Microbial analysis of ground water, as the sole supplying water source in many areas, must be evaluated. Because the treatment of water cannot remove all pathogenic bacteria leaked from domestic wastewater, bacterial analysis of Bojnourd groundwater sources was performed. For this reason, membrane filter (MF) technique and Most Probable Number (MPN) method were used to evaluate the microbial quality of the water. Escherichia coli (E. coli) and Enteroccocus faecalis (E. faecalis) were traced as excremental indices. E. coli was detected from three out of six stations and E. faecalis was only isolated from one station. Although molecular techniques are very rapid and exact methods for detection of microbial community and can identify ‘Viable But Not Cultivable’ (VBNC) bacteria, they are unable to make a distinction between living and non-living microorganisms. By means of a standard technique, it is possible to study living and metabolically active microorganisms. Due to the detection of E.coli and E.feacalis in some stations the sanitization of groundwater must be revised to lessen the microbial population in this groundwater.

Streptokinase is one of the best known thrombolytic agents with widespread clinical use. However, its use is not risk-free due to its immunogenicity, hemorrhagic complications and relatively short half-life in circulation. Specific PEGylation of cysteine residue is a useful technique for reducing most of these complications. The aim of this study was designing and producing a cysteine containing mutant of streptokinase, to be used for specific PEGylation. Glut-amic acid 263, which is a surface amino acid in the structure of streptokinase protein, was selected for replacement with cysteine amino acid by site directed mutagenesis. The Glu263 codon was changed to cysteine codon by SOEing PCR technique. Then, the intact and mutated streptokinase genes were inserted into expression vector pET-26b (+). The co-nstructs were transformed to Escherichia.coli Rosetta (DE3) strain and the proteins were expressed by IPTG induction. The proteins were confirmed by SDS-PAGE and western blot analysis, purified by Ni-NTA agarose affinity chroma-tography under denaturing condition with urea and Sephadex G-25 column was applied to remove urea to refold the pr-oteins. This study indicated that by using aforesaid vector and host, cysteine containing mutant gene is expressed well and it will be appropriate for specific PEGylation.