Catabolism of 4-Hydroxybenzoic Acid by Pseudomonas sp. DJ-12

A Pseudomonas sp. strain DJ-12 isolated by 4-chlorobiphenyl enrichment culture technique is capable of utilizing 4-hydroxybenzoic acid as a sole source of carbon and energy. The bacterium catabolized 4-hydroxybenzoic acid through the intermediate formation of protocatechuic acid, which was further metabolized. The cell free extracts of Pseudomonas sp. DJ-12, grown on 4-hydroxybenzoic acid showed higher activities of 4-hydroxybenzoate 3-hydroxylase and protocatechuate 4,5-dioxygenase, but the activity of catechol 2,3-dioxygenase was lower. The results suggest that 4-hydroxybenzoic acid is catabolized via protocatechuic acid rather than catechol or gentisic acid in this bacterium and that the protocatechuic acid formed was metabolized through a metacleavage pathway by protocatechuate 4,5-dioxygenase.