Knowledge on the behavior and fate of pharmaceuticals and personal care products (PPCPs) is poorly explored in marine aphotic environment. In this study, the degradation mechanism of a typical PPCPs-ibuprofen (IBP) by a ubiquitous marine Pseudoalteromonas sp. was investigated based on transcriptome and key enzymes analysis. More importantly, a novel enzymatic-nonenzymatic coupling degradation mechanism was uncovered for the first time, namely, the degradation of IBP was firstly initiated by extracellular reactive oxygen species (ROS), then the intermediate (e.g.4-ethylresorcinol) was further degraded by intracellular enzymes. It was showed that biogenic •OH, O2•-and H2O2 were responsible for extracellular nonenzymatic degradation, in which IBP was degraded to 4-ethylresorcinol through hydrogenation, isobutyl moiety cleavage, oxidation and decarboxylation. 4-Hydroxyphenylpyruvate dioxygenase, homogentisate 1,2-dioxygenase, long-chain acyl-CoA synthetase, acetyl-CoA acyltransferase and enoyl-CoA hydratase were identified to be involved in intracellular degradation, leading 4-ethylresorcinol cracked and eventually mineralized. Ultimately, this novel degradation mechanism was demonstrated to be amino acids-driven through KEGG enrichment analysis and experimental data. Overall, our work uncovered a yet undiscovered abiotic-biotic coupling degradation mechanism in PPCPs biotransformation, thereby updating the conventional concept that contaminants transformation is solely accomplished by enzymes or non-enzymes, which can also provide new insights into PPCPs environmental behavior and fate.
Keywords: Degradation pathway; Marine environment; Novel degradation mechanism; PPCPs; Transcriptome.
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