Degradation of arylarsenic compounds by microorganisms

Microorganisms were not directly accumulated when soil contaminated to about 0.5 mM with diphenylarsinic acid (DPAA) was used as the sole source of carbon. However, using toluene as the carbon source yielded several isolates, which were then used in cultivation with DPAA as the sole source of carbon. By these methods, Kytococcus sedentarius strain NK0508, which can grow in up to 0.038 mM DPAA, was isolated. The toxicity of DPAA retarded the growth of K. sedentarius and the direct accumulation of DPAA-utilizing microorganisms from environmental samples. This strain can utilize about 80% of DPAA and phenylarsonic acid as the sole source of carbon for 3 days. Degradation products of DPAA were determined to be cis, cis, muconate and arsenic acid. When K. sedentarius was cultivated with methylphenylarsinic acid and diphenylmethylarsine, about 90% and 10% degradation of the two compounds, respectively, were observed. Diphenylmethylarsine oxide, possibly synthesized by methylation of DPAA, was detected as one of the transformation products. These results suggest that degradation is initiated by splitting of the phenyl groups from the arylarsenic compounds with subsequent hydroxylation of the phenyl groups and ring opening to yield cis, cis, muconate.