Department of Chemical Engineering, Tsinghua University, Beijing, 100084, PR China.
School of Petrochemical Engineering, Liaoning Shihua University, Fushun, 113001, PR China.
Chemosphere. 2018 May;199:210-217. doi: 10.1016/j.chemosphere.2018.01.133. Epub 2018 Feb 3.
Quinclorac, a highly selective auxin herbicide, is widely used for controlling weeds in rice field. However, the residual quinclorac is toxic to many crops, vegetables, and aquatic animals, resulting in one of the major problems in crop rotation. Here, we investigated the degradation of quinclorac by strain AH-B, which was isolated from long-term quinclorac-contaminated soil using continuous circulating fluidized bed reactor and subjected to atmospheric and room temperature plasma mutation. Morphological examination, 16S rRNA gene sequencing, and phylogenetic analysis revealed that strain AH-B was Streptomyces sp. The quinclorac degradation efficiency of AH-B in liquid medium was 97.2% after 18 days when the initial quinclorac concentration was 20 mg L. The degradation products were 3-chloro-7-methoxy-8-quinoline-carboxylic, 3-chloro-7-methyl-8-quinoline-carboxylic, 3-chloro-7-oxyethyl-8-quinoline-carboxylic, and 3,7-dichloro-6-methyl-8-quinoline-carboxylic. The inoculum size, initial quinclorac concentration, pH, and temperature were found to affect quinclorac degradation efficiency of AH-B. High-performance liquid chromatography-electrospray ionization tandem mass spectrometry analysis revealed that quinclorac degradation by AH-B produced many products. In soil with initial quinclorac content of 1 mg kg dry soil, addition of AH-B resulted in 87.5% quinclorac degradation after 42 days, while that in the control (without AH-B) was 22.4%. Furthermore, microecological analysis using next-generation sequencing of 16S rRNA geneshowed that some bacterial species, such as Bacterioides and Proteobacteria, could survive in quinclorac-contaminated soil, while some bacteria, such as Firmicutes, were very sensitive to quinclorac. Besides, some fungal species, such as Basidiomycota, could also survive quinclorac-contamination. After 42 days, the diversity of bacteria and fungi in soil treated with AH-B was higher than that in the control, implying that bioaugmentation with strain AH-B could reduce quinclorac toxicity to microorganisms in soil.
精喹禾灵是一种高度选择性的生长素除草剂，广泛用于稻田杂草控制。然而，残留的精喹禾灵对许多作物、蔬菜和水生动物有毒，这是轮作中的主要问题之一。在这里，我们研究了从长期受精喹禾灵污染的土壤中分离出的菌株 AH-B 对精喹禾灵的降解。该菌株在常压和室温等离子体突变体下使用连续循环流化床反应器进行处理。形态学检查、16S rRNA 基因测序和系统发育分析表明，菌株 AH-B 是链霉菌属。当初始精喹禾灵浓度为 20mg/L 时，AH-B 在液体培养基中 18 天后对精喹禾灵的降解效率为 97.2%。降解产物为 3-氯-7-甲氧基-8-喹啉羧酸、3-氯-7-甲基-8-喹啉羧酸、3-氯-7-乙氧基-8-喹啉羧酸和 3,7-二氯-6-甲基-8-喹啉羧酸。接种量、初始精喹禾灵浓度、pH 值和温度均影响 AH-B 对精喹禾灵的降解效率。高效液相色谱-电喷雾串联质谱分析表明，AH-B 降解精喹禾灵产生了许多产物。在初始精喹禾灵含量为 1mg/kg 干土的土壤中，添加 AH-B 42 天后可使精喹禾灵降解 87.5%，而对照（不添加 AH-B）为 22.4%。此外，使用 16S rRNA 基因的下一代测序进行的微生态分析表明，一些细菌物种，如拟杆菌和变形菌，能够在精喹禾灵污染的土壤中存活，而一些细菌，如厚壁菌门，对精喹禾灵非常敏感。此外，一些真菌物种，如担子菌门，也能在精喹禾灵污染的土壤中存活。42 天后，添加 AH-B 处理的土壤中细菌和真菌的多样性高于对照，这意味着用菌株 AH-B 进行生物增强可以降低精喹禾灵对土壤中微生物的毒性。
