Abstract
In this study, we isolated an endophytic quinclorac-degrading bacterium strain Q3 from the root of tobacco grown in quinclorac contaminated soil. Based on morphological characteristics, Biolog identification, and 16S rDNA sequence analysis, we identified strain Q3 as Bacillus megaterium. We investigated the effects of temperature, pH, inoculation size, and initial quinclorac concentration on growth and degrading efficiency of Q3. Under the optimal degrading condition, Q3 could degrade 93% of quinclorac from the initial concentration of 20 mg/L in seven days. We analyzed the degradation products of quinclorac using liquid chromatography–tandem mass spectrometry (LC-MS/MS). The major degradation products by Q3 were different from those of previously identified quinclorac degrading strains, which suggests that Q3 may employ new pathways for quinclorac degradation. Our indoor pot experiments demonstrated that Q3 can effectively alleviate the quinclorac phytotoxicity in tobacco. As the first endophytic microbial that is capable of degrading quinclorac, Q3 can be a good bioremediation bacterium for quinclorac phytotoxicity.
Highlights
Quinclorac (3,7-dichloro-8-quinoline-carboxylic) is a highly selective auxin herbicide developed by the BASF Corporation
Quinclorac stimulates the induction of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase, a key enzyme in ethylene formation, which leads to the accumulation of cyanide in the tissues of plants and —to their death [2,3]
We were able to isolate six bacteria strains that colonize with clear zones
Summary
Quinclorac (3,7-dichloro-8-quinoline-carboxylic) is a highly selective auxin herbicide developed by the BASF Corporation. Two major methods are used to reduce quinclorac contamination They are photodegradation and microbial degradation [7,8]. Several quinclorac degrading strains were isolated from quinclorac-contaminated soil. Isolated a WZ1 strain from pesticide manufactory soil, which was capable of degrading quinclorac [10]. WZ1 degraded 90% of quinclorac from an initial concentration of 1000 mg/L in 11 days [10,11,12]. The J3 strain degraded 70% of quinclorac from initial concentration of 100 mg/L in 7 days at optimal conditions [14]. The strain QC06 degraded 95.31% of quinclorac from initial concentration of 50 mg/L in 7 days at optimal degrading conditions [15]
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