Methamidophos (O,S-dimethyl phosphoramidothioate) is a widely used organophosphorus insecticide. Because of its persistence and toxicity, its use has been prohibited or restricted in several countries. Thus its biodegradation is of interest ([http://www.ncbi.nlm.nih.gov/pubmed/19960233|Wang et al., 2010]). Hyphomicrobium sp. MAP-1 can utilize methamidophos as its sole carbon, nitrogen, and phosphorous source for growth. The first step in the pathway is cleavage of the P-N bond to form O,S-dimethyl hydrogen thiophosphate. This is hydrolyzed at either the P-O bond to form S-methyl dihydrogen thiophosphate, or the P-S bond to form methyl dihydrogen phosphate. It is proposed that these last two compounds are further hydrolyzed to phosphate ([http://www.ncbi.nlm.nih.gov/pubmed/19960233|Wang et al., 2010]).