Characteristics of the Arsenic-Methylating Bacterium Cellulomonas sp. Strain K63

Biomethylation of arsenic is usually considered as a detoxification of arsenic because toxicity of most organic methylated arsenic is much less than that of inorganic arsenic. We investigated the feasibility of a novel bioremediation using an arsenic methylating bacterium. An arsenic methylating bacterium Cellulomonas sp. strain K63, isolated from soil in Miyazaki, was evaluated for growth characteristics and arsenic metabolism. The growth of strain K63 was inhibited in 200 mg As/L arsenic medium. Strain K63 metabolized arsenite (<50.0 mg As/L) to nonvolatile species such as monomethylarsonic acid, dimethylarsinic acid, trimethylarsenic oxide and arsenobetaine effectively. The percent of organic methylated arsenic excreted into the medium by strain K63 showed 90.1% of total arsenic compounds when strain K63 was cultured aerobically in the medium containing 5.0 mg As/L of arsenite for five days.