Isolation&Characterization Of A Butachlor Degrading Strain Flavobacterium Yanchengense Sp. Nov.Hg~T And Its Characteristics

Butachlor is a selective preemergent chloroacetamid herbicide used to control graminaceous annual grasses. With the excellent characteristics of high activity and strong selectivity, it has been become one of the three kinds of herbicides that are the most widely used in China. Due to the wide use of butachlor and the formation of its residues, it has caused a great threat to human health and ecological environment. Bioremediation based on the microbial degradation has great significance in the elimination of organic pollution.A butachlor-degrading bacterial strain, designated as hg, was isolated from activated sludge of a wastewater treating system in a butachlor manufacturing company by the enrichment culture technique. Strain hg could utilize butachlor as carbon source for its growth, and the degradation efficiency against100mg-L-1butachlor was80%within3d. The optimal temperature for the degradation and pH were30℃and7.0, respectively. The degradation efficiency of butachlor showed a positive corelation to the inoculation level. With the increasing of initial concentration of butachlor, the degradation efficiency decreased. The addition of exogenous nutrients can promote the degradation of butachlor. The degradation pathway of butachlor by strain hg was studied by metabolite identification. The result showed butachlor was degraded to2-Chloro-N-(2,6-diethylphenyl)-acetamide through butoxymethyl-dealkylation in strain hg.The16S rRNA gene sequence of strain hg showed highest similarity to Flavobacterium terrae R2A-13T(94.7%), which was less than97%and indicated that this strain might be a novel species of the genus Flavobacterium. So we carried out a detailed study on the biological characteristics and taxonomic status of the strain hg.Strain hg was a Gram-negative, good autotrophic, non-motile, non-spore-forming, and rod-shaped Flavobacterium-like bacterial strain. Colonies on TSA are yellow, circular, convex with entire margins. Oxidases and reductase were positive, but nitrate reduction, indole, urea enzyme reactions were negative. Strain hg grew optimally at pH7.0and30℃in the presence of1%(w/v) NaCl. It contained MK-6as the predominant menaquinone and iso-C15:0and iso-C17:03-OH as the major fatty acids. The polar lipids consisted of Phosphatidylethanolamine, unknown polar lipid, unknown phospholipid, unknown amino phospholipid, unknown glycolipid and unknown aminophospholipid. The DNA G+C content was34mol%. On the basis of phenotypic and phylogenetic distinctiveness, hg (=CCTCC AB2012099T=KACC16855T) was classified in the genus of Flavobacterium as the type strain of a novel species, for which the name Flavobacterium yanchengense sp. nov. is proposed.