The pathways by which the marine diatom Thalassiosira sp. OUC2 biodegrades p-xylene, combined with a mechanistic analysis at the proteomic level

A marine diatom, Thalassiosira sp. OUC2, was isolated from natural seawater collected from Daya Bay, China. This diatom degraded 1.25-40 mg L-1 p-xylene within five days, at a removal efficiency exceeding 98%. Gas chromatography-mass spectrometer (GC-MS) analysis indicated that p-xylene was converted into 4-methylbenzyl alcohol, p-toluic acid, and p-cresol in the presence of strain OUC2. Meanwhile, proteomic analysis showed that, after exposure to p-xylene, several algal enzymes were significantly upregulated: including monooxygenase, alcohol dehydrogenase, benzaldehyde dehydrogenase, benzoate 1,2-dioxygenase, and catechol 2,3-dioxygenase. Moreover, ecotoxicological tests suggested that the intermediate metabolites were less toxic than the parent compound (p-xylene). Thalassiosira sp. OUC2 may thus be suitable for the remediation of p-xylene-contaminated marine environments.