Uncoupling Cr(VI) Reduction in Mixed-Culture Biofilm Systems: Electron-Flow Pathway Analysis
Abstract:The electron transport pathway for microbial Cr(VI) reduction was investigated using specific inhibitors of the trans-membrane enzymes in a culture of Escherichia coli ATCC 33456 grown in a coculture with the phenol degrader, Pseudomonas putida DMP-1. The analysis involved blocking the electron flow pathway through the inner cell membrane at specific enzyme locations using known metabolic inhibitors such as azide (N3 -) and 21-oligomycin A. Cr(VI) reduction resulted from the utilization of NADH as an intermediate electron donor. Therefore, the electron pathway through NADH-dehydrogenase and cytochrome system was targeted. Results showed that 2,4-DNP restored Cr(VI) reduction activity in a culture previously inactivated by 21 oligomycin A. However, Cr(VI) reduction under uncoupler could not be sustained for a long period probably due to cell death as a result of lack of maintenance. This research contributes a new understanding of the biochemistry of Cr(VI) reduction in living cells and a more accurate representation of Cr(VI) reduction for future kinetic modeling.
Document Type: Research Article
Publication date: January 1, 2006
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