The metabolic pathway of metamifop degradation by consortium ME-1 and its bacterial community structure

Metamifop is universally used in agriculture as a post-emergence aryloxyphenoxy propionate herbicide (AOPP), however its microbial degradation mechanism remains unclear. Consortium ME-1 isolated from AOPP-contaminated soil can degrade metamifop completely after 6 days and utilize it as the carbon source for bacterial growth. Meanwhile, consortium ME-1 possessed the ability to degrade metamifop stably under a wide range of pH (6.0–10.0) or temperature (20–42 °C). HPLC–MS analysis shows that N-(2-fluorophenyl)-2-(4-hydroxyphenoxy)-N-methyl propionamide, 2-(4-hydroxyphenoxy)-propionic acid, 6-chloro-2-benzoxazolinone and N-methyl-2-fluoroaniline, were detected and identified as four intermediate metabolites. Based on the metabolites identified, a putative metabolic pathway of metamifop was proposed for the first time. In addition, the consortium ME-1 was also able to transform or degrade other AOPP such as fenoxaprop-p-ethyl, clodinafop-propargyl, quizalofop-p-ethyl and cyhalofop-butyl. Moreover, the community structure of ME-1 with lower microbial diversity compared with the initial soil sample was investigated by high throughput sequencing. β-Proteobacteria and Sphingobacteria were the largest class with sequence percentages of 46.6% and 27.55% at the class level. In addition, 50 genera were classified in consortium ME-1, of which Methylobacillus, Sphingobacterium, Bordetella and Flavobacterium were the dominant genera with sequence percentages of 25.79, 25.61, 14.68 and 9.55%, respectively.