一株敌草胺降解菌的分离鉴定及降解性能

为探讨酰胺类除草剂敌草胺的微生物降解机理和土壤中敌草胺降解的生物强化性能,从长期使用敌草胺的烟田土壤中分离到一株敌草胺降解细菌菌株,命名为LGY06.经形态特征、生理生化特性及16S rDNA序列分析将其鉴定为蜡状芽孢杆菌.在纯培养条件下,菌株LGY06对敌草胺的降解符合一级动力学特征,7 d内对50 mg·L^-1敌草胺降解率达到75.7%;LGY06降解敌草胺的最适温度和最适pH值分别为35 ℃和8.0.通过气相色谱-质谱鉴定了菌株LGY06降解敌草胺的降解产物并分析了其降解途径,α-萘酚和丙酰胺是主要的降解产物,LGY06对敌草胺的作用方式主要有脱烷基、氧化(或水解),为矿化过程.室内模拟条件下,LGY06能有效促进土壤中敌草胺残留的降解,与未接种灭菌土、非根际土和根际土相比,敌草胺在接种LGY06土壤中的降解半衰期分别缩短了79.5%、36.6%和41.1%.

Identification and degradation characteristics of a napropamide-degrading bacterium strain

In order to investigate the microbial degradation mechanism of amide herbicide napropamide and its degradation bioaugmentation in soil, a bacterial strain LGY06 capable of utilizing napropamide as sole carbon and energy source was isolated from a tobacco-planted soil after successive application of napropamide. LGY06 was identified as Bacillus cereus based on morphological, physiological and biochemical characteristics, and the 16S rDNA homologue sequence analysis. The degradation of napropamide in pure cultures by LGY06 was fitted to the first-order function. The strain LGY06 could degrade more than 75.7% of 50 mg·L^-1 napropamide within 7 d. The optimal temperature and pH for napropamide degradation was 35 ℃ and 8.0, respectively. The pathway of napropamide degradation was elucidated based on metabolites identification by GC-MS. The main degradation products of napropamide by LGY06 were α-naphthol and propylacetanilide. The meta-bolism of napropamide by strain LGY06 involved dealkylation and oxidation (or hydrolyzation). Under the laboratory control conditions, the bacterial strain LGY06 could effectively enhance the degradation of napropamide in soil. Compared with the un-inoculated controls, the half-life of napropamide in sterilized soil, non-rhizosphere soil, and rhizosphere soil inoculated with the strain LGY06 was shorted by 79.5%, 36.6% and 41.1%, respectively.