Imazamox microbial degradation by common clinical bacteria: Acinetobacter baumannii IB5 isolated from black soil in China shows high potency

Herbicidal residues of imazamox are hazardous to some sensitive rotational aftercrops. The aim of the study was to isolate and identify a microbial strain capable of degrading imazamox. The strain IB5, capable of efficiently degrading imazamox, was isolated from an imazamox-contaminated soybean field in Heilongjiang Province, China. It was found to degrade 98.61% of 400 mg L−1 imazamox within 48 h by high-performance liquid chromatograph. Through morphological, physiological and biochemical characterization, and the 16S rDNA sequencing, the strain was identified as Acinetobacter baumannii. An optimal degradation condition was obtained and verified: 400 mg L−1 imazamox, 0.1% (volume ratio) initial inoculum, 37°C and pH 7.0. Four main products were captured in the liquid chromatograms and mass spectra, and a pathway for imazamox degradation by IB5 was proposed. This work provides a new suitable candidate for imazamox biodegradation and theoretical evidence for imazamox residue bioremediation. A. baumannii is a common clinical bacteria, but its imazamox-degrading feature has not been reported previously.