乙草胺降解菌Sphingomonas sp. DC\|6的分离鉴定及其代谢途径的初步研究

从生产乙草胺的农药厂排污口污泥中分离到一株乙草胺降解菌，命名为DC\|6。根据形态特征、生理生化特性以及16S rDNA系统发育分析，初步鉴定其为鞘氨醇单胞菌属(Sphingomonas sp.)。该菌能够降解甲草胺、乙草胺和丁草胺，而对于异丙甲草胺、丙草胺和异丙草胺却没有任何降解效果，48 h对丁草胺、乙草胺和甲草胺的降解率分别为76.7%、93.6%和98.6%，对甲草胺的降解效率最高，而对丁草胺的降解效率最低，表明侧链烷基长短影响着该类除草剂的降解速率，随着侧链基团碳原子的增加以及支链的增多降解效率呈下降的趋势。通过气相色谱-质谱鉴定了该菌降解乙草胺的代谢产物并分析了乙草胺的代谢途径，发现乙草胺首先N\|脱烷基形成2\|氯\|N\|(2\|乙基\|6\|甲基苯基)乙酰胺（CMEPA），然后水解生成苯胺衍生物2\|乙基\|6\|甲基苯胺（MEA），MEA能够进一步完全降解。但苯胺类化合物降解途径中的关键酶苯胺双加氧酶没有参与MEA降解代谢，表明菌株DC\|6对MEA的降解不同于已报道苯胺降解途径。

Isolation and Characterization of Acetochlor\|degrading Strain Sphingomonas sp. DC\|6 and Preliminary Studies on its Metabolic Pathway

An acetochlor herbicides\|degrading strain, designated as DC\|6, was isolated from activated sludge of the wastewater outfall of a factory from Kunshan City. According to the morphological, physiological and biochemical characteristics and the phylogenetic analysis of 16S rDNA sequence, the strain was identified preliminarily as Sphingomonas sp.. Strain DC\|6 could degrade alachlor，acetochlor and butachlor, but could not degrade metolachlor, pretilachlor and propisochlor. Within 48 hours of incubation, about 76.7% of butachlor, 93.6% of acetochlor and 986% of alachlor were degraded by strain DC\|6, respectively. The degradation rates followed the order of alachlor > acetochlor > butachlor. These results indicated that the factors influencing the biodegradability of these herbicides were the length and complicated of amide nitrogens alkoxymethyl: the longer and more complicated the alkyl was, the slower the degradation efficiencies occurred. The pathway of acetochlor degradation was elucidated based on the results of metabolites identification by GC\|MS. Acetochlor was firstly degraded to 2\|chloro\|N\|(2\|methyl\|6\|ethyl) phenyl\|acetamide (CMEPA) by N\|dealkylation, and then it subsequently transformed to 2\|methyl\|6\|ethylaniline (MEA). MEA was further completely degraded via unknown metabolites. However, aniline dioxygenase, which was the key enzyme in the degradation of aniline and aniline derivatives, did not involve in the degradation of MEA. This indicated that the degradation of MEA by strain DC\|6 was different from the reported aniline degradation pathway.