International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 05 Issue: 08 | Aug 2018 www.irjet.net p-ISSN: 2395-0072 © 2018, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 355 Potential risks associated with bacterial strains isolated from heavy metal rich soil of a landfill area Sayantan De 1 , Shaunak Ghosh 2 1,2 Department of Biotechnology, Heritage Institute of Technology, Kolkata ----------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - Dumping of Industrial wastes in the water and landfill areas causes heavy metal contamination which is adversely affecting the environment. Among all the heavy metals Arsenic, Mercury and Nickel are among the few of most abundantly found toxic metals in contaminated areas, posing serious threat to the ecosystem. Our experimental study was based on these three metals. The result of change in the ecosystem with the increasing concentration of such toxic elements in the nature has tremendous effect on the bacterial population as well. In order to adapt with the new environment few bacterial species are developing tolerance towards high concentration of these heavy metals which may develop as new pathogens creating new form of diseases. On the other hand, they can have great utility in the process of bioremediation and waste management in future. Our aim in this project was to isolate newer strains of such bacterial species which can survive high concentration of heavy metals in the soil. We also have tested their antibiotic resistance property to evaluate the potential threat they may pose on human lives, if they prove to be pathogenic in nature. A landfill area in Jalpaiguri district, West Bengal was chosen to collect the soil sample for our experiment. Then heavy metal (Ni 2+ , Hg 2+ , and As 3+ ) tolerant bacterial colonies were isolated and further characterized both morphologically and biochemically. Key Words: Landfills, Heavy metals, Heavy metal tolerant, Antibiotic-Resistant 1. INTRODUCTION Metals whose atomic density is more than 5 g/cm 3 are defined as heavy metals [7]. Heavy metals cannot be degraded or destroyed and hence they are treated as stable, persistent contaminants of the environment [8]. Some heavy metals are essential for living but are required only in very small quantity as micro nutrients and hence are known as Dztrace elementsdz. If present in slightly higher concentration than what is needed they can cause severe harm to the living organisms. Many agricultural and industrial and even domestic practices are responsible for release of such heavy metals in the environment creating pollution of land and water [9]. Mining power stations and the application of pesticides, fertilizer in the agricultural fields and sewage sludge are few of the sources of heavy metal contamination in the soil [10]. Apart from plants and animals, microbes are also very much affected my heavy metal contaminations. Indigenous microbial populations face severe challenges due to such contaminations as these can alter microbial activities and even nitrogen fixation properties of soil bacteria. These causes damage to the cell membrane and can alter enzymes specificity thereby hampering cellular functions. Even at certain instances they can also alter or damage the structure of the DNA [11]. But having the advantage of shorter life cycle, the microbes can adapt very fast to the changing environment. Heavy metal contamination is significantly higher in sewage and dumping areas (landfills )[1]. Such landfill areas are also populated with wide varieties of unknown microorganisms. Very few works have been done to evaluate bacterial diversity of such landfill areas. Microbial populations in heavy metal polluted environments contain bacteria which have been adapted to toxic concentrations of different heavy metals like Ni, As, Hg and become metal resistant. Those microorganisms developed wide mechanisms for survival in the presence of highly toxic heavy metals, and acquired certain genetic properties [3]. They have evolved mechanism to either eliminate or detoxify such metals within their cells. Many such bacterial strains have already been isolated having the property to tolerate high concentration of heavy metals. It has been found in many experiments that many of those bacteria which are resistant to the effects of high concentrations of heavy metals in their ecosystem are often resistant to several antibiotics. In this study, our aim was to isolate several strains of bacterium from landfill damp soil and toidentify the particular strains which have the ability to tolerate different concentration of heavy metals along with evaluation of their antibiotic resistance ability. The relationship between heavy metal tolerance and antibiotic resistance properties of isolated bacteria with its plasmid content has been previously correlated in many studies. In recent years, the disposal of industrial wastes containing heavy metals,mainly in the nearby water bodies, has resulted in an increase in population of resistant bacteria. The results are indispensably more common in industrial hubs. Discharge of wastewater containing heavy metals into rivers causes accumulation in soil particles (in the form of clay) and transfer of these to far away places [12]. The results of some studies show that, in landfill areas, the concentration of heavy metals in less settable particles such as clay, can travel to distance places. Some researchers have indicated that the rate of metal (As, Ni, Hg...) exhibition concentration in West Bengal, India exceeds the quality guideline for the concentration of heavy metals in sediments. Since soil is one of the most important environments for microbes and is