Abstract

Chlorpyrifos (Chlp), one of the major organophosphates is extensively used in agriculture to control pests. With a half-life of 7–120 d, it may persist for up to one year in soil depending on the soil conditions and affect the soil microflora. Chlp degradation by soil microbes proves to be an effective and environment friendly method to remove it from the soil. This study aims to identify and characterize Chlp degrading soil microbes. Total 173 bacteria isolated from different soil samples were screened for Chlp degradation. Characterization of 10 selected samples showed that all the strains produced excessive exo-polysaccharides (EPSs), which positively correlated with the Chlp degradation under in vitro conditions. Among these 10 bacterial strains, the most potent Chlp degrading bacteria was identified to be Alcaligenes faecalis (NBRI OSS2-5) which paired with the Chlp degrading Pseudomonas in the phylogenetic tree. The strain was shown to possess opd gene reported for Chlp degradation. From the study, it was concluded that EPS production may be a common feature of Chlp degrading microbes which may have some role in the Chlp biodegradation process and the pesticide-contaminated fields may not necessarily be the ideal source of isolating pesticide degrading microbes.

摘要

毒死rif（Chlp）是主要的有机磷酸盐之一，已广泛用于农业以控制害虫。半衰期为7–120 d，根据土壤条件的不同，它在土壤中可能可持续长达一年，并影响土壤微生物区系。事实证明，土壤微生物对Chlp的降解是一种有效且环保的方法，可将其从土壤中去除。这项研究旨在鉴定和表征Chlp降解土壤微生物。从不同土壤样品中分离出的总共173种细菌进行了Chlp降解筛选。对10个选定样品的表征表明，所有菌株均产生过量的外多糖（EPS），与体外Chlp降解呈正相关情况。在这10个细菌菌株中，最有力的Chlp降解细菌被鉴定为粪便产碱菌（NBRI OSS2-5），它与系统发育树中的Chlp降解假单胞菌配对。显示该菌株具有报道的Chlp降解的opd基因。从研究中可以得出结论，EPS的产生可能是Chlp降解微生物的共同特征，可能在Chlp生物降解过程中起一定作用，而农药污染的田地不一定是分离农药降解微生物的理想来源。