Abstract
Shewanella oneidensis is the best understood model organism for the study of dissimilatory iron reduction. This review focuses on the current state of our knowledge regarding this extracellular respiratory process and highlights its physiologic, regulatory and biochemical requirements. It seems that we have widely understood how respiratory electrons can reach the cell surface and what the minimal set of electron transport proteins to the cell surface is. Nevertheless, even after decades of work in different research groups around the globe there are still several important questions that were not answered yet. In particular, the physiology of this organism, the possible evolutionary benefit of some responses to anoxic conditions, as well as the exact mechanism of electron transfer onto solid electron acceptors are yet to be addressed. The elucidation of these questions will be a great challenge for future work and important for the application of extracellular respiration in biotechnological processes.
Highlights
30 years ago in 1988 Ken Nealson and Charles Myers published a report in which they describe bacterial manganese reduction and growth with manganese as the sole electron acceptor. Their model organism was a bacterium at this point named Alteromonas putrefaciens MR-1 (Nealson and Myers, 1988)
The use of c-type cytochromes is a widespread solution to transfer electrons to the cell surface within various bacterial genera and a high number of c-type cytochrome encoding genes is characteristic for many dissimilatory metal reducers (Heidelberg et al, 2002)
S. oneidensis is a Gram-negative organism and respiratory electrons will have to pass two membranes and the periplasm in order to get into contact with the solid electron acceptor at the cell surface
Summary
Clarke and Johannes Gescher 1,4* 1Department of Applied Biology, Institute for Applied Biosciences, Karlsruhe Institute of Technology (CS), Karlsruhe, Germany.
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