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Novel nuclear magnetic resonance spectroscopy methods demonstrate preferential carbon source utilization by
G L Gaines1, L Smith, E L Neidle
1Isogenetics, Inc., Chicago Technology Park, Illinois 60612, USA. glgaines@merle.acns.nwu.edu.
Journal of Bacteriology
|December 1, 1996
Summary
Novel nuclear magnetic resonance spectroscopy techniques revealed how Acinetobacter calcoaceticus degrades aromatic compounds. This soil bacterium preferentially consumes certain compounds, with cis,cis-muconate accumulation inhibiting other pathways.
Area of Science:
- Microbiology
- Biochemistry
- Spectroscopy
Background:
- Acinetobacter calcoaceticus is a soil bacterium known for its metabolic versatility.
- Understanding aromatic compound degradation is crucial for environmental bioremediation.
- Limited knowledge exists regarding microbial metabolism of multiple carbon sources simultaneously.
Purpose of the Study:
- To investigate the degradation pathways of aromatic compounds by Acinetobacter calcoaceticus using novel spectroscopy.
- To identify and quantify metabolites during bacterial growth on aromatic substrates.
- To elucidate the mechanisms of preferential substrate utilization when multiple carbon sources are present.
Main Methods:
- Utilized novel nuclear magnetic resonance (NMR) spectroscopy techniques, termed metabolic observation.
- Employed deuterated (2H) media to render bacteria spectroscopically invisible.
- Introduced natural-abundance 1H hydrogen isotopes via aromatic carbon sources for 1H NMR analysis.
- Correlated proton signals with aromatic compounds and their metabolic products.
- Constructed pathway mutants to study specific degradation steps.
Main Results:
- Identified and quantified accumulating metabolites during bacterial growth in vivo.
- Confirmed that A. calcoaceticus initiates degradation via catechol or protocatechuate, feeding into the beta-ketoadipate pathway.
- Demonstrated preferential degradation of benzoate over p-hydroxybenzoate when both were supplied.
- Discovered that cis,cis-muconate, a product of catechol ring cleavage, inhibits p-hydroxybenzoate utilization.
- Observed potential toxicity of high cis,cis-muconate levels to the bacteria.
Conclusions:
- Metabolic observation using NMR is effective for in vivo metabolic monitoring of bacterial catabolism.
- A. calcoaceticus exhibits preferential substrate utilization within the beta-ketoadipate pathway.
- cis,cis-muconate plays a regulatory role in aromatic compound degradation and may have toxic effects.