一株小飞蓬内生毒死蜱降解菌的分离鉴定及其降解特性初探

Isolation and identification of a chlorpyrifos degrading endophyte from Conyza canadensis(L.) Cronq and its degradation characteristics

为分离筛选具有毒死蜱降解特性的植物内生菌,从农药厂废液池旁采集小飞蓬植物样本,经表面消毒后研磨提取植物汁液,通过以毒死蜱作为单一碳源的无机盐培养基(MSM)进行连续5代培养筛选,获得一株植物内生细菌XFP-gy,经生理生化试验及16Sr DNA同源性比对分析,初步鉴定该菌属阪崎克罗诺杆菌属(Cronobacter sp.)。将菌株XFP-gy在以毒死蜱(初始质量浓度为20 mg/L)为单一碳源的MSM中培养,至第6天时达生长高峰,第9天时毒死蜱的降解率为77.28%。在M SM培养基中补充牛肉膏和蛋白胨(加富培养基)可以促进菌株XFP-gy的生长,并将其对毒死蜱第5天的降解率由69.59%提高到98.0%。菌株XFP-gy降解毒死蜱的最佳培养条件为30℃和p H 7.0,在此条件下,增加培养液中原始接菌量,降低底物毒死蜱的初始质量浓度,可明显提高XFP-gy对毒死蜱的降解效率,当毒死蜱初始质量浓度为10 mg/L,原始接菌量为2%时,至第9天时在培养液中未检出毒死蜱残留。

In order to isolate and screen plant endophytes capable of degrading chlorpyrifos, horseweed herb（ Conyza canadensis（ L. ） Cronq） collected near the waste pool of a pesticide factory was used as target plant. After surface sterilization, the plant tissues were triturated to obtain plant juice. The plant edophytes were screended by plating the plant juice on minimal salts media （MSM） modified with chlorpyrifos as the sole carbon. After 5 times successive screening, a strain named as XFP-gy capable of degrading chlorpyrifos was isolated. It was identified as Cronobacter sp. based on its physiologicalbiochemical characteristics and 16SrDNA sequence. The growth of strain XFP-gy reached the maximum at the 6th day in liquid MSM with initial chlorpyrifos concentration of 20 mg/L, and 77.28 % chlorpyrifos was degraded after 9 days＇ inoculation. The degradation rate could be enhanced up to 98.0% at the 5th day by adding beef extract and peptone in MSM. The optimal temperature for XFP-gy degrading chlorpyrifos is 30 ~C, and the optimal pH value is 7.0. Under optimal incubation condition, the chlorpyrifos degradation efficiency increased with the increasing initial bacterium inoculum amount, and the decreasing substrate （chlorpyrifos） concentration in the media. No chlorpyrifos was detected at the 9th day when the initial inoculum of XFP-gy was 2% and concentration of chlorpyrifos was 10 mg/L.