Limited Roles for Salicylate and Phthalate in Bacterial PAH Bioremediation

We have isolated and identified 12 previously unreported strains of polycyclic aromatic hydrocarbon (PAH)-degrading bacteria. Three of these isolates belong to the genus Burkholderia, with the remainder comprised of two Pseudomonas species, and seven strains from the genus Sphingomonas. These isolates were examined for their ability to utilize a variety of three- to five-ring PAHs as sole sources of carbon and energy. All were also checked for the ability to grow on salicylic acid and phthalic acid, two compounds that are key intermediates in almost all published PAH degradative pathways. Only 3 of the 12 strains were able to grow on both of these monoaromatic acids, while three others (all Sphingomonas) could not grow on either. The implications of these findings on the universal applicability of known PAH catabolic pathways, and on possible induction of PAH degradation by pathway intermediates, are discussed.