Direct Involvement of Type II Secretion System in Extracellular Translocation of
            <i>Shewanella oneidensis</i>
            Outer Membrane Cytochromes MtrC and OmcA

Shi, Liang; Deng, Shuang; Marshall, M.; Wang, Zheming; Kennedy, David W.; Dohnálková, Alice; Mottaz, Heather M.; Hill, Eric A.; Gorby, Yuri A.; Beliaev, Alex; Richardson, David J.; Zachara, John M.; Fredrickson, James K.

doi:10.1128/jb.00514-08

Cited by 115 publications

(128 citation statements)

References 30 publications

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“…This secretion system in S. oneidensis was shown to be required for the proper localization of the outer membrane cytochromes, MtrC and OmcA, which are involved in electron transfer to anodes and to metal oxides [18,25]. In contrast, the nature and contribution of pilus-like structures to metal reduction and direct electron transfer in MFCs are not fully understood.…”

Section: Structural Analysis Of S Oneidensis Pil Msh and Flg Mutantsmentioning

confidence: 99%

“…In several of these bacteria, targeting of c cytochromes and proteins involved in metal reduction to the outer membrane is accomplished by the type II secretion system (T2SS). In S. oneidensis MR-1 and S. putrefaciens sp200, deficiencies in T2SS lead to loss of metal reduction and lack of surface exposure of c cytochromes [14,18]. Similarly, the G. sulfurreducens multicopper outer membrane protein OmpB is accomplished by the T2SS [19].…”

Section: Introductionmentioning

confidence: 99%

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The Role of Shewanella oneidensis MR‐1 Outer Surface Structures in Extracellular Electron Transfer

et al. 2010

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The ability of the metal reducer Shewanella oneidensis MR-1 to generate electricity in microbial fuel cells (MFCs) depends on the activity of a predicted type IV prepilin peptidase; PilD. Analysis of an S. oneidensis MR-1 pilD mutant indicated that it was deficient in pili production (Msh and type IV) and type II secretion (T2S). The requirement for T2S in metal reduction has been previously identified, but the role of pili remains largely unexplored. To define the role of type IV or Msh pili in electron transfer, mutants that lack one or both pilus biogenesis systems were generated and analyzed; a mutant that lacked flagella was also constructed and tested. All mutants were able to reduce insoluble Fe(III) and to generate current in MFCs, in contrast to the T2S mutant that is deficient in both processes. Our results show that loss of metal reduction in a PilD mutant is due to a T2S deficiency, and therefore the absence of c cytochromes from the outer surface of MR-1 cells, and not the loss of pili or flagella. Furthermore, MR-1 mutants deficient in type IV pili or flagella generated more current than the wild type, even though extracellular riboflavin levels were similar in all strains. This enhanced current generating ability is in contrast to a mutant that lacks the outer membrane c cytochromes, MtrC and OmcA. This mutant generated significantly less current than the wild type in an MFC and was unable to reduce Fe(III). These results indicated that although nanofilaments and soluble mediators may play a role in electron transfer, surface exposure of outer membrane c cytochromes was the determining factor in extracellular electron transfer in S. oneidensis MR-1.

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Section: Structural Analysis Of S Oneidensis Pil Msh and Flg Mutantsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Role of Shewanella oneidensis MR‐1 Outer Surface Structures in Extracellular Electron Transfer

et al. 2010

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“…The exposure of MtrC and the partnering outer-membrane cytochrome A (OmcA) on the cell surface is well documented (14). Microscopic imaging of cell exteriors labeled with an MtrC-specific antibody showed surface-exposed MtrC colocalized with cell-associated iron precipitates (15).…”

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confidence: 98%

Rapid electron exchange between surface-exposed bacterial cytochromes and Fe(III) minerals

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et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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The mineral-respiring bacterium Shewanella oneidensis uses a protein complex, MtrCAB, composed of two decaheme cytochromes, MtrC and MtrA, brought together inside a transmembrane porin, MtrB, to transport electrons across the outer membrane to a variety of mineral-based electron acceptors. A proteoliposome system containing a pool of internalized electron carriers was used to investigate how the topology of the MtrCAB complex relates to its ability to transport electrons across a lipid bilayer to externally located Fe(III) oxides. With MtrA facing the interior and MtrC exposed on the outer surface of the phospholipid bilayer, the established in vivo orientation, electron transfer from the interior electron carrier pool through MtrCAB to solid-phase Fe(III) oxides was demonstrated. The rates were 10 3 times higher than those reported for reduction of goethite, hematite, and lepidocrocite by S. oneidensis, and the order of the reaction rates was consistent with those observed in S. oneidensis cultures. In contrast, established rates for single turnover reactions between purified MtrC and Fe(III) oxides were 10 3 times lower. By providing a continuous flow of electrons, the proteoliposome experiments demonstrate that conduction through MtrCAB directly to Fe(III) oxides is sufficient to support in vivo, anaerobic, solid-phase iron respiration.mineral respiration | multiheme cytochromes | proteoliposome

