State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, 510642, China; Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou, 510642, China.
Wildlife Toxicology Laboratory, Department of Animal Science, Institute for Integrative Toxicology (IIT), Michigan State University, East Lansing, MI, 48824, USA.
Environ Res. 2022 Nov;214(Pt 3):113940. doi: 10.1016/j.envres.2022.113940. Epub 2022 Aug 8.
As a common pyrethroid insecticide, allethrin is widely used for various purposes in agriculture and home applications. At present, allethrin residues have been frequently detected worldwide, yet little is known about the kinetics and degradation mechanisms of this insecticide. In this study, a highly efficient allethrin-degrading bacterium, Bacillus megaterium strain HLJ7, was obtained through enrichment culture technology. Strain HLJ7 can remove 96.5% of 50 mg L allethrin in minimal medium within 11 days. The first-order kinetic analysis of degradation demonstrated that the half-life of allethrin degradation by strain HLJ7 was 3.56 days, which was significantly shorter than the 55.89 days of the control. The Box-Behnken design of the response surface method optimized the degradation conditions for strain HLJ7: temperature 32.18 °C, pH value 7.52, and inoculation amount 1.31 × 10 CFU mL. Using Andrews equation, the optimal concentration of strain HLJ7 to metabolize allethrin was determined to be 21.15 mg L, and the maximum specific degradation rate (q), half-rate constant (K) and inhibition coefficient (K) were calculated to be 1.80 d, 1.85 mg L and 68.13 mg L, respectively. Gas chromatography-mass spectrometry identified five intermediate metabolites, suggesting that allethrin could be degraded firstly by cleavage of its carboxylester bond, followed by degradation of the five-carbon ring and subsequent metabolism. The results of soil remediation experiments showed that strain HLJ7 has excellent bioremediation potential in the soils. After 15 days of treatment, about 70.8% of the initial allethrin (50 mg kg) was removed and converted into nontoxic intermediate metabolites, and its half-life was significantly reduced in the soils. Taken together, these findings shed light on the degradation mechanisms of allethrin and also highlight the promising potentials of B. megaterium HLJ7 in bioremediation of allethrin-comtaminated environment.
作为一种常见的拟除虫菊酯类杀虫剂，丙烯菊酯被广泛应用于农业和家庭用途。目前，丙烯菊酯残留已在全球范围内频繁检出，但对该杀虫剂的动力学和降解机制知之甚少。本研究通过富集培养技术获得了一株高效降解丙烯菊酯的细菌，解淀粉芽孢杆菌 HLJ7 菌株。该菌株在最小培养基中可在 11 天内去除 50mg/L 丙烯菊酯的 96.5%。降解的一级动力学分析表明，HLJ7 菌株降解丙烯菊酯的半衰期为 3.56 天，明显短于对照的 55.89 天。响应面法的 Box-Behnken 设计优化了 HLJ7 菌株的降解条件：温度 32.18°C，pH 值 7.52，接种量 1.31×10CFU/mL。利用 Andrews 方程确定 HLJ7 菌株代谢丙烯菊酯的最佳浓度为 21.15mg/L，最大比降解速率(q)、半速率常数(K)和抑制常数(K)分别为 1.80d、1.85mg/L 和 68.13mg/L。气相色谱-质谱联用仪鉴定了五种中间代谢物，表明丙烯菊酯可先通过其羧基酯键的断裂进行降解，然后降解五环，再进行后续代谢。土壤修复实验结果表明，HLJ7 菌株在土壤中具有良好的生物修复潜力。经过 15 天的处理，初始丙烯菊酯（50mg/kg）约有 70.8%被去除，并转化为无毒的中间代谢物，其半衰期在土壤中明显缩短。综上所述，这些发现揭示了丙烯菊酯的降解机制，也凸显了解淀粉芽孢杆菌 HLJ7 在生物修复丙烯菊酯污染环境中的应用潜力。
