Journal of Microbiology

Reduction of hexavalent chromium by pseudomonas aeruginosa HP014: Oh, Young Sook , choi, Sung Chan; J. Microbiol. 1997;35(1):25-29.

Abstract: Microbial reduction of hexavalent (VI) to trivalent (III) chromium decreases its toxicity by two orders of magnitude. In order to investigate the nature of Cr-reduction, Cr-resistant Pseudomonas aeruginosa HP014 was isolated and tested for its reduction capability. At the concentration of 0.5 mM Cr(VI), cell growth was not inhibited by the presence of Cr(VI) in a liquid medium, and Cr(VI) reduction was accompanied by ell growth. When cell-free extract was tested, the reduction of Cr(VI) showed a saturation kinetics with the maximum specific activity of 0.33 umol min^-1 mg^-1 cell protein, and an apparent K. of 1.73 mM Cr(VI). The activity required either NADH or NADPH as an electron donor. However, NADPH gave 50% as much activity as NADH. To locate the reductase activity, cell free extract was centrifuged at 150,000×g, and subsequently the supernatant and pelleted membrane fractions were tested for Cr(VI) reduction activity. The supernatant of the centrifugation showed almost the same Cr(VI) reduction activity as compared with that of the cell-free extract, indicating that the Cr(VI)-reducing activity of P. aeruginosa HP-14 is due to soluble enzyme. Moreover, the activity appeared to be the highest among the known activities, suggesting that the strain might be useful for remediation of Cr(VI)-contaminated sites.

Bacterial Color Response to Hexavalent Chromium, Cr^6+: Ka Hong Cheung , Ji-Dong Gu; J. Microbiol. 2002;40(3):234-236.

Abstract: A blue pigment-producing bacterium, Vogesella indigofera, was isolated and quantified for the relationship between its synthesis of a blue pigment and exposure concentrations of Cr^6+ . The concentration of Cr^6+ and the percentage of blue colonies on agar plates was negatively correlated (r^2 = -0.8683). Critical concentrations inhibiting bacterial pigment production were found to be between 100-150 ug Cr^6+ /ml on agar plates and 200-300 ug Cr^6+ /ml in liquid culture. As the blue color is characteristic and easily observable, the bacterium Vogesella indigofera may have potential applications in the detection and monitoring of environmental pollution.

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