Elucidation of 4-Hydroxybenzoic Acid Catabolic Pathways in Sphe3.

4-hydroxybenzoic acid (4-HBA) is an aromatic compound with high chemical stability, being extensively used in food, pharmaceutical and cosmetic industries and therefore widely distributed in various environments. Bioremediation constitutes the most sustainable approach for the removal of 4-hydroxybenzoate and its derivatives (parabens) from polluted environments. Sphe3, a strain capable of degrading several aromatic compounds, is able to grow on 4-HBA as the sole carbon and energy source. Here, an attempt is made to clarify the catabolic pathways that are involved in the biodegradation of 4-hydroxybenzoate by Sphe3, applying a metabolomic and transcriptomic analysis of cells grown on 4-HBA. It seems that in Sphe3, 4-hydroxybenzoate is hydroxylated to form protocatechuate, which subsequently is either cleaved in - and/or -positions or decarboxylated to form catechol. Protocatechuate and catechol are funneled into the TCA cycle following either the -ketoadipate or protocatechuate -cleavage branches. Our results also suggest the involvement of the oxidative decarboxylation of the protocatechuate peripheral pathway to form hydroxyquinol. As a conclusion, Sphe3 seems to be a rather versatile strain considering the 4-hydroxybenzoate biodegradation, as it has the advantage to carry it out effectively following different catabolic pathways concurrently.