茶叶上拟除虫菊酯类农药降解菌的分离及其特性

Isolation and character of synthetic pyrethroid insecticides-degrading bacteria from tea leaves

生物修复对降解污染基质中的农药是一种对环境有益的方法。目标是要寻找能够降解在茶叶生产中使用的拟除虫菊酯类农药的降解菌。最终在福州某茶园经农药处理过的茶叶中分离降解菌。首先在富集培养基中筛选,接着在以农药为唯一碳源的基础培养基中连续筛选。结果发现,其中一株标号为c1f6的菌株生长的特别良好,经AMS-VITEK120全自动微生物分析系统鉴定,为假单胞菌属的一个未知种。采用HP6890气相色谱仪测定菌株对拟除虫菊酯类农药联苯菊酯、甲氰菊酯和氯氰菊酯的降解率。在pH7.0的基础培养基发酵液中,以各加100mg·L-1这3种农药为唯一碳源,30℃振荡培养,接种c1f6后3d,这3种农药的降解率分别为55.64%、44.56%和52.19%。采用光密度测定的菌株生长值和农药降解率的关系曲线表明,在基础培养基中,农药降解和菌株生长成正相关,说明菌株能以拟除虫菊酯类农药为唯一碳源和能源进行生长。采用同样的方法测定表明,菌株c1f6对有机磷农药也有一定的降解力,3d对甲胺磷和毒死蜱的降解率分别为27.67%和12.35%。因此,假单胞菌c1f6是一株较广谱的农药降解菌,有望用于生物修复过程,以减少茶叶栽培过程中的产品和环境污染。

Bioremediation is an environmentally benign method for degrading insecticides from contaminated substrates. Our goal was to find bacteria that could degrade the pyrethroids that are used in production of tea. To this end, we isolated bacteria from pesticide-treated tea leaves from the tea garden in Fuzhou, Fujian Province, China. Initial screening was on enrichment media, with subsequent sequential isolation on minimal media containing the pesticides as sole C source. One strain which grew particularly well （designated clf6） was Pseudornonas sp., identified with a AMS-VITEK120 whole-auto-microbial analysis system. We then used gas chromatography （HP 6890） to measure the rates of disappearance of the pyrethroids bifenthrin, fenpropathrin and cypermethrin from pH 7, liquid cultures maintained aerobically at 30C. Other than 100mg·L^-1 of each of the pesticides, the media were carbon-free. Three days after inoculation with clf6 the concentrations of the three chemicals had decreased by 55.64%, 44.56% and 52.19% respectively. Growth measured as optical density showed a positive correlation to the amount of pesticide removed, suggesting the bacteria used these pyrethroids as carbon and energy sources. Using the same methods, we showed that clf6 could also degrade the organophosphorus pesticides methamidophos and chlorpyrifos, 27.67 and 12.35% being degraded respectively, after 3 days. Since Pseudornonas sp. clf6 can degrade a broad spectrum of pesticides, it should be able to use it in a bioremediation process to minimize contamination of the product and the environment during tea cultivation.