Screening And Soil Remediation Of Nicosulfuron-degrading Bacterium TYM-1

Nicosulfuron is a new type of sulfonylurea herbicide.It is widely used in corn fields due to its high efficiency,low toxicity and good selectivity.It causes a large amount of residue in soil and water,for the natural environment,agricultural production and Human health is extremely harmful.The use of microorganisms to degrade nicosulfuron has the advantages of high efficiency,rapidity,simplicity and convenience,and no secondary pollution.Therefore,it is a hot issue to repair the polluted environment through microbial degradation,and it is of great significance for promoting environmental restoration work.In this study,an enrichment culture method was used to screen and isolate a strain TYM-1 with high-efficiency ability from the surface soil of long-term application of nicosulfuron in Bayan County,Heilongjiang Province.The strain can use nicosulfuron as the sole carbon source or nitrogen source for grown.By high performance liquid chromatography,the degradation rate of degrading bacterium TYM-1 to 100 mg/L of nicosulfuron was 82%within 48 hours,and the degradation effect was better.According to the morphological characteristics of the strain,physiological and biochemical identification results,16 S rDNA sequence analysis results,the strain TYM-1 was identified as Enterobacter sp.,named Enterobacter sp.TYM-1.The growth and degradation characteristics of Enterobacter sp.TYM-1 were studied.It was found that the growth of the strain and the degradation ability of nicosulfuron were better at 48 h.To study the effects of environmental factors on the growth and degradation of strains,it was found that nicosulfuron at a concentration of 100 mg/L is the optimum substrate concentration for growth and degradation of the strain.The optimum temperature is30 ?,and the optimum pH is 8.0.The best carbon source is sucrose.When the nitrogen source is potassium nitrate,the strain has better degradation effect on nicosulfuron.In the microbial soil remediation experiment,the uncontaminated nicosulfuron contaminated soil was selected,and different initial concentrations of strain TYM-1 were inoculated into the soil,cultured at 30 ? for 28 days,and samples were taken every 7 days to detect soil.The residual amount of nicosulfuron-methyl showed that when the initial concentration of the bacteria was 1×10~8 CFU/m L,the degradation rate of the contaminated soil with nicosulfuron concentration of 10 mg/kg was 79%.When the degrading bacteria with initial concentration of 1×10~8 CFU/m L were inoculated into different concentrations of nicosulfuron soil and cultured at 30 ? for 28 d,the results showed that the degradation rateof nicosulfuron at the concentration of 1 mg/kg was the highest.84%,the results show that in the process of soil remediation,the degradation effect is better when the concentration of the inoculated strain is larger.When the concentration of nicosulfuron is low,the herbicide is easily degraded,and the high concentration of nicosulfuron may inhibit the degradation of the strain.The overall results showed that the strain TYM-1 had a certain repairing effect on the indoor simulated contaminated soil,and had strong degradation ability.It has a good application prospect in the repair of nicosulfuron-contaminated soil.