两株毒死蜱降解细菌的分离鉴定及其降解特性

The isolation,identification and degradation characteristics of two chlorpyrifos degrading bacteria

采用富集培养的方法,从农药生产企业的废水处理系统中分离驯化出两株能够降解毒死蜱的菌株HY-2与HY-4,在形态特征和生理生化分析的基础上,又对其16SrDNA序列进行了分析,并研究了其对毒死蜱和其它有机磷农药的降解特性.结果表明,2个菌株均属蜡状芽孢杆菌(Bacilluscereus),HY-4对毒死蜱的降解能力大于HY-2.2个菌株降解毒死蜱的适宜条件为:外加葡萄糖浓度3g.L-1,培养温度35℃,初始pH值8.0,毒死蜱初始浓度80mg·mL-1,接种量20%(体积比,菌体密度:稀释到所配菌悬母液(OD600=2)的0.5倍).酵母膏含量对降解的影响表明,当添加3g.L-1的葡萄糖时,最适的酵母膏含量为1g.L-1,而不添加葡萄糖时,最适的酵母膏含量为5g.L-1.2个菌株对甲基对硫磷的降解研究发现,HY-2和HY-4对初始浓度为100mg·mL-1的甲基对硫磷60h的降解率分别达64.7%和88.7%;然而,2个菌株对初始浓度为100mg·mL-1的三唑磷60h的降解率仅为13.3%～14.2%,降解率较低.

Chlorpyrifos is used extensively on farmland and contributes to environmental pollution. Biodegradation is regarded as an alternative method to remove chlorpyrifos from the contaminated sites. In this study, two strains of bacteria designated HY-2 and HY-4, were isolated from the wastewater treatment system of a pesticide enterprise. The traditional morphology, physio - biochemical characteristics as well as 16S rDNA gene sequence analysis were applied to classify the bacteria and their characteristics of degrading chlorpyrifos and other organophosphorus pesticides were also studied. Strains HY-2 and HY-4 were both identified as Bacillus cereus, and the degradation efficiency of HY-4 was greater than that of HY-2. The optimal conditions for degradation of chlorpyrifos by the two strains were as follows： glucose concentration 3 g· L^-1, initial pH 8.0, 35℃, initial chlorpyrifos concentration 80 mg· L^-1 and 20% inoculation amount （Volume ratio, cell density： 1/2 dilution of the bacteria suspension （ OD600 = 2） ）. The optimum content of yeast extract was 1 g· L^- 1 when the concentration of the glucose was 3 g·L^-1 but the optimal concentration of the yeast extract was 5 g· L^ -1 when the medium did not contain glucose. The methyl - parathion degradation rate of HY-2 and HY-4 reached 64.7% and 88.7% within 60 h, respectively （from an initial concentration of 100 mg· L^-1 methyl-parathion）. But the degradation rate of triazophos was relatively lower than that of the other two pesticides. The triazophos degradation rates were from 13.3% to 14.2% within 60 h when the medium contained 100 mg·L^-1 triazophos.