An investigation on heavy metal tolerance and antibiotic resistance properties of bacterial strain Bacillus sp. isolated from municipal waste

Abstract

The objective of our present study was to isolate heavy metal tolerant and antibiotic resistant microorganisms, the site selected being the K.M.C.’s Waste Dumping Yard, Dhapa, Kolkata, West Bengal, India, based on the extent of pollutants being discharged and the land waterways being polluted by the effluents and waste being dumped by the household and numerous industrial units. The isolated strain showed amylase & protease positive, spore forming, Grampositive bacilli and exhibited growth in wide range of substrates, temperature (30°C-40°C) & pH (6.0-11.0). Based on the 16S rDNA molecular technique, it was found that the isolate was Bacillus sp. and has a mega plasmid. Moreover it was found to grow in presence of a wide range of metals namely nickel, cadmium, chromium and cobalt in the order Cd2+> Cr6+> Ni2+> Co2+. And also it was observed that the isolate was resistant to a wide range of antibiotics namely Kanamycin (30μg/disc), Ampicillin (25μg/disc) and Methicillin (5μg/disc). Plasmid curing result showed the loss of antibiotic and heavy metal resistance profile in the isolated strain and confirms a relationship between antibiotic and heavy metal resistance with plasmid. Heavy metal tolerance test showed maximum microbial tolerance to cadmium and minimum tolerance to cobalt. This heavy metal resistant organism could be a potential agent for bioremediation of heavy metals polluted environment. Keywords: Bacillus sp, heavy metals, MTC, antibiotic resistance, plasmid curing, 16S rDNA gene sequencing.