calgary, AB, Canada T2N 1N4.
Environmental Microbiology
|November 2, 2011
Summary
This study reveals how microbes break down toluene anaerobically. Toluene is primarily activated by fumarate addition, with some evidence for alternative pathways under specific conditions.
Area of Science:
- Environmental microbiology
- Biogeochemistry
- Anaerobic biodegradation
Background:
- Toluene biodegradation under anaerobic conditions is crucial for environmental remediation.
- Previous studies suggest fumarate addition or unknown mechanisms for toluene transformation.
Purpose of the Study:
- Investigate the mechanism of syntrophic toluene metabolism in a methanogenic enrichment culture.
- Identify key microbial players and metabolic pathways involved in toluene breakdown.
Main Methods:
- Enrichment culture from a contaminated aquifer.
- Pyrosequencing of 16S rDNA for microbial community analysis.
- Isotope studies using (13)C(7) toluene and (18)O-H(2)O.
- Detection of the BssA gene fragment.
Main Results:
- Methane production from toluene reached 72-79% of theoretical yield.
- Transient accumulation of benzylsuccinate and benzoate confirmed fumarate addition pathway.
- BssA gene fragment supported fumarate addition as a toluene activation mechanism.
- Formation of hydroxylated intermediates was observed but did not originate from water, with abiotic formation noted.
Conclusions:
- The dominant mechanism for toluene activation in this syntrophic consortium is fumarate addition, likely catalyzed by Clostridiales.
- Alternative metabolic pathways may exist but are less significant or influenced by abiotic factors.
- This research elucidates a key microbial process in the anaerobic degradation of aromatic hydrocarbons.
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