• Journal of Microbiology and Biotechnology
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• v.16 no.6
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• pp.855-862
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• 2006

Hexavalent chromium ($Cr^{6+}$) is a highly harmful pollutant, which can be detoxified and precipitated through reduction to $Cr^{3+}$. Bacillus megaterium TKW3 previously isolated from chromium-contaminated marine sediments was capable of reducing $Cr^{6+}$ in concomitance with metalloids ($Se^{4+}$, $Se^{6+}$, and $As^{5+}$). Notwithstanding approximately 50% inhibition, it was the first report of simultaneous bacterial reduction of $Cr^{6+}$ and $Se^{4+}$ (to elemental Se). No significant difference was observed among electron donors (glucose, maltose, and mannitol) on $Cr^{6+}$ reduction by B. megaterium TKW3. The reduction was constitutive and determined to be non-plasmid mediated. Peptide mass fingerprints (PMF) revealed a novel aerobic membrane-associated reductase with $Cr^{6+}$-induced expression and specific reductive activity (in nmol $Cr^{6+}$/mg protein/min) of 0.220 as compared with 0.087 of the soluble protein fraction. Respiratory inhibitor $NaN_3$ did not interfere with the reductase activity. Transmission electron microscopy with energy dispersive X-ray (TEM-EDX) analysis confirmed the aggregation of reduced chromium along the intracellular membrane region. Future identification of the N-terminal amino acid sequence of this reductase will facilitate purification and understanding of its enzymatic action.

• Journal of Internet Computing and Services
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• v.11 no.5
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• pp.119-126
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• 2010

In this paper, we analyze the robustness of transformed-key asymmetric watermarking system and show its improvement by proposing a new detection method. Based on the assumption that the transformed-key asymmetric watermarking system is under the threat of subtraction attack, we first propose the criterion for the detection performance of the watermarking system and analyze the optimum condition on the system. Next, a new detection method is proposed to improve the detection performance of the system based on the criterion. The proposed improvement makes the system robust to not only subtraction attack but also Wu's attack.