Promotion effect of extracellular abiotic degradation of hexadecane by co-existence of oxalic acid in the culture medium of Pseudomonas aeruginosa NY3

Abstract

Oxalic acid, known as the smallest organic acid produced during biodegradation of persistent organic pollutants (POPs), is ubiquitously existed. But its effect on the biodegradation of POPs was still unclear. This study investigated the promotion mechanism of hexadecane degradation by P. aeruginosa NY3 in the presence of oxalic acid. RT-qPCR and enzyme activity measurements showed that the expression of putative AlkB encoding genes and the activity of AlkB monooxygenase were suppressed when oxalic acid was in the presence of culture medium; meanwhile, degradation ability of hexadecane by cell-free extracellular fluid was greatly promoted. Further study showed that, the promotion mechanism of extracellular degradation of hexadecane by oxalic acid was through its improvement on the secretion of phenazine-1-carboxylic acid (PCA) which reacted with iron ions and oxalic ions to produce hydroxyl radical and resulted in the abiotic degradation of hexadecane in the environment of culture medium. During all the degradation process, the concentration of oxalic acid was nearly unchanged. These results indicated that an abiotic degradation of hexadecane promoted by the coexistence of oxalic acid in the extracellular fluid of P. aeruginosa NY3. • Oxalic acid suppressed expression of the key genes and activity of the corresponding enzyme. • Oxalic acid increased abiotic degradation of hexadecane by extracellular fluid. • Oxalic acid promoted the secretion of PHCs by P. aeruginosa NY3, especially for PCA. • Oxalic acid reacted with metal ions and PHCs to produce hydroxyl radical.