Effects of soluble flavin on heterogeneous electron transfer between surface-exposed bacterial cytochromes and iron oxides》.pdf

Available online at ScienceDirect Geochimica et Cosmochimica Acta 163 (2015) 299–310 /locate/gca Effects of soluble flavin on heterogeneous electron transfer between surface-exposed bacterial cytochromes and iron oxides Zheming Wang a,⇑, Zhi Shi a, Liang Shi a, Gaye F. White b, David J. Richardson b, Thomas A. Clarke b, Jim K. Fredrickson a, John M. Zachara a,⇑ a Pacific Northwest National Laboratory, PO Box 999, MS K8-96, Richland, WA 99352, United States b Centre for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom Received 27 October 2014; accepted in revised form 28 March 2015; available online 6 April 2015 Abstract Dissimilatory iron-reducing bacteria can utilize insoluble Fe(Mn)-oxides as a terminal electron acceptor under anaerobic conditions. For Shewanella species specifically, evidence suggests that iron reduction is associated with the secretion of flavin mononucleotide (FMN) and riboflavin. However, the exact mechanism of flavin involvement is unclear; while some indicate that flavins mediate electron transfer (Marsili et al., 2008), others point to flavin serving as co-factors to outer membrane pro- teins (Okamoto et al., 2013). In this work, we used methyl viologen (MV+)-encapsulated, porin-cytochrome complex (MtrCAB) embedded liposomes (MELs) as a synthetic model of the Shewanella outer membrane to investigate the proposed mediating behavior of microbially produced flavins. The red