Amelioration of Cr (VI) into Cr (III) by Some Heavy Metal Resistant Bacterial Strains Isolated from Naran Valley

Total thirty-two strains were isolated from both water and soil samples collected from Naran Valley which is surrounded by the rugged mountains, located in the province of Khyber Pakhtunkhwa, Pakistan. Streak plate method was used to screen the bacterial strains for resistance against selected heavy metals like chromium (Cr), cobalt (Co), copper (Cu), nickel (Ni) and zinc (Zn). Resistance against multiple heavy metals was shown by all the strains, but S15 and W15 were significant as they exhibited a maximum resistance to chromium and copper (1200 µg/ml). These strains also presented multiple antibiotic (ampicillin, tetracycline, chloramphenicol, and erythromycin) resistance patterns. Bacterial strain W15 exhibited 90 % whereas, S15 exhibited 80 % chromium removal at an initial concentration of 800 µg/ml of chromate within 48 h of incubation. Inductive enzyme activity was shown by both the strains. 16S rRNA gene sequencing of strains S15 and W15 revealed the homology with Microbacterium sp. and Pseudomonas sp., respectively. These two multiple metal resistant strains can be further exploited for the remediation of metal polluted sites