Reduction of toxic hexavalent chromium by Ochrobactrum intermedium strain SDCr-5 stimulated by heavy metals

A Cr(VI) resistant bacterial strain SDCr-5, identified as Ochrobactrum intermedium on the basis of 16S rRNA gene sequencing, was tolerant to high concentrations of Cr(VI) up to 15 mg ml−1 in acetate minimal medium. O. intermedium SDCr-5 reduced Cr(VI) under a wide range of concentrations from 100 to 1500 μg ml−1 and reduction was optimum at 37 °C and pH 7. It reduced 200 and 721 μg ml−1 Cr(VI) within 72 and 96 h, respectively. The rate of Cr(VI) reduction increased with concentration from 100 to 1500 μg ml−1. The presence of heavy metal cations such as Cu2+, Co2+, Mn2+ and Ni2+ stimulated Cr(VI) reduction. Strain SDCr-5 might be useful for Cr(VI) detoxification under a wide range of environmental conditions.