Biologia 67/5: 827—836, 2012 Section Cellular Molecular Biology DOI: 10.2478/s11756-012-0099-5 Isolation and characterization of heavy metal tolerant Gram-positive bacteria with bioremedial properties from municipal waste rich soil of Kestopur canal (Kolkata), West Bengal, India Kamala Gupta 1 *, Chitrita Chatterjee 2 & Bhaskar Gupta 2 * 1 Department of Botany, Bethune College, 181-Bidhan Sarani, West Bengal, Kolkata, India; e-mail: kamalagupta@gmail.com 2 Department of Biotechnology, Molecular Biology Laboratory, Presidency University, 86/1 College Street, West Bengal, Kolkata, India; e-mail: bhaskarzoology@gmail.com Abstract: The present study was conducted to determine the culturable bacterial profile from Kestopur canal (Kolkata, India) and analyze their heavy metal tolerance. In addition to daily sewage including solid and soluble wastes, a considerable load of toxic metals are released into this water body from industries, tanneries and agriculture, household as well as health sectors. Screening out microbes from such an environment was done keeping in mind their multifunctional application especially for bioremediation. Heavy metals are major environmental pollutants when present in high concentration in soil and show potential toxic effects on growth and development in plants and animals. Some edible herbs growing in the canal vicinity, and consumed by people, were found to harbour these heavy metals at sub-toxic levels. The bioconcentration factor of these plants being <1 indicates that they probably only absorb but not accumulate heavy metals. All the thirteen Gram- positive bacteria isolated from these plants rhizosphere were found to tolerate high concentration of heavy metals like Co, Ni, Pb, Cr, Fe. Phylogenetic analysis of their 16S rDNA genes revealed that they belonged to one main taxonomic group – the Firmicutes. Seven of them were found to be novel with 92–95% sequence homology with known bacterial strains. Further microbiological analyses show that the alkaliphilic Bacillus weihenstephanensis strain IA1 and Exiguobacterium aestuarii strain CE1, with selective antibiotic sensitivity along with high Ni 2+ and Cr 6+ removal capabilities, respectively, can be prospective candidates for bioremediation. Key words: antibiotic resistance; biochemical assay; growth curve; heavy metal tolerance; pH tolerance; 16S rDNA. Abbreviations: BCF, bioconcentration factor; LB, Luria Bertani; MIC, minimum inhibitory concentration. Introduction Heavy metals such as lead (Pb), chromium (Cr), cad- mium (Cd), mercury (Hg), iron (Fe), cobalt (Co) and nickel (Ni) are important environmental pollutants, particularly in areas with high anthropogenic pressure. Their presence in atmosphere, soil and water, even in traces, can cause serious problem to all organisms (Is- lam et al. 2007). Heavy metal contamination of the food items is one of the most important aspects of food qual- ity assurance (Wang et al. 2005; Khan et al. 2008). International and national regulations on food quality have lowered the maximum permissible levels of toxic metals in food items due to an increased awareness of the risk, these metals pose to food chain contam- ination. Rapid and unorganized industrialization and urbanization have contributed to the elevated level of heavy metals in the urban environment of the devel- oping countries, such as China (Wong et al. 2003) and India (Khillare et al. 2004; Sharma et al. 2008). Heavy metals and their derivatives are non-bio- degradable and persistent environmental contaminants which may be deposited on the surfaces and then ad- sorbed into the tissues of the vegetables. Vegetables constitute an important part of the human diet since they contain carbohydrates, proteins, vitamins, miner- als and fibres required for human health. They also act as neutralizing agents for acidic substances formed dur- ing digestion. Plants take up heavy metals by absorbing them from deposits on the parts of the plants exposed to the air from polluted environment as well as from contaminated soils (Khairiah et al. 2004; Al-Jassir et al. 2005; Sharma et al. 2008). In many developing coun- tries it is a common practice to grow vegetables along banks of rivers passing through urban centres. Waters of such rivers have often been reported to be polluted by heavy metals (Mashauri & Mayo 1990; Kashem & Singh 1999; Othman 2001). The extent of absorption of the elements by the plant depends on, among other things, the nature of the plant, chemical constitution of the pol- * Corresponding author c 2012 Institute of Molecular Biology, Slovak Academy of Sciences