Degradation of chlorothalonil via thiolation and nitrile hydration by marine strains isolated from the surface seawater of the Northwestern Pacific

Chlorothalonil, a commonly used chlorinated benzonitrile fungicide, is often detected in various environments, including marine ecosystems, and poses a threat to human health and environmental safety. Although the biodegradation of chlorothalonil via several catabolic pathways has been reported by various kinds of microorganisms, the degradation of chlorothalonil by marine strains, as well as their special catabolic pathways, remain to be studied. In this study, six strains of chlorothalonil-degrading bacteria (Sulfitobacter sp. S-1, Sphingobium sp. P-1, Marinicauda sp. M-1, Erythrobacter sp. E-17, Stakelama sp. P-2 and Oceanicaulis sp. B-1) were screened and characterized from a total of 110 culturable bacterial strains obtained from the surface seawater of the Northwestern Pacific. Sphingobium sp. P-1, showing the highest degrading efficiency among the six degraders, and was thus selected for further investigation. Strain P-1 completely removed 20 mg L−1 of chlorothalonil from mineral salt-carbon medium within 24 h and from seawater within 3 d. During the degradation of chlorothalonil by strain P-1, two metabolites (4-sulfydryl-2,5,6-trichloroisophthalonitrile and 5-cyano-4,6,7-trichloro-2H-1,2-benzisothiazol-3-one) were detected and identified by liquid chromatography–mass spectrometry that suggest a special catabolic pathway of chlorothalonil via thiolation and nitrile hydration in the marine strain P-1. •Diverse bacterial strains were isolated from the surface seawater of the Northwestern Pacific.•Six marine bacteria were capable of degrading chlorothalonil.•Sphingobium sp. P-1 had excellent degrading capacities for chlorothalonil in both MCM medium and seawater.•A new catabolic pathway of chlorothalonil via thiolation and nitrile hydration was proposed in strain P-1.