Biodegradation of p-hydroxybenzoic acid in soil by Pseudomonas putida CSY-P1 isolated from cucumber rhizosphere soil

Accumulation of p-hydroxybenzonic acid (PHBA) in soil will cause plant stress. Our aims were to characterize PHBA-degrading Pseudomonas putida CSY-P1 and to assess its role on alleviating PHBA stress in plants. Strain CSY-P1 was isolated from rhizosphere soil, and its properties were investigated. The effects of CSY-P1 on soil enzymes and oxidative damage in plants were analyzed. Under PHBA-contaminated environments, antioxidant enzyme activities in CSY-P1 were assessed. Optimal conditions for degradation of PHBA by CSY-P1 were 28 A degrees C, pH 9, and an initial PHBA concentration of 0.6 g l(-1). Protocatechoic acid was a metabolite. CSY-P1 decomposed PHBA effectively in unplanted autoclaved soil. After the strain was applied to PHBA-contaminated cucumber-planted soil, activities of some soil enzymes were increased and the PHBA concentration in soil decreased. Some antioxidant enzyme activities in leaves were elevated, thus reducing malondialdehyde levels in seedlings and mitigating PHBA stress in cucumber. Catalase activity in PHBA-exposed CSY-P1 increased. Pseudomonas putida CSY-P1 degrades PHBA in autoclaved soil and alleviates PHBA stress to plants by inducing some soil enzymes and antioxidant enzymes in leaves. Catalase in strain CSY-P1 contributes to its PHBA tolerance, making it a promising strain for remediation of PHBA-contaminated soil.