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A severe reduction in the cytochrome C content of G eobacter sulfurreducens eliminates its capacity for extracellular electron transfer
Author(s) -
EstevezCanales Marta,
Kuzume Akiyoshi,
Borjas Zulema,
Füeg Michael,
Lovley Derek,
Wandlowski Thomas,
EsteveNúñez Abraham
Publication year - 2015
Publication title -
environmental microbiology reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.229
H-Index - 69
ISSN - 1758-2229
DOI - 10.1111/1758-2229.12230
Subject(s) - extracellular , electron transfer , reduction (mathematics) , chemistry , cytochrome c , microbiology and biotechnology , cytochrome , geobacter sulfurreducens , biophysics , biochemistry , biology , bacteria , mitochondrion , biofilm , genetics , enzyme , photochemistry , geometry , mathematics
Summary The ability of G eobacter species to transfer electrons outside the cell enables them to play an important role in a number of biogeochemical and bioenergy processes. Gene deletion studies have implicated periplasmic and outer‐surface c ‐type cytochromes in this extracellular electron transfer. However, even when as many as five c ‐type cytochrome genes have been deleted, some capacity for extracellular electron transfer remains. In order to evaluate the role of c ‐type cytochromes in extracellular electron transfer, G eobacter sulfurreducens was grown in a low‐iron medium that included the iron chelator ( 2 , 2 ′‐ bipyridine) to further sequester iron. Haem‐staining revealed that the cytochrome content of cells grown in this manner was 15‐fold lower than in cells exposed to a standard iron‐containing medium. The low cytochrome abundance was confirmed by in situ nanoparticle‐enhanced Raman spectroscopy ( NERS ). The cytochrome‐depleted cells reduced fumarate to succinate as well as the cytochrome‐replete cells do, but were unable to reduce Fe ( III ) citrate or to exchange electrons with a graphite electrode. These results demonstrate that c ‐type cytochromes are essential for extracellular electron transfer by G . sulfurreducens . The strategy for growing cytochrome‐depleted G . sulfurreducens will also greatly aid future physiological studies of Geobacter species and other microorganisms capable of extracellular electron transfer.