Journal
APPLIED MICROBIOLOGY AND BIOTECHNOLOGY
Volume 86, Issue 2, Pages 743-751Publisher
SPRINGER
DOI: 10.1007/s00253-009-2376-y
Keywords
Electron transfer pathways; Azoreduction; ccmA; Azo dyes; Shewanella decolorationis S12
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Funding
- Chinese National Natural Science Foundation [30500009, 30670020]
- Chinese National Programs for High Technology Research and Development [2006AA06Z322]
- Natural Science Foundation Guangdong province [9351007002000001]
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Electron transfer pathways for azoreduction by S. decolorationis S12 were studied using a mutant S12-22 which had a transposon insertion in ccmA. The results imply that there are two different pathways for electron transport to azo bonds. The colony of S12-22 was whitish and incapable of producing mature c-type cytochromes whose alpha-peak was at 553 nm in the wild type S12. The mutant S12-22 could not use formate as the sole electron donor for azoreduction either in vivo or in vitro, but intact cells of S12-22 were able to reduce azo dyes of low polarity, such as methyl red, when NADH was served as the sole electron donor. Although the highly polar-sulfonated amaranth could not be reduced by intact cells of S12-22, it could be efficiently reduced by cell extracts of the mutant when NADH was provided as the sole electron donor. These results suggest that the mature c-type cytochromes are essential electron mediators for the extracellular azoreduction of intact cells, while the other pathway without the involvement of mature c-type cytochromes, NADH-dependent oxidoreductase-mediated electron transfer pathway can reduce lowly polar sulfonated azo dyes inside the whole cells or highly polar sulfonated azo dyes in the cell extracts without bacterial membrane barriers.
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