title: Two different electron transfer pathways may involve in azoreduction in Shewanella decolorationis S12.
abstract: 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.
authors.affiliation: South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China.
authors.forename: Xingjuan
authors.initials: X
authors.lastname: Chen
authors.forename: Meiying
authors.initials: M
authors.lastname: Xu
authors.forename: Jinbo
authors.initials: J
authors.lastname: Wei
authors.forename: Guoping
authors.initials: G
authors.lastname: Sun
mesh_terms: D001391:Azo Compounds / Q000378:metabolism*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D004396:Coloring Agents / Q000378:metabolism*; D004251:DNA Transposable Elements; D004583:Electrons; D005561:Formates / Q000378:metabolism; D017353:Gene Deletion; D053858:Metabolic Networks and Pathways; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009243:NAD / Q000378:metabolism; D010084:Oxidation-Reduction; D020592:Shewanella / Q000378:metabolism*
chemical_list: D001391:Azo Compounds; D001425:Bacterial Outer Membrane Proteins; C118373:CcmA protein, bacteria; D004396:Coloring Agents; D004251:DNA Transposable Elements; D005561:Formates; D009243:NAD; C030544:formic acid