Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Science, Nanjing Normal University, Nanjing, 210023, People's Republic of China.
The Key Laboratory of Biotechnology for Medicinal Plants of Jiangsu Province and School of Life Science, Jiangsu Normal University, Xuzhou, 221116, People's Republic of China.
Microb Cell Fact. 2021 Jul 13;20(1):133. doi: 10.1186/s12934-021-01620-4.
Flonicamid (N-cyanomethyl-4-trifluoromethylnicotinamide, FLO) is a new type of pyridinamide insecticide that regulates insect growth. Because of its wide application in agricultural production and high solubility in water, it poses potential risks to aquatic environments and food chain.
In the present study, Ensifer adhaerens CGMCC 6315 was shown to efficiently transform FLO into N-(4-trifluoromethylnicotinoyl) glycinamide (TFNG-AM) via a hydration pathway mediated by two nitrile hydratases, PnhA and CnhA. In pure culture, resting cells of E. adhaerens CGMCC 6315 degraded 92% of 0.87 mmol/L FLO within 24 h at 30 °C (half-life 7.4 h). Both free and immobilized (by gel beads, using calcium alginate as a carrier) E. adhaerens CGMCC 6315 cells effectively degraded FLO in surface water. PnhA has, to our knowledge, the highest reported degradation activity toward FLO, V = 88.7 U/mg (K = 2.96 mmol/L). Addition of copper ions could increase the enzyme activity of CnhA toward FLO by 4.2-fold. Structural homology modeling indicated that residue β-Glu56 may be important for the observed significant difference in enzyme activity between PnhA and CnhA.
Application of E. adhaerens may be a good strategy for bioremediation of FLO in surface water. This work furthers our understanding of the enzymatic mechanisms of biodegradation of nitrile-containing insecticides and provides effective transformation strategies for microbial remediation of FLO contamination.
氟啶酰胺(N-氰甲基-4-三氟甲基烟酰胺,FLO)是一种新型吡啶酰胺类昆虫生长调节剂。由于其在农业生产中的广泛应用和在水中的高溶解度,对水生环境和食物链构成了潜在风险。
本研究表明,土壤中分离得到的固氮根瘤菌 Ensifer adhaerens CGMCC 6315 可以通过两种腈水合酶 PnhA 和 CnhA 介导的水合途径将 FLO 高效转化为 N-(4-三氟甲基烟酰基)甘氨酸酰胺(TFNG-AM)。在纯培养条件下,30°C 时,E. adhaerens CGMCC 6315 静止细胞在 24 h 内可降解 0.87 mmol/L 的 FLO 达 92%(半衰期为 7.4 h)。游离细胞和固定化细胞(用凝胶珠,以海藻酸钠为载体)均可有效降解地表水中的 FLO。PnhA 对 FLO 的降解活性最高,V 值为 88.7 U/mg(K 值为 2.96 mmol/L)。添加铜离子可以使 CnhA 对 FLO 的酶活性增加 4.2 倍。结构同源建模表明,残基β-Glu56 可能对 PnhA 和 CnhA 之间观察到的酶活性显著差异很重要。
应用 E. adhaerens 可能是 FLO 地表水污染生物修复的一种良好策略。本研究进一步了解了含腈类杀虫剂生物降解的酶促机制,并为 FLO 污染的微生物修复提供了有效的转化策略。