Reversible Conversion of 4-Hydroxybenzoate and Phenol by Clostridium hydroxybenzoicum.

Reversible conversion of 4-hydroxybenzoate and phenol and their analogs was observed in whole-cell suspensions and cell extracts of Clostridium hydroxybenzoicum grown with 4-hydroxybenzoate and 3,4-dihydroxybenzoate. Assuming that bicarbonate is the cosubstrate, the equilibrium constants calculated for the reactions 4-hydroxybenzoate + H(2)O left arrow over right arrow phenol + HCO(3) and 3,4-dihydroxybenzoate + H(2)O left arrow over right arrow catechol + HCO(3) were 11.4 (+/- 0.5) and 5.05 (+/- 0.25), respectively. In a phenol-adapted sediment slurry, 4-hydroxybenzoate and 3,4-dihydroxybenzoate were decarboxylated to phenol and to catechol, respectively, as intermediates without a lag time.