PMID:22360295

Citation	Mitchell, AC, Peterson, L, Reardon, CL, Reed, SB, Culley, DE, Romine, MR and Geesey, GG (2012) Role of outer membrane c-type cytochromes MtrC and OmcA in Shewanella oneidensis MR-1 cell production, accumulation, and detachment during respiration on hematite. Geobiology 10:355-70
Abstract	The iron-reducing bacterium Shewanella oneidensis MR-1 has the capacity to contribute to iron cycling over the long term by respiring on crystalline iron oxides such as hematite when poorly crystalline phases are depleted. The ability of outer membrane cytochromes OmcA and MtrC of MR-1 to bind to and transfer electrons to hematite has led to the suggestion that they function as terminal reductases when this mineral is used as a respiratory substrate. Differences in their redox behavior and hematite-binding properties, however, indicate that they play different roles in the electron transfer reaction. Here, we investigated how these differences in cytochrome behavior with respect to hematite affected biofilm development when the mineral served as terminal electron acceptor (TEA). Upon attachment to hematite, cells of the wild-type (WT) strain as well as those of a ΔomcA mutant but not those of a ΔmtrC mutant replicated and accumulated on the mineral surface. The results indicate that MtrC but not OmcA is required for growth when this mineral serves as TEA. While an OmcA deficiency did not impede cell replication and accumulation on hematite prior to achievement of a maximum surface cell density comparable to that established by WT cells, OmcA was required for efficient electron transfer and cell attachment to hematite once maximum surface cell density was achieved. OmcA may therefore play a role in overcoming barriers to electron transfer and cell attachment to hematite imposed by reductive dissolution of the mineral surface from cell respiration associated with achievement of high surface cell densities.
Links	PubMed Online version:10.1111/j.1472-4669.2012.00321.x
Keywords	Bacterial Outer Membrane Proteins/metabolism; Cytochrome c Group/genetics; Cytochrome c Group/metabolism; Ferric Compounds/metabolism; Gene Deletion; Oxidation-Reduction; Shewanella/genetics; Shewanella/growth & development; Shewanella/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
SHEON:Q8EG33		GO:0022904: respiratory electron transport chain	ECO:0000315:		P		Figure 1C: the surface density of cells of the (-)omcA mutant attributable to hematite-specific cell accumulation (A) decreased to 45% of Amax	complete CACAO 9169

References

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