Isolation, Identification,Degradation Characteristics And Mechanism Of Cyfluthrin-degrading Strain FLQ-11-1

Synthetic pyrethroids are third generation insecticides, and their residues, which have prompted their widespread use, have generated different degrees of pollutions in soil, air and water, as well as harm to human health. Pesticide residues have become prominent environmental and social problems, which have received increased attention. Bioremediation, which is microbial degradation, is an important way to eliminate pesticide residues and has become a hot research topic in the field of the food and the environmental fields.The FLQ-11-1 strain isolated from a sludge sample obtained from the Fujian Pesticide Chemical Industry Group Co., Ltd, was identified as Lysinibacillus sphaericus using the 16S rDNA sequence, Sherlock MIS and physiology and biochemistry analyse. The degradation characteristics, optimal degradation factors, degradation metabolites, degradation pathway of this strain were also studied, and the degradation of protein expression pattern was investigated using two dimensional electrophoresis (2D) and Gas Chromatography-Mass Spectrometer (GC-MS) identification for clarifying the degradation mechanism. The results were as follows:1. The FLQ-11-1 strain isolated from a sludge sample showed a strong degradation effect on cyfluthrin, and the degradation rate of cyfluthrin (100 mg/L) reached 82% after 72 h at 30℃ and 170 r/min after inoculation with FLQ-11-1. The strain was identified as Lysinibacillus sphaericus using the 16S rDNA sequence, Sherlock MIS and physiology and biochemistry analyses. The strain had 99% homology with Genbank registration number of KC920738. The strain was Gram-positive and rod-shaped.2. Single-factor tests showed that the best degradation performances were with the following single conditions:OD6oonm value of 1.6 (degradation rate of 93.23%, p= 0.032), pH 8.0 (degradation rate of 94.86%, p= 0.019), and 35℃ (degradation rate of 96.1%, p= 0.05). Response surface methodology (RSM) analysis showed that the optimum conditions for degradation were at pH 7 and 35℃, using an inoculum amount with an OD6oonm value of 1.6. The strain FLQ-11-1 also degraded other pyrethroids pesticides. After 5 days of inoculation, the degradation rate of fenpropathrin, fenvalerate, cypermethrin and bifenthrin reached 90.23,83.17,81.63 and 60.83%, respectively, at a pesticide concentration of 100 mg/L.3. Four metabolites were found during the degradation process as follows: methyl3-(2,2-dichlorovinyl)-2,2-dimethyl-(1-cyclopropane) carboxylate, 4-fluoro-3-phenoxy-benzoic acid methyl ester. methyl-3-phenoxybenzoate and 3-phenoxy-benzaldehyde. Three possible metabolic pathways for the cyfluthrin degradation were proposed according the dynamic change of metabolites.4. The protein expression profile for degrading-strain FLQ-11-1 induced by cyfluthrin was analyzed by two-dimensional electrophoresis, and the protein expression profile of the strain without pesticides was used as the control. The results showed that 24 proteins only presented in the sample treatmented with cyfluthin, and 9 proteins and 27 proteins presented triple and double differences in expression level comparing with the control. The PMF identification showed that different proteins belonged to the 27 species. Relevant cyfluthrin-degrading proteins belonged to oxidoreducatases, hydrolases, hydrogenatases, peroxidase. Pathway analysis showed that four metabolite pathways were correlated with the cyfluthrin degradation as follows:phenylalanine metabolism, carbon metabolism, porphyrin and chlorophyll metabolism, and glyoxylate and dicarboxylate metabolism.