Removal of lead and cadmium by halophilic bacteria isolated from the Dead Sea shore, Jordan

Ten Gram-positive and Gram-negative bacterial cultures were recovered from nine water, mud, and soil samples from the Dead Sea shore at Suwaymah. They were able to grow at 10% NaCl and at 45 degrees C. Bacterial cultures 6 and 8 were able to grow in nutrient media supplemented with 2250 ppm of Pb. Bacterial cultures 1, 3-6, 9, and 10 were able to grow in nutrient medium supplemented with 1000 ppm of Cd. Atomic absorption spectrometry was used to estimate the absorbed Pb and Cd by bacterial cultures from 5-, 25-, 100-, and 500-ppm stock solutions of both elements. After 2 wk, the results showed that the maximum absorption for Pb was achieved by culture 6 in the following percentages: 79.8%, 70.48%, 89.48%, and 83.39%, respectively. The maximum absorption of the same concentration of Cd was achieved by culture 9 with the following percentages: 69.2%, 32.24%, 44.98%, and 60.0%, respectively. After 3 wk of incubation, the estimated absorption of both heavy metals was achieved by the same cultures (6 and 9), respectively, in the following percentages: 86.8%, 76.72%, 96.25%, and 96.0% for Pb and 82.60%, 93.2%, 92.74%, and 89.79% for Cd. The accumulation of the absorbed metals was found to be maximum in the protoplast of all the cultures. The accumulation at the cell wall was maximum in culture 2, and between the cell wall and the plasma membrane, it was maximum in cultures 2 and 8 for Pb and Cd, respectively.