Role of Heavy Metal Resistant Bacteria for Bioremediation of Polluted Environment

Abstract

Bioremediation refers to the use of microorganisms to reduce or eliminate contaminants from water and soil. In the current research, different bacterial strains were screened for their chromate and arsenate reduction potential. For the removal of arsenic, eight arsenic resistant bacterial strains AsK03, AsK04, AsK06, AsK07, AsK08, AsK09, AsK15 and AsK18 and for chromium removal, eight chromium resistant bacterial strains CrK02, CrK08, CrK12, CrK14, CrK16, CrK19, CrK20 and CrK21 were isolated and selected, respectively, from several contaminated soil and water samples taken from tanneries located in Kasur. Resistance to chromium and arsenic was shown by all the strains on nutrient agar at preliminary concentration of 500 µg ml-1 . The maximum tolerable concentration (MTC) of these isolates was also studied. It was found that for arsenic resistance, two strains AsK04 and AsK09 had highest MTC of 100 mg ml-1 , AsK18 had 75 mg ml-1 , AsK03, AsK06 and AsK15 had 50 mg ml-1 and AsK07 and AsK08 had 45 mg ml-1 of Na2HAsO4 concentration. Similarly, chromium resistant strains were also checked for their MTC against K2CrO4. Here MTC of CrK16 and CrK19 were highest (75 mg ml-1 ), CrK08 and CrK12 were 50 mg ml-1 , CrK02 and CrK20 were 25 mg ml-1 , CrK14 and CrK21 had least MTC of 7.5 mg ml-1 . Fifteen of the bacterial strains were genetically identified by sequencing of 16S rRNA gene. BLAST analysis revealed that the seven strains are homologous to genus Bacillus.