Characterization of a bacterial consortium mineralizing isoproturon (IPU)

A bacterial consortium, isolated from a French agricultural soil, was shown to rapidly mineralize the phenylurea herbicide isoproturon (3-(4-isopropylphenyl)-1,1-dimethylurea). Study of the mineralization kinetics by ultra performance liquid chromatography (UPLC)had shown the transitory accumulation and degradation of the three known isoproturon metabolites 3-(4-isopropylphenyl)-1-methylurea, 3-(4-isopropylphenyl)-urea, and 4-isopropylaniline, thus indicating a metabolic pathway initiated by two successive N-demethylations, followed by cleavage of the urea side chain. This bacterial consortium did not degrade other phenylurea herbicides like diuron, linuron, monolinuron and chlorotoluron suggesting the existence of pathway specific for IPU. Six bacterial strains were isolated from the consortium by successive inoculations on mineral salt medium but none of them was able to degrade isoproturon in isolated form. Based on partial sequencing of the 16S rDNA sequence, the isolated bacterial strains were found to be belonging to genera Ancylobacter, Pseudomonas, Stenotrophomonas, Methylobacterium, variovorax and Agrobacterium. A BAC genomic library was established and is currently under functional screeing searching for BAC clone harbouring IPU-degrading capability. positive BAC clone will then be fully sequenced for identifying gene coding for the enzyme responsible for IPU transformation which up to now remains unknown