Abstract

A strain CSCr-3 with high Cr(VI)-reducing ability under alkaline conditions was isolated from a chromium landfill and identified as Ochrobactrum sp. on the basis of 16S rRNA gene sequence analysis. The cells were rod shaped, Gram-negative and motile. The physiological characteristics and Cr(VI)-reduction of the strain were also studied. The results showed that the Ochrobactrum sp. strain CSCr-3 was tolerant to very high concentration of Cr(VI) (800 mg/L) and capable of reducing different forms of Cr(VI) (chromate and dichromate), under a wide range of temperatures (25-40 degrees C) and pH (7-11) with optimum at 35 degrees C and initial pH 10. Higher rates of Cr(VI)-reduction were observed with higher initial cell and Cr(VI) concentrations. Strain CSCr-3 could reduce Cr(VI) very efficiently over a wide range of Cr(VI) concentrations (100-800 mg/L). The addition of glucose caused a dramatic increase in Cr(VI)-reduction by Ochrobactrum sp. CSCr-3, while the presence of sulfate or nitrate had no influence. The presence of other metals, such as Cu, Co, Mn, etc., significantly stimulated Cr(VI)-reduction ability by the strain CSCr-3. The results obtained in this study have significance for the bioremediation of chromate pollution.