الفهرس Only 14 pages are availabe for public view
 |  | from | 187 |  |  |
| | | from | 187 | | |
Abstract
Pollution of various metals shown to be related to development of bacterial strains capable of tolerating such metal ions, among these contaminants mercury is one of the leading chemicals of pollution in industrialized zones. With the intention of screening for mercury resistance, a total of 70 bacterial isolates including 30 environmental bacterial isolates and 40 clinical Gram-negative isolates were selected for their ability to grow in presence of 50æM HgCl2 and considered to be mercury resistant isolates. Mercury resistance was detected in twenty species from twelve different bacterial genera. The identification result showed that 93% of the isolated bacteria were Gram-negative bacteria and Escherichia coli was the most abundant (32.9%) followed by Klebsiella pneumonia (17.1%) and Proteus mirabilis (10%). MICs of HgCl₂ were equal to 400 oM for more than 50% of the isolates, mainly clinical isolates. 57% of the isolated bacterial culture could remove more than 90% of mercury from liquid culture media containing HgCl₂ (50 oM) after 16 hours of incubation. Twenty one (30%) Gram-negative bacteria were found to tolerate increasing concentration of mercury by serial passage up to a concentration of 400 oM in liquid medium. Most of our isolates possess the mer operon in their genome, which enables them to survive in the presence of mercury