Two thermophilic Bacillus cereus strains (B. cereus-TA2 and B. cereus-TA4) used in the present study were isolated from the geothermal spring of Hunza valley, Gilgit, Pakistan. They showed the ability to withstand and grow at high temperature (85°C). Both these strains could resist multiple metals (copper, cadmium, mercury, manganese, zinc, arsenic, chromium and selenium). Strain B. cereus-TA4 reduced Cr (VI) at pH 5.0 to 9.0 but maximum reduction (83%) was observed at pH 7.0 after 48 h when initially supplied with 200 µg mL-1 of K2CrO4. Lower initial concentrations such as 100 µg mL-1 supported higher reduction (90 to 95%) than that of high concentration such as 500 µg mL-1 (20 to 30%). Both the strains reduced nearly 70% of Se (IV) after 48 h of growth at pH 7.0 when initially supplied with 200 µg mL-1 of Na2SeO3. The optimum temperature for maximum Se (IV) reduction was 45°C for both the strains.
chromium; bioremediation; selenium; heavy metals
