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| Titel |
Biochemical Mechanisms Controlling Terminal Electron Transfer in Geobacter sulfurreducens |
| VerfasserIn |
R. Helmus, L. J. Liermann, S. L. Brantley, M. Tien |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250029533
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| Zusammenfassung |
| The ability of Geobacter sulfurreducens to use a variety of metals as terminal electron
acceptors (TEAs) for cellular respiration makes it attractive for use in bioremediation and
implies its importance to mineral cycling in the environment. This study is aimed at
understanding the biochemical mechanisms that allow Geobacter sulfurreducens to use
soluble and insoluble iron and manganese forms as TEAs for cellular respiration and is the
first of its kind to address the kinetics of manganese use as a TEA by G. sulfurreducens. First,
G. sulfurreducens was conditioned to grow on various soluble and insoluble iron and
manganese forms. G. sulfurreducens demonstrated enhanced growth rates when cultured
using soluble TEAs compared with insoluble TEAs. However, the lower growth rate on
insoluble iron compared with soluble iron was observed concomitantly with a 1-2
log lower cell density in stationary phase in insoluble iron cultures and a lower
growth yield per electron donor used in log growth phase. Furthermore, the growth
yield per electron was similar with both soluble and insoluble iron. These results
suggest that the net amount of energy available for biomass production achieved from
reducing insoluble iron is lower than with soluble iron, which may be due to a different
biochemical mechanism catalyzing the electron transfer to TEA dependent upon the
solubility of the TEA. One scenario consistent with this notion is that protein(s)
in the outer membrane of G. sulfurreducens that transfers electrons to insoluble
TEAs does so in a manner that uncouples electron flow from the proton pump in the
cellular membrane, similar to what we have observed with Shewanella oneidensis
MR-1.
Both the growth rate and growth yield of G. sulfurreducens on insoluble manganese were
higher than on insoluble iron, indicating that there is a difference in the flow of electrons to
the TEA in these two situations. While the different redox potentials of these elements may
affect these values, it is also possible that differential protein expression occurs when G.
sulfurreducens is grown with insoluble iron versus insoluble iron. These initial
results indicate that G. sulfurreducens allocates energy to unique cellular functions
depending on the type of TEA used, suggesting that novel mechanisms are used to
enable use of various metal forms for respiration. Follow-up protein expression
studies were then conducted and are now being used to begin to delineate what
biochemical mechanisms and cellular pathways are involved in these processes. |
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