Characterization of a Cd(2+)-resistant strain of Ochrobactrum sp. isolated from slag disposal site of an iron and steel factory.

A cadmium-resistant bacterium designated as CdSP9 was isolated from the slag disposal site of IISCO, Burnpur, West Bengal, India. The isolate was identified as Ochrobactrum sp. on the basis of 16S rDNA sequence-based molecular phylogenetic approach and phenotypic characteristics. It is a Gram negative, short rod (0.5-1.0 micro), aerobic bacterium, growing well in LB medium between temperatures 10-42 degrees C, pH 6.0-9.0, and between 2 and 6% NaCl. The most preferred nitrogen and carbon sources for the strain are L: -proline, L: -lysine and fructose, maltose, respectively. Superoxide toxicity minimization by increased level of SOD activity also occurs in this bacterium. The heavy metal accumulation efficiency as determined by atomic absorption spectroscopy was found to be 0.214 mg/g of the dry weight at late log phase. The accumulation efficiency was directly proportional to the optimum growth conditions.