Evidence for acetyl coenzyme A and cinnamoyl coenzyme A in the anaerobic toluene mineralization pathway in Azoarcus tolulyticus Tol-4

Abstract

A toluene-degrading denitrifier, Azoarcus tolulyticus Tol-4, was one of eight similar strains isolated from three petroleum-contaminated aquifer sediments. When the strain was grown anaerobically on toluene, 68% of the carbon from toluene was found as CO 2 and 30% was found as biomass. Strain Tol-4 had a doubling time of 4.3 h, a V max of 50 mol ⅐ min ؊1 ⅐ g of protein ؊1 , and a cellular yield of 49.6 g ⅐ mol of toluene ؊1. Benzoate appeared to be an intermediate, since F-benzoates accumulated from F-toluenes and [ 14 C]benzoate was produced from [ 14 C]toluene in the presence of excess benzoate. Two metabolites, E-phenylitaconic acid (1 to 2%) and benzylsuccinic acid (<1%), accumulated from anaerobic toluene metabolism. These same products were also produced when cells were grown on hydrocinnamic acid and trans-cinnamic acid but were not produced from benzylalcohol, benzaldehyde, benzoate, p-cresol, or their hydroxylated analogs. The evidence supports an anaerobic toluene degradation pathway involving an initial acetyl coenzyme A (acetyl-CoA) attack in strain Tol-4, as proposed by Evans and coworkers (

A strictly anaerobic betaproteobacteriumGeorgfuchsia toluolicagen. nov., sp. nov. degrades aromatic compounds with Fe(III), Mn(IV) or nitrate as an electron acceptor

“…According to this approach, the biomass (C 5 H 7 O 2 N) yield is 43 g biomass per mole toluene, which is in fairly good agreement with the measured yield (30 g biomass per mole toluene). For A. tolulyticus strain Tol-4, a biomass yield of 49.6 g biomass per mol toluene has been reported (Chee-Sanford et al, 1996).…”

Anaerobic Metabolism of Aromatic Compounds

“…The pathway of benzylsuccinate oxidation to benzoyl-CoA has not yet been elucidated. Whole cell suspensions of different toluene-grown denitrifying and sulfate-reducing strains are known to convert varying amounts of toluene to benzylsuccinate and derivatives thereof (Evans et al, 1992;Beller et al, 1992;Seyfried et al, 1994;Rabus and Widdel, 1995a;Chee-Sanford et al, 1996;Migaud et al, 1996). This intermediate accumulation in the medium may be best ascribed to variable amounts of cell lysis in the experiments, since none of the toluene-degrading strains so far studied can degrade exogenous benzylsuccinate.…”

Analysis of bacterial and protozoan communities in an aquifer contaminated with monoaromatic hydrocarbons

“…However, these techniques only allow a low percentage of the total number of microorganisms to be assessed [2]. Many recent studies have focused on the isolation and characterization of bacteria capable of degrading speci¢c contaminants [12,33,48], on determining their catabolic pathways [7,47], or on determining the catabolic potential of natural populations in laboratory aquifer columns [21,22]. Consequently, the impact of natural communities of bacteria on the degradation of contaminants in the ¢eld remains poorly understood.…”

“…Total number of bacteria determined after DAPI staining (b) and the percentage of cells detectable after hybridization with the Cy3-labeled probe Eub338(7) in cores A, B, and C at depths between 0.1 m and 7.0 m.…”

“…Total number of protozoa as determined by in situ hybridization with the Eukarya-speci¢c probe Euk516 (b) and by the MPN technique(7) in cores A, B, and C at depths between 0.1 m and 7.0 m.…”