Evaluation of Heavy Metals Resistant Micrococcus sp. Isolated from Rivers in Basra, Iraq

The present study aims to isolation, identification and characterization of heavy metal resistant bacteria from six rivers in Basra Southern Iraq. Two species of Micrococcus (M. halobius and M. kristinae) were isolated on the basis of morphological and biochemical profiles and selected based on high levels of heavy metals (cadmium, lead, copper and nickel) resistance. The concentrations of dissolved heavy metals (Cd, Pb, Cu and Ni) in rivers were determined. The maximum tolerance concentration (MTC) of isolates against Pb, Cu, Cd and Ni was determined in solid media after 72 h incubation. All isolates were resistant to Pb (2200-2600) μg mL-1, Cu (400) μg mL-1, Cd (300-400) μg mL-1 and Ni (200-300) μg ml-1. Living biomass of M. halobius and M. kristinae were used for the removal of heavy metal ions at different concentrations (25, 50 and 100) μg mL-1 from aqueous metal solutions. The best concentration of removal was 25 μg mL-1 after 72 h incubation at 120 rpm. Percent removal efficiency of M. kristinae was 47.22, 26.26 for Cu and Pb respectively, and for M. halobius was 31.52, 27.87 for Cd and Ni respectively.