Identification and degradation characteristics of a napropamide-degrading bacterium strain

Abstract

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.