Kinetics of arsenite oxidation by Variovorax sp MM-1 isolated from a soil and identification of arsenite oxidase gene

A Gram-negative, arsenite-oxidizing bacterial strain, MM-1 tolerant to 20 mM arsenite and 200 mM arsenate was isolated from a heavy metal contaminated soil which contained only 8.8 mg kg(-1) of arsenic. Based on 16S rRNA analysis, the strain was closely related to the genus Variovorax. This strain completely oxidized 500 mu M of arsenite to arsenate within 3 h of incubation in minimal salts medium. Kinetic studies of arsenite oxidation by the cells showed one of the lowest K-m (17 mu M) and highest V-max (1.23 x 10(-7) mu M min(-1) cell(-1)) values reported to date for whole cell suspension. PCR analysis using degenerate primers confirmed the presence of arsenite oxidase gene and its amino acid sequence was 70-91% identical to the large subunit of most reported arsenite oxidases. The significant arsenite oxidation capacity shown by the strain opens the way to its potential application in arsenic remediation process. (C) 2012 Elsevier B.V. All rights reserved.