Isolation and molecular identification of mercury resistant bacteria and detection of Escherichia coli mercuric reductase gene from wastewater of Khowr-e-Musa, Iran

Abstract

Mercuric compounds are extending over large natural environment as a result of industrial pollution. Resistance to these compounds have been found in a wide range of bacterial species isolated from various environment. The aim of this study was to investigate of mercury resistant bacteria on the seashore wastewater of Khowr-e-Musa in Mahshahr area, in the south west of Iran, which one of the most important petrochemical chlor-alkali unit is located there. For this purpose, water samples were taken from wastewater of three stations. Amount of total mercury in the samples was measured using cold vapor atomic absorption spectrophotometery. Two approaches namely, conventional biochemical test and modern molecular approaches were used for identification. Mercury toxicity was measured via minimal inhibitory concentration method. Bacillus cereus, E.coli and Staphylococcus aureus were isolated and identified based on 16S rRNA gene homology, and resistance to mercuric chloride was at 400, 450 and 75 ppm, respectively. The location of E.coli mer operon was determined by plasmid curing. E.coli showed the presence of a plasmid DNA which is carries mer operon, and 1695 bp of merA gene was amplified by PCR method. The results exhibited that isolated bacteria in present study were resistant and could grow on high concentration of mercury. * Corresponding Author: Farshid Kafilzadeh  kafilzadeh@jia.ac.ir