Supplementary material from: Genetic characterization of the ibuprofen degradative pathway of Rhizorhabdus wittichii MPO218

Abstract

Ibuprofen is one of the most common drugs found as contaminants in soils, sediments and waters. Although several microorganisms able to metabolize ibuprofen have been described, the metabolic pathways and factors limiting biodegradation in nature remain poorly characterized. Among the bacteria able to grow on ibuprofen, three different strains belonging to Sphingomonadaceae and isolated from different geographical locations, carry the same set of genes required for the upper part of the ibuprofen metabolic pathway. Here, we have studied the metabolic pathway of Rhizorhabdus wittichii MPO218, identifying new genes required for the lower part of the ibuprofen metabolic pathway. We have identified two new DNA regions in MPO218 involved in the metabolism of ibuprofen. One is located on the MPO218 chromosome and appears to be required for the metabolism of propionyl-CoA through the methylmalonyl-CoA pathway. Although involved in ibuprofen metabolism, this region is not strictly necessary for growing using ibuprofen. The second region belongs to the pIBU218 plasmid and comprises two gene clusters containing aromatic compounds biodegradation genes, part of which are necessary to ibuprofen degradation. We have identified two genes required for the first two steps of the lower part of the ibuprofen metabolic pathway (ipfL and ipfM) and, based on our results, we propose the putative complete pathway for ibuprofen metabolism in strain MPO218.