@article {517,
	title = {A putative multicopper protein secreted by an atypical type II secretion system involved in the reduction of insoluble electron acceptors in Geobacter sulfurreducens.},
	journal = {Microbiology},
	volume = {152},
	year = {2006},
	month = {2006 Aug},
	pages = {2257-64},
	abstract = {Extracellular electron transfer onto Fe(III) oxides in Geobacter sulfurreducens is considered to require proteins that must be exported to the outer surface of the cell. In order to investigate this, the putative gene for OxpG, the pseudopilin involved in a type II general secretion pathway of Gram-negative bacteria, was deleted. The mutant was unable to grow with insoluble Fe(III) oxide as the electron acceptor. Growth on soluble Fe(III) was not affected. An analysis of proteins that accumulated in the periplasm of the oxpG mutant, but not in the wild-type, led to the identification of a secreted protein, OmpB. OmpB is predicted to be a multicopper protein, with highest homology to the manganese oxidase, MofA, from Leptothrix discophora. OmpB contains a potential Fe(III)-binding site and a fibronectin type III domain, suggesting a possible role for this protein in accessing Fe(III) oxides. OmpB was localized to the membrane fraction of G. sulfurreducens and in the supernatant of growing cultures, consistent with the type II secretion system exporting OmpB. A mutant in which ompB was deleted had the same phenotype as the oxpG mutant, suggesting that the failure to export OmpB was responsible for the inability of the oxpG-deficient mutant to reduce Fe(III) oxide. This is the first report that proposes a role for a multicopper oxidase-like protein in an anaerobic organism. These results further emphasize the importance of outer-membrane proteins in Fe(III) oxide reduction and suggest that outer-membrane proteins other than c-type cytochromes are required for Fe(III) oxide reduction in Geobacter species.},
	keywords = {Bacterial Outer Membrane Proteins, Electron Transport, Ferric Compounds, Fimbriae Proteins, Geobacter, Manganese Compounds, Mutation, Oxidation-Reduction, Oxides},
	issn = {1350-0872},
	doi = {10.1099/mic.0.28864-0},
	author = {Mehta, Teena and Childers, Susan E and Glaven, Richard and Lovley, Derek R and Mester, T{\"u}nde}
}
@article {535,
	title = {Extracellular electron transfer via microbial nanowires.},
	journal = {Nature},
	volume = {435},
	year = {2005},
	month = {2005 Jun 23},
	pages = {1098-101},
	abstract = {Microbes that can transfer electrons to extracellular electron acceptors, such as Fe(iii) oxides, are important in organic matter degradation and nutrient cycling in soils and sediments. Previous investigations on electron transfer to Fe(iii) have focused on the role of outer-membrane c-type cytochromes. However, some Fe(iii) reducers lack c-cytochromes. Geobacter species, which are the predominant Fe(iii) reducers in many environments, must directly contact Fe(iii) oxides to reduce them, and produce monolateral pili that were proposed, on the basis of the role of pili in other organisms, to aid in establishing contact with the Fe(iii) oxides. Here we report that a pilus-deficient mutant of Geobacter sulfurreducens could not reduce Fe(iii) oxides but could attach to them. Conducting-probe atomic force microscopy revealed that the pili were highly conductive. These results indicate that the pili of G. sulfurreducens might serve as biological nanowires, transferring electrons from the cell surface to the surface of Fe(iii) oxides. Electron transfer through pili indicates possibilities for other unique cell-surface and cell-cell interactions, and for bioengineering of novel conductive materials.},
	keywords = {Biotechnology, Electric Conductivity, Electron Transport, Ferric Compounds, Fimbriae Proteins, Fimbriae, Bacterial, Genes, Bacterial, Geobacter, Microscopy, Atomic Force, Microscopy, Electron, Transmission, Mutation, Nanostructures, Phylogeny},
	issn = {1476-4687},
	doi = {10.1038/nature03661},
	author = {Reguera, Gemma and McCarthy, Kevin D and Mehta, Teena and Nicoll, Julie S and Tuominen, Mark T and Lovley, Derek R}
}
