Syntrophic biodegradation of propoxur by Pseudaminobacter sp. SP1a and Nocardioides sp. SP1b isolated from agricultural soil

Abstract

Three pairs of syntrophic bacteria involved in degradation of the N-methylcarbamate insecticide propoxur were isolated from agricultural soils. All pairs were able to use propoxur as a sole carbon and energy source. Among these pairs, SP1 degraded propoxur most rapidly and was chosen for further studies. Based on 16S rRNA gene sequence analysis, the members of SP1 were related to members of genera Pseudaminobacter and Nocardioides. SP1 completely degraded propoxur through syntrophic interaction without any identifiable products. The syntrophic strain SP1a appeared to convert propoxur to 2-isopropoxyphenol (2-IPP), which was subsequently degraded by strain SP1b, as observed by gas chromatography-mass spectrometry (GC-MS). When analyzed by PCR for previously reported carbamate hydrolase genes, strain SP1a showed homology with a cehA gene encoding carbaryl hydrolase. This is the first study to report that syntrophic metabolism by two bacterial strains completely degraded propoxur.