Role of outer membrane c-type cytochromes MtrC and OmcA in Shewanella oneidensis MR-1 cell production, accumulation, and detachment during respiration on hematite

Authors Organisations
  • Andy Mitchell(Author)
  • L. Peterson(Author)
    Montana State University
  • C. L. Reardon(Author)
    Pacific Northwest National Laboratory
  • S. B. Reed(Author)
    Pacific Northwest National Laboratory
  • D. E. Culley(Author)
    Pacific Northwest National Laboratory
  • M. R. Romine(Author)
    Pacific Northwest National Laboratory
  • Gill G. Geesey(Author)
Type Article
Original languageEnglish
Pages (from-to)355-370
JournalGeobiology
Volume10
Issue number4
Early online date23 Feb 2012
DOI
Publication statusPublished - Jul 2012
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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 DomcA mutant but not those of a DmtrC 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 fromcell respiration associated with achievement of high surface cell densities.