Removal of soluble mercury by bacterial isolates

Abstract

Isolation and screening of 272 mercury-resistant bacterial strains from 61samples were performed and 259 of those strains were found to be able to transform soluble mercury or HgCl2 (aq) to volatile mercury or Hg (0). And 2 of 259 mercury-resistant (with volatilization ability) bacterial strain were selected, named HgR-11and HgR-14, identified biochemically and bacteriologically to possibly be Acinetobacter sp., and resistant to 250 microgrames per milliliter ((+,m)g/mL).Optimum conditions for growth of two selected strains in the presence of 5 ug/mL mercury (for induction), i.e., pH and temperature, were 8 and 35 degree Celsius ( C ) , respectively. In low mercury concentration (0, 4 or 8 ug/mL), there was no effect on growth, but longer lag phase was detected, and in high mercury concentration (100 and 150 ppm), the initial amounts of cells were reduced rapidly. Effect of pH and temperature on volatilization of mercury were conducted after24-hour incubation. The results indicated that mercury was removed from the medium exceeding to 98% at pH 7-9 and incubated from the medium at 25 40 C. In addition, the reduction of mercury concentration at difference time intervals was found and indicated that mercury concentrations were reduced rapidly in early incubation (0-2 hours). Therefore, the selected mercury resis6ttant bacterial strains may be suitable considerably to be used for further investigations in removal of soluble mercury.