Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou 510642, China.
Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou 510642, China.
Int J Mol Sci. 2021 Aug 26;22(17):9242. doi: 10.3390/ijms22179242.
Tetramethrin is a pyrethroid insecticide that is commonly used worldwide. The toxicity of this insecticide into the living system is an important concern. In this study, a novel tetramethrin-degrading bacterial strain named A16 was isolated from the activated sludge and identified as . Strain A16 exhibited superior tetramethrin degradation activity, and utilized tetramethrin as the sole carbon source for growth in a mineral salt medium (MSM). High-performance liquid chromatography (HPLC) analysis revealed that the A16 strain was able to completely degrade 25 mg·L of tetramethrin after 9 days of incubation. Strain A16 effectively degraded tetramethrin at temperature 20-40 °C, pH 5-9, and initial tetramethrin 25-800 mg·L. The maximum specific degradation rate (), half-saturation constant (), and inhibition constant () were determined to be 0.4561 day, 7.3 mg·L, and 75.2 mg·L, respectively. The Box-Behnken design was used to optimize degradation conditions, and maximum degradation was observed at pH 8.5 and a temperature of 38 °C. Five intermediate metabolites were identified after analyzing the degradation products through gas chromatography-mass spectrometry (GC-MS), which suggested that tetramethrin could be degraded first by cleavage of its carboxylester bond, followed by degradation of the five-carbon ring and its subsequent metabolism. This is the first report of a metabolic pathway of tetramethrin in a microorganism. Furthermore, bioaugmentation of tetramethrin-contaminated soils (50 mg·kg) with strain A16 (1.0 × 10 cells g of soil) significantly accelerated the degradation rate of tetramethrin, and 74.1% and 82.9% of tetramethrin was removed from sterile and non-sterile soils within 11 days, respectively. The strain A16 was also capable of efficiently degrading a broad spectrum of synthetic pyrethroids including D-cyphenothrin, chlorempenthrin, prallethrin, and allethrin, with a degradation efficiency of 68.3%, 60.7%, 91.6%, and 94.7%, respectively, after being cultured under the same conditions for 11 days. The results of the present study confirmed the bioremediation potential of strain A16 from a contaminated environment.
四氯苯菊酯是一种拟除虫菊酯类杀虫剂，在全世界广泛使用。这种杀虫剂进入生命系统的毒性是一个重要的关注点。在这项研究中，从活性污泥中分离到一株新型的四氯苯菊酯降解细菌菌株 A16，并鉴定为 。菌株 A16 表现出优异的四氯苯菊酯降解活性，并且能够在无机盐培养基（MSM）中利用四氯苯菊酯作为唯一的碳源进行生长。高效液相色谱（HPLC）分析表明，A16 菌株在 9 天的孵育后能够完全降解 25mg·L 的四氯苯菊酯。菌株 A16 在 20-40°C、pH5-9 和初始四氯苯菊酯 25-800mg·L 的条件下有效地降解四氯苯菊酯。最大比降解速率（）、半饱和常数（）和抑制常数（）分别确定为 0.4561 天、7.3mg·L 和 75.2mg·L。通过 Box-Behnken 设计优化降解条件，在 pH8.5 和 38°C 时观察到最大降解。通过气相色谱-质谱联用（GC-MS）分析降解产物，鉴定出 5 种中间代谢产物，表明四氯苯菊酯首先可以通过其羧基酯键的断裂进行降解，然后降解五环及其随后的代谢。这是在微生物中报道的四氯苯菊酯代谢途径的首次报道。此外，用菌株 A16（1.0×10 个细胞 g 的土壤）对含有 50mg·kg 的四氯苯菊酯污染土壤进行生物强化显著加速了四氯苯菊酯的降解速率，在 11 天内，无菌和非无菌土壤中分别去除了 74.1%和 82.9%的四氯苯菊酯。菌株 A16 在相同条件下培养 11 天后，还能够有效地降解 D-氯氰菊酯、氯氟醚菊酯、炔丙菊酯和丙烯菊酯等多种合成拟除虫菊酯，降解效率分别为 68.3%、60.7%、91.6%和 94.7%。本研究的结果证实了 A16 菌株从污染环境中的生物修复潜力。
