الفهرس 
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Abstract
An important microbial resistance mechanism to mercury is its reduction into elemental mercury (facilitated by the merA gene). This study aimed to: (i) isolate and characterize mercury resistant bacteria (MRB) with multi-resistance to many heavy metals; and (ii) investigate the presence and diversity of mercury resistance gene (merA), for their potential applications in mercuric bioremediation. Thirty eight microbial isolates from a variety of wastewater sources in Egypt were collected. Approximately 14 of the 38 isolates exhibited not only a high degree of tolerance to mercury (up to 160 ppm), but also a high resistance to other tested heavy metals [Cu, Co, Ni, and Zn]. from them, the 10 most resistant isolates were selected for further study and were found to include 9 Gram-negative and 1 Gram-positive bacterial strains. Multi antibiotic resistance profiles were recorded for 6 out of the 10 selected isolates. All the tested Gram-negative isolates (n=9) harbored a plasmid-encoded merA gene. The mercury removal effectiveness for the 10 selected isolates ranged between 50-99.9%, among which S. maltophilia ADW10 recorded the highest rate (99.9%; at an initial mercury concentration of 20 ppm). In conclusion, Beni Suef Governorate in Egypt, with its poorly investigated industrial and agricultural zones, may be considered as a good unexplored source for the isolation of many potential mercury resistant, as well as, multi-metal tolerant bacteria. Our results also demonstrated: (i) the isolation of a multi metal resistant S. maltophilia strain with a high Hg tolerance capacity that would be a suitable candidate for future bioremediation efforts in the polluted areas in Egypt; and (ii) the occurrence of Pseudomonas otitidis as one of the MRB.