Use of stable isotopes to identify benzoate as a metabolite of benzene degradation in a sulphidogenic consortium

An enriched sulphidogenic consortium capable of mineralizing benzene was used to study the metabolic pathway of anaerobic benzene degradation. Benzoate was detected in active cultures and benzene was confirmed to be the source of this benzoate by the addition of deuterated benzene (D6) and subsequent detection of deuterated benzoate (D5) in active cultures but not in autoclaved controls. Benzoate was utilized by this culture at 1/12 the rate of benzene, while its presence did not inhibit benzene utilization. The benzene utilization rate was reduced, however, in the presence of 2-fluorobenzoate. When the culture was supplemented with [C-13]-bicarbonate, the carboxyl group on benzoate was not labelled with [C-13]-carbon, suggesting that this transformation relies on a more complex set of reactions than simple addition of carbonate.