The ‘porin–cytochrome’ model for microbe-to-mineral electron transfer

Authors

David Richardson, University of East AngliaFollow
Julea Butt, University of East Anglia
James K. Fredrickson, Pacific Northwest National LaboratoryFollow
John M. Zachara, Pacific Northwest National LaboratoryFollow
Liang Shi, Pacific Northwest National LaboratoryFollow
Marcus Edwards, University of East Anglia
Gaye White, University of East Anglia
Nanakow Baiden, University of East Anglia
Andrew Gates, University of East Anglia
Sophie Marritt, University of East Anglia
Thomas Clarke, University of East AngliaFollow

Date of this Version

2012

Citation

Molecular Microbiology (2012) 85(2), 201–212; doi:10.1111/j.1365-2958.2012.08088.x

Abstract

Many species of bacteria can couple anaerobic growth to the respiratory reduction of insoluble minerals containing Fe(III) or Mn(III/IV). It has been suggested that in Shewanella species electrons cross the outer membrane to extracellular substrates via ‘porin–cytochrome’ electron transport modules. The molecular structure of an outer-membrane extracellular-facing deca-haem terminus for such a module has recently been resolved. It is debated how, once outside the cells, electrons are transferred from outer-membrane cytochromes to insoluble electron sinks. This may occur directly or by assemblies of cytochromes, perhaps functioning as ‘nanowires’, or via electron shuttles. Here we review recent work in this field and explore whether it allows for unification of the electron transport mechanisms supporting extracellular mineral respiration in Shewanella that may extend into other genera of Gram-negative bacteria.