The 'porin-cytochrome' model for microbe-to-mineral electron transfer.
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.
Centre for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich NR47TJ, UK. d.richardson@uea.ac.uk
David J
DJ
Richardson
Julea N
JN
Butt
Jim K
JK
Fredrickson
John M
JM
Zachara
Liang
L
Shi
Marcus J
MJ
Edwards
Gaye
G
White
Nanakow
N
Baiden
Andrew J
AJ
Gates
Sophie J
SJ
Marritt
Thomas A
TA
Clarke
D000693:Anaerobiosis; D003580:Cytochromes / Q000378:metabolism*; D004579:Electron Transport; D008903:Minerals / Q000378:metabolism*; D008954:Models, Biological; D010084:Oxidation-Reduction; D018272:Porins / Q000378:metabolism*; D020592:Shewanella / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*
D003580:Cytochromes; D008903:Minerals; D018272:Porins