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Appl. Environ. Microbiol., 04 1996, 1188-1196, Vol 62, No. 4
HR Beller, AM Spormann, PK Sharma, JR Cole and M Reinhard
A novel sulfate-reducing bacterium isolated from fuel-contaminated
subsurface soil, strain PRTOL1, mineralizes toluene as the sole electron
donor and carbon source under strictly anaerobic conditions. The
mineralization of 80% of toluene carbon to CO2 was demonstrated in
experiments with [ring-U-14C]toluene; 15% of toluene carbon was converted
to biomass and nonvolatile metabolic by-products, primarily the former. The
observed stoichiometric ratio of moles of sulfate consumed per mole of
toluene consumed was consistent with the theoretical ratio for
mineralization of toluene coupled with the reduction of sulfate to hydrogen
sulfide. Strain PRTOL1 also transforms o- and p-xylene to metabolic
products when grown with toluene. However, xylene transformation by PRTOL1
is slow relative to toluene degradation and cannot be sustained over time.
Stable isotope-labeled substrates were used in conjunction with gas
chromatography-mass spectrometry to investigate the by-products of toluene
and xylene metabolism. The predominant by-products from toluene, o-xylene,
and p-xylene were benzylsuccinic acid, (2-methylbenzyl)succinic acid, and
4-methylbenzoic acid (or p-toluic acid), respectively. Metabolic
by-products accounted for nearly all of the o-xylene consumed. Enzyme
assays indicated that acetyl coenzyme A oxidation proceeded via the carbon
monoxide dehydrogenase pathway. Compared with the only other reported
toluene- degrading, sulfate-reducing bacterium, strain PRTOL1 is distinct
in that it has a novel 16S rRNA gene sequence and was derived from a
freshwater rather than marine environment.
Copyright © 1996, American Society for Microbiology
Isolation and characterization of a novel toluene-degrading, sulfate- reducing bacterium
Department of Civil Engineering, Stanford University, California 94305- 4020, USA.
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