TAILIEUCHUNG - Reduction of chromium(VI) by locally isolated Pseudomonas sp. C-171
A strain of Pseudomonas sp. C-171 capable of tolerating hexavalent chromium (Cr+6) up to 2000 ppm as potassium dichromate was isolated from domestic sewage. The Cr+6 reduction was checked by growing the isolated strain in a medium containing potassium dichromate as Cr+6 source. | Turk J Biol 31 (2007) 161-166 © TÜB‹TAK Reduction of Chromium(VI) by Locally Isolated Pseudomonas sp. C-171 1 2 1 Mujeeb UR RAHMAN , Shereen GUL , Mohammad Zahoor UL HAQ 1 PCSIR Laboratories, . Box 387, Mastung Road, Quetta, Balochistan, PAKISTAN 2 Department of Botany, Government Girls College, Quetta, Balochistan, PAKISTAN Received: +6 Abstract: A strain of Pseudomonas sp. C-171 capable of tolerating hexavalent chromium (Cr ) up to 2000 ppm as potassium dichromate was isolated from domestic sewage. The Cr+6 reduction was checked by growing the isolated strain in a medium containing potassium dichromate as Cr+6 source. The rate of growth of Pseudomonas sp. C-171 decreased with the increase in Cr+6 concentration of the medium. The maximum rate of chromium reduction was observed during the log phase of bacterium growth. The reduction of hexavalent chromium was inoculum concentration dependent. The accumulation of chromium hydroxide around the bacterial cells and slight elongation of cells were observed. Key Words: Hexavalent chromium, reduction, Pseudomonas sp. C-171, accumulation, chromium hydroxide, cell elongation Introduction +6 Hexavalent chromium (Cr ) is a common water pollutant and is toxic to most organisms. Cr+6 is highly soluble in water and forms divalent species, chromate (CrO4-2) and dichromate (Cr2O7-2). Cr+6 is a strong oxidizing agent. As a result of redox reactions, Cr+6 is reduced to trivalent chromium Cr+3, which forms insoluble chromium hydroxide at neutral pH. In biological systems, the cellular membranes are permeable to Cr+6. Cr+6 passes through the cellular membrane and is reduced to Cr+3 in mitochondria and nuclei, as well as in cytoplasm. Although Cr+3 is impermeable to the membrane, Cr+3 generated inside the cell binds stably to protein and interacts with nucleic acid (1). Microbial transformations for different metallic minerals have been reported by Chiong et al. (2) and Lebedeva and Lyalikova (3). The .
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