Metabolism of oxyfluorfen by actinobacteria Micrococcus sp. F3Y

Li Yao¹Yue Wen²Yuting Sha¹Leqin Wang¹Xianrui Bi¹Shuhan Si¹Min Shen¹Shusong Zhang¹Haiyan Ni^3*

• ¹Yancheng Teachers University, Yancheng, Jiangsu, China
• ²Nanjing Tech University, Nanjing, Jiangsu Province, China
• ³Jiangxi Normal University, Nanchang, China

Oxyfluorfen, a potent diphenyl ether herbicide, has raised significant environmental concerns due to its persistence, toxicity to non-target organisms, and potential carcinogenicity. Microbial degradation plays a crucial role in mitigating its impact, yet complete mineralization pathways remain poorly understood. In this study, we isolated and characterized Micrococcus sp. F3Y, an actinobacterial strain that can use oxyfluorfen as its sole carbon source. In yeast powder-supplemented mineral medium (YPM), F3Y showed remarkable degradation efficiency, completely metabolizing 100 mg/L oxyfluorfen within 12 h. Its optimal catalytic activity occurred at pH 7.0, 30°C, and an initial optical density (OD600nm) of 2.0. Notably, F3Y maintained degradation efficiencies above 62% across a pH range of 6.5-8.0 and over 55% within a temperature gradient of 25-42°C, demonstrating its adaptability to environmental changes. When the initial oxyfluorfen concentration was ≤150 mg/L, the degradation rate exceeded 74%. Moreover, in oxyfluorfen-contaminated soil (0.06 mg/kg), inoculation with strain F3Y restored soybean (Glycine max) growth, increasing shoot length from 4.22 cm (severely inhibited) to 28.8 cm, a nearly 7-fold improvement. Additionally, F3Y achieved 98.2% degradation of oxyfluorfen (50 mg/kg) within 25 d in unsterilized soil, demonstrating its high bioremediation potential. Using UPLC/Q-TOF MS, we identified 11 metabolites, including 6 new intermediates. Based on these, two novel degradation pathways were proposed: one initiated by nitro reduction and the other by diaryl ether cleavage. Both pathways culminated in aromatic ring opening and complete mineralization. In addition, a potential 24.3 kb gene cluster, pao, was suggested in the draft genome of strain F3Y. Comprising 13 genes, it was hypothesized to participate in the ring cleavage of intermediate products during oxyfluorfen degradation. This study provided the first comprehensive evidence of Micrococcus mediated oxyfluorfen mineralization, offering new insights into actinobacterial metabolic versatility. With its high degradation efficiency, environmental resilience, and detoxification ability, F3Y was an ideal candidate for bioremediation. Our finding not only enhanced the understanding of herbicide degradation but also provided a sustainable solution to address oxyfluorfen contamination in agricultural and natural ecosystems.