| Chlorantraniliprole is an important insecticide species which has many advantages against the pesticides used currently.For example,it's high toxic to target pests and low toxic to mammals,and it has a long control period.Most importantly,there is no cross-resistance in chlorantraniliprole to the pesticides used currently.Chlorantraniliprole is used as an important alternatives for high toxic pesticides,thus there is an increasing usage amount in recent years.However,there are some potential residue risks of chlorantraniliprole because of its good stability.In our study,we screened a degrading bacteria for chlorantraniliprole based on the contaminated soil.And then,we explored the degradation mechanism of the bacteria.Our study improved the understanding to the environmental behavior of chlorantraniliprole,and it is useful for the scientific and reasonable use of chlorantraniliprole.The results are as follows: 1.An isolate named GW13 with good degradation ability was isolated based on the contaminated soil.GW13 degrades chlorantraniliprole by way of cometabolism.GW13 is short-stem,spore-free and gram-negative.The analysis results of physiological and biochemical showed great similarity with Pseudomonas.And the 16 S rDNA phylogenetic analysis showed the same result.Therefore,we identified the isolate GW13 as Pseudomonas.2.The isolate GW13 grow well in the LB culture medium at 30 ? ~ 35 ?,and 32.5 ? is the best.The pH value of 5 ~ 8 is suitable for GW13 growth,the optimum pH value is 7.And GW13 is aerobic.If NaCl concentrations >3 %,the growth of GW13 is inhibited.Under the optimal growth conditions,isolate GW13 grows in the lag phase in first 2 h,then grows in logarithmic phase after 2 h,then grows in stable phase after 32 h.3.The isolate GW13 degrades chlorantraniliprole by co-metabolism.With the optimal conditions,degradation rate is 70 % to 80 % in 24 h.The optimum conditions are as follow: 0.1 % glucose as the base carbon source,and 200 mg /L chlorantraniliprole as metabolic matrix,0.15 % ammonium nitrate as nitrogen source,28 ? and pH 7.Under the optimal conditions,GW13 grow in lag phase for the first 9 h,then degrades chlorantraniliprole rapidly.After 24 h,the degradation rate is stable and the highest degradation rate is 75.43 %.4.We predicts the degradation pathway of chlorantraniliprole with the help of the EAWAG-BBD database degradation prediction module.The prediction result shows that chlorantraniliprole may be degraded by amide bond cleavage or molecular cyclization.The degradation products were detected by HPLC and UPLC-MS,a small amount of degradation products were detected in the GW13 culture solution.The HPLC spectrum shows that the degradation product has a higher polarity than chlorantraniliprole.And the UPLC-MS spectrum shows that the degradation way of chlorantraniliprole may be molecular dehalogenation.5.The draft genome sequence of isolate GW13 was obtained by Illumina HiSeq sequencing.A total of 128 contigs added up to 5.68 Mbp were obtained.5071 genes with the 969 bp average length were predicted.Among them,4019 genes obtained COG classification and 3184 genes obtained KEGG classification.There were 47 genes in the KEGG xenobiotics biodegradation and metabolism category.There are 105 amidase genes and 5 dehalogenase genes in the genome,and there are many aromatic substances metabolism genes and halide metabolism genes which may be related to the metabolism of chlorantraniliprole.Comparative genomic analysis showed that the isolate GW13 has high homology similarity with the genome of Pseudomonas entomophila L48,with an ANIm value of 89.06 % and an alignment ratio of 73.03 %.GW13 has 402 unique genes relative to Pseudomonas entomophila L48.It contains 223 protein functions,including energy production and conversion,amino acid transport and metabolism,carbohydrate transport and metabolism,coenzyme transport and metabolism,and the discovery of isolates at the genome level.These results improve the understanding for chlorantraniliprole degrading. |
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