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“…For example, alterations in outer membrane protein composition have been described for T2S mutants of V. cholerae, Aeromonas hydrophila, marine Vibrio sp. strain 60, and Shewanella oneidensis (30,32,63,64). The levels of outer membrane porins OmpU, OmpT, and OmpS are decreased in T2S mutants of V. cholerae (63,65), and likewise, disruption of T2S genes in A. hydrophila leads to diminished quantities of OmpF and OmpS (30).…”

mentioning

confidence: 99%

Cell Envelope Perturbation Induces Oxidative Stress and Changes in Iron Homeostasis inVibrio cholerae

et al. 2009

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The Vibrio cholerae type II secretion (T2S) machinery is a multiprotein complex that spans the cell envelope. When the T2S system is inactivated, cholera toxin and other exoproteins accumulate in the periplasmic compartment. Additionally, loss of secretion via the T2S system leads to a reduced growth rate, compromised outer membrane integrity, and induction of the extracytoplasmic stress factor RpoE (A. E. Sikora, S. R. Lybarger, and M. Sandkvist, J. Bacteriol. 189:8484-8495, 2007). In this study, gene expression profiling reveals that inactivation of the T2S system alters the expression of genes encoding cell envelope components and proteins involved in central metabolism, chemotaxis, motility, oxidative stress, and iron storage and acquisition. Consistent with the gene expression data, molecular and biochemical analyses indicate that the T2S mutants suffer from internal oxidative stress and increased levels of intracellular ferrous iron. By using a tolA mutant of V. cholerae that shares a similar compromised membrane phenotype but maintains a functional T2S machinery, we show that the formation of radical oxygen species, induction of oxidative stress, and changes in iron physiology are likely general responses to cell envelope damage and are not unique to T2S mutants. Finally, we demonstrate that disruption of the V. cholerae cell envelope by chemical treatment with polymyxin B similarly results in induction of the RpoE-mediated stress response, increased sensitivity to oxidants, and a change in iron metabolism. We propose that many types of extracytoplasmic stresses, caused either by genetic alterations of outer membrane constituents or by chemical or physical damage to the cell envelope, induce common signaling pathways that ultimately lead to internal oxidative stress and misregulation of iron homeostasis.Vibrio cholerae, a rod-shaped, highly motile, gram-negative bacterium, is the causative agent of the life threatening diarrheal disease cholera (59). The type II secretion (T2S) system plays an important role in the pathogenesis of V. cholerae by secreting cholera toxin (63), which is largely responsible for the symptoms of the disease (33). The T2S system is widespread and well conserved in gram-negative bacteria inhabiting a variety of ecological niches and likely contributes to environmental survival as well as to virulence (11,21). In V. cholerae, secretion via the T2S machinery is supported by a transenvelope complex of 12 Eps proteins (EpsC to EpsN) and the type 4 prepilin peptidase PilD (VcpD) (25,44,63). Transport of exoproteins by the T2S system occurs via a two-step process. The first step, which is either Sec or Tat dependent, requires recognition of the N-terminal signal peptide of the exoproteins and translocation through the inner membrane to the periplasm. Then the folded proteins engage the T2S machinery and are subsequently exported across the outer membrane to the extracellular milieu (23,29).Besides periplasmic accumulation of exoproteins, additional phenotypes of T2S mutants are reporte...

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Direct Involvement of Type II Secretion System in Extracellular Translocation of Shewanella oneidensis Outer Membrane Cytochromes MtrC and OmcA

Cited by 115 publications

References 30 publications

The Role of Shewanella oneidensis MR‐1 Outer Surface Structures in Extracellular Electron Transfer

The Role of Shewanella oneidensis MR‐1 Outer Surface Structures in Extracellular Electron Transfer

Rapid electron exchange between surface-exposed bacterial cytochromes and Fe(III) minerals

Cell Envelope Perturbation Induces Oxidative Stress and Changes in Iron Homeostasis inVibrio cholerae

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