Metabolic pathway for degradation of anthracene by halophilic Martelella sp. AD-3

Anthracene (40mgl^-1) was completely depleted by Martelella sp. strain AD-3 under 3% salinity and a pH of 9.0 after 6 days of incubation. The metabolites were extracted and identified by high-performance liquid chromatography (HPLC) retention times, mass spectrometry, ¹H and ¹³C nuclear magnetic resonance spectrometry, and comparison to authentic compounds or literature data. On the basis of the identified metabolites, enzyme activities and the utilization of probable intermediates, anthracene degradation by strain AD-3 is proposed via two distinct routes. In route I, metabolism of anthracene is initiated by the dioxygenation at C-1,2, then proceeds through 6,7-benzocoumarin, 3-hydroxy-2-naphthoic acid, salicylic acid and gentisic acid. In route II, anthracene is metabolized to 9,10-anthraquinone. The results suggest that strain AD-3 possesses efficient anthracene biodegradability in high salinity. To our knowledge, this work presents the first report of anthracene degradation by a halophilic PAH-degrading strain via two routes. The strain AD-3 may be a useful candidate for PAH-contaminated saline-alkali soil bioremediation.