Abstract
Dissimilatory reduction of metal (e.g. Fe, Mn) (hydr)oxides represents a challenge for microorganisms, as their cell envelopes are impermeable to metal (hydr)oxides that are poorly soluble in water. To overcome this physical barrier, the Gram-negative bacteria Shewanella oneidensis MR-1 and Geobacter sulfurreducens have developed electron transfer (ET) strategies that require multihaem c-type cytochromes (c-Cyts). In S. oneidensis MR-1, multihaem c-Cyts CymA and MtrA are believed to transfer electrons from the inner membrane quinone/quinol pool through the periplasm to the outer membrane. The type II secretion system of S. oneidensis MR-1 has been implicated in the reduction of metal (hydr)oxides, most likely by translocating decahaem c-Cyts MtrC and OmcA across outer membrane to the surface of bacterial cells where they form a protein complex. The extracellular MtrC and OmcA can directly reduce solid metal (hydr)oxides. Likewise, outer membrane multihaem c-Cyts OmcE and OmcS of G. sulfurreducens are suggested to transfer electrons from outer membrane to type IV pili that are hypothesized to relay the electrons to solid metal (hydr)oxides. Thus, multihaem c-Cyts play critical roles in S. oneidensis MR-1- and G. sulfurreducens-mediated dissimilatory reduction of solid metal (hydr)oxides by facilitating ET across the bacterial cell envelope.
Highlights
Introduction cType cytochromes (c-Cyts) are ubiquitous in most living organisms, where they play vital roles in mediating electron transfer (ET) reactions associated with respiration
These motifs with covalently bound haems are the key components used to constitute the haem-containing domains whose diverse functions range from binding of O2 and catalysis to electron transfer and accumulation (Stevens et al, 2004; Rodrigues et al, 2006). c-type cytochromes (c-Cyts) have been extensively investigated, and several excellent reviews have been dedicated to the structures, chemistry and biogenesis of c-Cyts (Stevens et al, 2004; Mowat and Chapman, 2005)
This review focuses on the unique features of bacterial c-Cyts with multiple haems and their roles in bacteria-mediated dissimilatory reduction of solid metaloxides
Summary
Respiration of metal (hydr)oxides by Shewanella and Geobacter: a key role for multihaem c-type cytochromes. Follow this and additional works at: https://digitalcommons.unl.edu/usdoepub Part of the Bioresource and Agricultural Engineering Commons. Liang; Squier, Thomas C.; Zachara, John M.; and Fredrickson, James K., "Respiration of metal (hydr)oxides by Shewanella and Geobacter: a key role for multihaem c-type cytochromes" (2007). This Article is brought to you for free and open access by the U.S Department of Energy at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in US Department of Energy Publications by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln.
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