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Cyhalothrin is a kind of effective, broad-spectrum and quick acting pyrethroid insecticide and acaricide, which is mainly contact killing and stomach toxicity, and has no inhaling effect. It mainly inhibits the conduction of the nerve axons of insects, and has the functions of avoiding, knocking down and poisoning insects. It has a wide range of insecticidal spectrum and rapid efficacy. It has a certain control effect on the pests and mites of the piercing suction mouthparts, and has a long period of efficacy. It is a typical pesticide insecticide. With the ban of organochlorine, organophosphorus and other highly toxic pesticides, cyhalothrin has been widely used in agricultural production, pest control and public health due to its high biological activity and spectral type. Therefore, safety problems also follow.
Wang Ruoyu, Cao Ming and Chen Jingyu from Agricultural University of China screened safe strains for degradation of Cypermethrin from Daqu, selected the best degradation strains by measuring the degradation of different low-quality concentrations of Cypermethrin, identified them with molecular biology technology, analyzed the correlation between their growth and the degradation dynamics of Cypermethrin, and used simulation mixing The degradation ability of agricultural residues was verified by the system of integrated agricultural residues. The results showed that Rhodococcus rhodochrosis L5 had the best degradation effect on Cypermethrin with a mass concentration of 5 mg / L, and the degradation rate was 71.44%. The degradation effect was related to its growth density, and it could effectively degrade simulated mixed agricultural residues. It was a promising pesticide degradation bacteria.
Screening results of Cypermethrin Degrading Bacteria
Strains L1, L5, L11, L15, L22 can tolerate cypermethrin and continue to grow. The growth ability of these five strains was further determined.
The growth of strains L1 and L5 is relatively vigorous. They quickly break through the lag period in LB medium and enter the logarithmic growth period, and the growth situation is significantly better than strains L11, L15 and L22. Therefore, strains L1 and L5 are selected as the target strains.
Identification of Cypermethrin Degrading Bacteria
Strains L1 and L5 were closely related to the two strains, respectively. Therefore, it was determined that strain L1 was leucobacter komagatae and strain L5 was Rhodococcus rhodochlous.
Determination of degradation rate of Cyhalothrin
Strains L1 and L5 had certain degradation ability to cypermethrin with mass concentration of 2 mg / L, 5 mg / L and 10 mg / L. When the mass concentration of Cypermethrin was 5 mg / L, the degradation rate was the highest, and the degradation rate of strain L5 reached 71.44%, indicating that the mass concentration of 5 mg / l was close to the optimal growth quality concentration of the strain. At the same time, it was found that strain L5 had better degradation effect, Rhodococcus roseus had the characteristics of metabolic diversity, and could effectively remove a variety of compounds, such as oil pollution remediation, degradation of organic pesticides and so on. In addition, Rhodococcus can also be used as probiotics of some aquaculture animals, which can provide the necessary carotenoids for aquaculture animals. It is a safe strain with application prospect. Therefore, the degradation characteristics of Cypermethrin of strain L5 were further analyzed.
Correlation between the growth of strain L5 and the degradation of Cypermethrin
In the control group of L5, the mass concentration of Cypermethrin decreased from 4.95 mg / L to 3.98 mg / L, while that of L5 decreased from 4.94 mg / L to 1.13 mg / L, which showed that L5 had a strong ability to degrade cypermethrin. Adding 5 mg / L of Cypermethrin to MSM, the OD600 nm value of strain L5 was higher than that of MSM without Cypermethrin, which indicated that the addition of Cypermethrin could promote the growth of strain L5. The results showed that the concentration of Cypermethrin was related to the growth density of the strain.
Effects of mixed pesticides on the growth and degradation rate of L5
Compared with the growth of strain L5 in MSM without pesticide addition, the growth of strain L5 in MSM with mixed pesticide was obviously promoted. At the same time, all seven pesticides were degraded. Maybe because strain L5 has high tolerance to mixed pesticide, it can use mixed pesticide as carbon source to grow or co metabolize pesticide with glucose as primary energy It promoted the growth of L5, accelerated the degradation rate of mixed pesticides under natural conditions and improved the degradation rate of mixed pesticides. Among MSM containing mixed pesticides, strain L5 has an absolute advantage in degrading cyhalothrin, Fenvalerate and deltamethrin by 52.8%, 44.6% and 37.5%, respectively. Meanwhile, strain L5 has a higher degradation rate and a wider degradation spectrum for imidacloprid, endosulfan, metalaxyl and other pesticide types.
conclusion
In this study, five strains were isolated from Daqu, which could degrade cypermethrin efficiently. Strains L1 and L5 grew vigorously and the degradation rate of Cypermethrin was high. They were identified as leucobacter komagatae and Rhodococcus rhodochlous respectively by molecular biological technology. The two strains had the best degradation effect on 5 mg / L Cypermethrin, and the degradation rate of Rhodococcus roseus L5 was the highest, reaching 71.44%. The addition of Cypermethrin can promote the growth of Rhodococcus roseus L5, and the growth of Rhodococcus roseus L5 can promote the degradation of cypermethrin. The concentration change of Cypermethrin is related to the growth density of the strain. In the mixed agricultural residue system, Rhodococcus roseus L5 has strong degradation ability, among which, the degradation rate of Cypermethrin is the highest, the degradation rate reaches 52.8%. The degradation rate of fenvalerate, deltamethrin, imidacloprid, endosulfan, metalaxyl and other insecticides is higher, more than 20%, with a wide degradation spectrum. In conclusion, Rhodococcus roseus L5 is a functional strain with excellent performance, vigorous growth and wide degradation spectrum, which has a potential application prospect in the single or mixed pesticide residue system of high-efficiency cypermethrin.
In this paper, the isolation, screening and characterization of Cypermethrin Degrading Bacteria in Daqu is from China Brewing, Vol. 39, No. 3, page 21-25, 2020. The authors are Wang Ruoyu, Cao Ming and Chen Jingyu.
doi: 10.11882/j.issn.0254-5071.2020.03.005。
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