| Pesticides are important to increase agricultural yield. But the pollution has harmed seriously the environment and people's health. Organophosphorus pesticides are used widely for the control of insects all over the world; methyl parathion is a typical one of them, but they are neurotoxin to human and animal. Microbial process is found an effective way to detoxify the compounds. It is practical to isolate microorganisms that can degrade organic phosphorus, to study their characterization, and to clone the degradation genes then use them to degrade the pollution. Through chemo taxonomic characterizations and phylogenetic inference based on 16s rDNA sequence and analysis, we identified two strains of bacteria X-13 and X-20 isolated from activated sludge of Huayang Pesticide Factory in 2001. The results are: X-13 belongs to Bacillus subtilis; X-20 belongs to a member of Alcaligenes and is named as Alcaligenes.sp.YcX-20, the genus GenBank accession number of the 16s rDNA sequence is AY628412. Enzyme degraded for methyl-parathion belongs to family of phosphorus esterase. Esterase activity of the strains increases with concentration of cell dose and has derect correlation with culture time. It can grow with methyl parathion as sole carbon source and was degraded to p-nitro phenol so to reduce its toxicity for 100~200 times. In rich culture the strains can utilize methyl parathion better. The strain X-20 can tolerate high concentration methyl parathion of 500mg/L with basic medium and up to 900mg/L with ordinary medium while X-13 only 150mg/L and 300mg/L. Detected the remained methyl parathion of 50mg/L with basic culture after 30 hour, at 30℃, pH7.0 with Gas Chromatography, and found 50% was hydrolyzed. It's possible that the two strains have no degradation plasmid and the degradation genes come from chromosome because we failed to get any plasmid from them although tried different isolated methods. The next we'll...
|
PDF Full Text Request