Guangdong Laboratory for Lingnan Modern Agriculture, Integrative Microbiology Research Centre, College of Plant Protection, South China Agricultural University, Guangzhou, 510642, China.
Guangdong Laboratory for Lingnan Modern Agriculture, Integrative Microbiology Research Centre, College of Plant Protection, South China Agricultural University, Guangzhou, 510642, China; Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, 650500, China.
Environ Res. 2023 Nov 1;236(Pt 1):116619. doi: 10.1016/j.envres.2023.116619. Epub 2023 Jul 21.
Beta-cypermethrin is one of the widely used pyrethroid insecticides, and problems associated with the accumulation of its residues have aroused public attention. Thus, there is an urgent need to effectively remove the beta-cypermethrin that is present in the environment. Biodegradation is considered a cost-effective and environmentally friendly method for removing pesticide residues. However, the beta-cypermethrin-degrading microbes that are currently available are not optimal. In this study, Pseudomonas aeruginosa PAO1 was capable of efficiently degrading beta-cypermethrin and its major metabolite 3-phenoxybenzaldehyde in water/soil environments. Strain PAO1 could remove 91.4% of beta-cypermethrin (50 mg/L) in mineral salt medium within 120 h. At the same time, it also possesses a significant ability to metabolize 3-phenoxybenzaldehyde-a toxic intermediate of beta-cypermethrin. The Andrews equation showed that the maximum substrate utilization concentrations of beta-cypermethrin and 3-phenoxybenzaldehyde by PAO1 were 65.3558 and 49.6808 mg/L, respectively. Box-Behnken design-based response surface methodology revealed optimum conditions for the PAO1 strain-based degradation of beta-cypermethrin as temperature 30.6 °C, pH 7.7, and 0.2 g/L inoculum size. The results of soil remediation experiments showed that indigenous micro-organisms helped to promote the biodegradation of beta-cypermethrin in soil, and beta-cypermethrin half-life in non-sterilized soil was 6.84 days. The bacterium transformed beta-cypermethrin to produce five possible metabolites, including 3-phenoxybenzyl alcohol, methyl 2-(4-hydroxyphenoxy)benzoate, diisobutyl phthalate, 3,5-dimethoxyphenol, and 2,2-dimethyl-1-(4-phenoxyphenyl)propanone. Among them, methyl 2-(4-hydroxyphenoxy)benzoate and 3,5-dimethoxyphenol were first identified as the intermediate products during the beta-cypermethrin degradation. In addition, we propose a degradation pathway for beta-cypermethrin that is metabolized by strain PAO1. Beta-cypermethrin could be biotransformed firstly by hydrolysis of its carboxylester linkage, followed by cleavage of the diaryl bond and subsequent metabolism. Based on the above results, P. aeruginosa PAO1 could be a potent candidate for the beta-cypermethrin-contaminated environmental bioremediation.
β-氯氰菊酯是一种广泛使用的拟除虫菊酯类杀虫剂，其残留积累所带来的问题引起了公众的关注。因此，迫切需要有效地去除环境中的β-氯氰菊酯。生物降解被认为是去除农药残留的一种具有成本效益和环保的方法。然而，目前可用的β-氯氰菊酯降解微生物并不理想。在这项研究中，铜绿假单胞菌 PAO1 能够在水/土壤环境中有效降解β-氯氰菊酯及其主要代谢物 3-苯氧基苯甲醛。PAO1 菌株在无机盐培养基中 120 小时内可去除 50mg/L 的β-氯氰菊酯（91.4%）。同时，它还具有显著的代谢 3-苯氧基苯甲醛的能力，3-苯氧基苯甲醛是β-氯氰菊酯的一种有毒中间产物。Andrews 方程表明，PAO1 对β-氯氰菊酯和 3-苯氧基苯甲醛的最大底物利用浓度分别为 65.3558 和 49.6808mg/L。基于 Box-Behnken 设计的响应面法揭示了 PAO1 菌株降解β-氯氰菊酯的最佳条件为温度 30.6°C、pH7.7 和 0.2g/L 接种量。土壤修复实验结果表明，土著微生物有助于促进土壤中β-氯氰菊酯的生物降解，未灭菌土壤中β-氯氰菊酯的半衰期为 6.84 天。该细菌将β-氯氰菊酯转化为 5 种可能的代谢物，包括 3-苯氧基苯甲醇、甲基 2-(4-羟基苯氧基)苯甲酸酯、邻苯二甲酸二异丁酯、3,5-二甲氧基苯酚和 2,2-二甲基-1-(4-苯氧基苯基)丙酮。其中，甲基 2-(4-羟基苯氧基)苯甲酸酯和 3,5-二甲氧基苯酚首次被鉴定为β-氯氰菊酯降解过程中的中间产物。此外，我们提出了 PAO1 菌株代谢β-氯氰菊酯的降解途径。β-氯氰菊酯首先通过其羧酯键的水解进行生物转化，然后裂解二芳基键并进行后续代谢。基于上述结果，铜绿假单胞菌 PAO1 可能是一种很有前途的β-氯氰菊酯污染环境生物修复候选菌株。
