Molecular Identification and Characterization of Heavy Metal Resistant Bacteria and Their Role in Bioremediation of Chromium

In this study two bacterial strains Bacillus thuringiensis (Cr-S1) and Bacillus pumilus (Cr-S2) were isolated on Cr+6 enriched nutrient agar plates at the concentration of 100 µg/ml. Minimum inhibitory concentration of chromium for Cr-S1 was 500 µg/ml while for Cr-S2 was 400 µg/ml. Maximum growth of Cr-S1 and Cr-S2 was noticed at 37ºC and at 8.0 and 7.0 pH, respectively. After careful phenotypic and biochemical characterization, confirmation was done by 16S rRNA gene amplification and sequencing. Partial sequencing results of 16S rDNA of Cr-S1 showed 97% homology with Bacillus thuringiensis while Cr-S2 showed 99% homology with Bacillus pumilus. Both the bacterial strains, B. thuringiensis (Cr-S1) and B. pumilus (Cr-S2) were assessed for their bioremediation potential in culture medium containing 100µg/ml of chromium showed 87.04% and 90.1% Cr+6 uptake at 37ºC within 24 hours. This research suggests use of B. thuringiensis and B. pumilus to remove elevated levels of, not only, chromium but also other heavy metals from polluted waters from industry.