Duc Ha Danh
Dong Thap University, 783 Pham Huu Lau Street, Cao Lanh City, Dong Thap Province, 81100, Viet Nam.
FEMS Microbiol Lett. 2023 Jan 17;370. doi: 10.1093/femsle/fnac123.
Thiobencarb is a highly effective thiocarbamate herbicide frequently used in rice fields globally. In this study, three bacterial strains (Dechloromonas sp. Th1, Thauera sp. Th2, and Azoarcus sp. Th3) isolated from immobilized biomass were analyzed for thiobencarb degradation under anaerobic conditions, with nitrate serving as an electron acceptor. The experimental results showed that thiobencarb was transformed by Dechloromonas sp. Th1 and Thauera sp. Th2 to produce high concentrations of metabolites in a mineral medium. Dechloromonas sp. Th1 dechlorinated the herbicide to benzyl mercaptan, which was then degraded by Thauera sp. Th2 and Azoarcus sp. Th3. Azoarcus sp. Th3 effectively degraded intermediates, i.e. 4-chlorobenzyl alcohol, 4-chlorobenzoic acid, and benzoic acid, produced from the degradation by Dechloromonas sp. Th1 and Thauera sp. Th2. The cross-feeding, nutrient sharing, and cooperation of all isolates in the degradation process decreased the concentrations of intermediate products. The determination of the degradation kinetics showed that the utilization in the exponential phase of the mixed bacteria was consistent with the Michaelis-Menten model, with a maximum degradation rate of 1.56 ± 0.16 µM day-1. This study showed the degradation mechanisms in bacteria and the synergistic process in the degradation of thiobencarb and its metabolites.
杀草丹是一种高效的硫代氨基甲酸酯类除草剂，在全球稻田中广泛使用。在本研究中，分析了从固定化生物质中分离出的三株细菌（脱氯单胞菌属Th1、陶厄氏菌属Th2和偶氮弧菌属Th3）在厌氧条件下以硝酸盐作为电子受体对杀草丹的降解情况。实验结果表明，脱氯单胞菌属Th1和陶厄氏菌属Th2在矿物培养基中转化杀草丹产生高浓度的代谢产物。脱氯单胞菌属Th1将除草剂脱氯生成苄硫醇，然后苄硫醇被陶厄氏菌属Th2和偶氮弧菌属Th3降解。偶氮弧菌属Th3有效降解了由脱氯单胞菌属Th1和陶厄氏菌属Th2降解产生的中间体，即4-氯苄醇、4-氯苯甲酸和苯甲酸。所有分离菌株在降解过程中的交叉喂养、营养共享和合作降低了中间产物的浓度。降解动力学测定表明，混合菌指数期的利用情况符合米氏模型，最大降解速率为1.56±0.16 μM·天-1。本研究揭示了细菌中的降解机制以及杀草丹及其代谢产物降解过程中的协同作用。
