Pak. J. Chem. 7(1-4): 12-16, 2017 Full Paper ISSN (Print): 2220-2625 ISSN (Online): 2222-307X DOI: 10.15228/2017.v07.i01-4.p03 *Corresponding Author Received 01 th April 2017, Accepted 15 th June 2017 Heavy Metal Resistant Bacteria: A Potential Candidate for Bioremediation Shafaq Aiyaz Hassan a *, Erum Hanif a , Areeba Siddiqui a , Ehtisham Asif a , Umme Hani Khan a , Asad Khan Tanoli b a Department of Biotechnology, University of Karachi, 75270, Karachi. b Department of Chemistry, University of Karachi, 75270, Karachi. *email of corresponding author: shafaqah@uok.edu.pk ABSTRACT: Microorganisms have numerous biotechnological applications for bioremediation of metal-contaminated soil and water systems. In view of this, the present study was aimed to evaluate the abilities of microorganisms for tolerance and biosorption of heavy metals. In this study we have isolated 30 different bacterial strains from soil. Morphological and biochemical characterization was carried out. It was shown that Pseudomonas sp. was most common isolate among heavy metal resistant organisms that are capable of resisting 5 heavy metals (Ni, Pb, Cr, Cu and Cd) of concentration range 50-300μg/ml. Among 30 isolates, 4 of them showed high degree of resistance against all metals at concentration at 300μg/ml. Bacterial strains isolated in this study can be used in bioremediation and bio-mining. Keywords: Metal Resistance, Bioremediation, Maximum Tolerance Concentration MTC. 1. INTRODUCTION Heavy metals have adversed affect on the environment and living organisms [1]. Industrial effluents containing heavy metals are reported to pose health hazards to plants, animals and humans [2]. The commonly encountered heavy metals in environment include a numerous metal ions like arsenic, cadmium, chromium, copper, lead, nickel and zinc are of immense threat for overall environment [3]. Heavy metals may enter the environment by man-made activities. Soil erosion, mining, industrial effluents, urban runoff, sewage discharge are among potential sources of these contaminants [4]. Heavy metals are known to have their affect on cell organelles like cell membrane, mitochondrial, lysosome, endoplasmic reticulum, involved in metabolism, detoxification, damage repair in biological systems. Metal ions interact with DNA and nuclear proteins, causing DNA damage and cause conformational changes that may lead to cell cycle modulation, carcinogenesis or apoptosis [5]. Detoxification of contaminated site with the help of microorganism has evolved as the most effective tool to combat the problem of pollution. Microorganisms are being exploited for their ability to remediate the toxic pollutants released in the environment due to human activities and industrialization [6]. Biosorption, extracellular precipitation, accumulation of metals, oxidation-reduction and efflux of heavy metals from the cell are among the several mechanisms developed by microorganisms to resist heavy metals as reported by many researchers [7-9]. The interest in heavy metal uptake by bacteria has been increased nowadays especially because of their biotechnological potential that microorganisms have for the removal and recovery of metals [10]. Bacteria are known as good biosorbents and with the proper understanding may be in near future. They proved to be good alternatives for the removal of metal ions from the environment [10]. The present study was aimed to isolate and screened the heavy metal resistant bacterial strains from the soil that can be exploit in future for bio-mining and bioremediation. 2. MATERIALS AND METHODS: 2.1. Materials: Microbiological culture media used in this study was purchased from Oxoid ltd. All the salts reagents and chemical used in this study were purchased from Merck chemicals and were of analytical grade. 2.2. Sample Collection The soil sample was collected from road side (University road, Karachi) in ziplock bags and processed in Department of Biotechnology, University of Karachi. 2.3. Isolation of Metal Resistant Bacteria: To isolate bacteria, nutrient agar plates were prepared and supplemented with appropriate volume of metal salt solutions. For initial screening of metal resistant bacteria, the saline dilution was made and added to nutrient agar plate containing