Abstract It has been shown from diverse geographical locations that soils with repeated applications of pesticides display enhanced degradation of the pesticides which usually remain recalcitrant for a long time. In Kenya, agricultural activities have been using many different persistent pesticides for pest control. A study was undertaken to determine if the soils with repeated application history could show enhanced degradation of diuron. Laboratory degradation studies using non sterile sugarcane and pineapple-cultivated soils with over 5 years' application history showed enhanced degradation amounting to 80.2% and 86.2% of 5 mg/g initially applied diuron while sugarcane and pineapple-cultivated soils without application history degraded 34.4% and 48.4% of initially applied diuron after 146 days of incubation, respectively. Through liquid culture experiments with sugarcane and pineapple-cultivated soils and diuron as the carbon source, two bacterial strains capable of degrading diuron were isolated. By use of 16S rRNA comparative gene sequence technique, the strains were shown to be closely related to Bacillus muralis/Bacillus simplex and Bacillus pseudomycoides, respectively. These pure isolates were able to degrade diuron up to 51.0% and 54% of 50 mg/L after 46 days of incubation, respectively. The metabolites N-(3,4-dichlorophenyl)-N-methylurea and 3,4-dichloroaniline were reported as major by-products of diuron degradation in the two study sites with adapted microbes. The biodegradation capability of the strains isolated in this study indicates their microbial bioremediation potential for diuron mineralization in the contaminated soils.

中文翻译：

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从肯尼亚敌草隆污染的甘蔗和菠萝栽培土壤中分离的两种芽孢杆菌对敌草隆的降解作用增强

摘要 来自不同地理位置的研究表明，重复施用农药的土壤表现出对农药的降解增强，而这些农药通常会长时间保持顽固。在肯尼亚，农业活动一直使用多种不同的持久性杀虫剂来控制虫害。进行了一项研究，以确定重复使用历史的土壤是否会显示敌草隆的降解增强。使用具有超过 5 年应用历史的非无菌甘蔗和菠萝栽培土壤进行的实验室降解研究表明，初始施用 5 毫克/克敌草隆的降解率分别提高了 80.2% 和 86.2%，而没有施用历史的甘蔗和菠萝栽培土壤降解了 34.4%和 48.4% 的初始应用敌草隆分别在培养 146 天后。通过以甘蔗和菠萝栽培的土壤和敌草隆为碳源的液体培养实验，分离出了两种能够降解敌草隆的菌株。通过16S rRNA比较基因序列技术，显示这些菌株分别与壁画芽孢杆菌/单纯芽孢杆菌和假丝状芽孢杆菌密切相关。在培养 46 天后，这些纯分离株能够分别降解 51.0% 和 54% 的 50 mg/L 敌草隆。据报道，代谢物 N-(3,4-二氯苯基)-N-甲基脲和 3,4-二氯苯胺是两个具有适应微生物的研究地点降解敌草隆的主要副产物。本研究中分离的菌株的生物降解能力表明它们在污染土壤中对敌草隆矿化具有微生物生物修复潜力。