Electron exchange between microbes and minerals - PowerPoint PPT Presentation

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Electron exchange between microbes and minerals

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  1. Electron exchange between microbes and minerals Gaye White, Tom Clarke, Julea Butt, David Richardson Jim Fredrickson, John Zachara, Liang Shi, Zhi Shi Marcus Edwards, Matthew Lawes A liposome model to demonstrate electron exchange between metal-reducing bacteria and Fe(III) oxides

  2. Shewanellaoneidensis • Shewanellalive just below oxic /anoxic interface • In absence of O2, can respire using a variety of terminal electron acceptors • Member of family known as DMRB(Dissimilatory Metal-Reducing Bacteria)

  3. DMRB use external electron acceptors to respire in the absence oxygen FeIIIFeII e- ? Outer membrane Periplasm H2O O2 Inner membrane e- e- Glucose CO2 Anaerobic Respiration in Dissimilatory Metal-Reducing Bacteria Aerobic Respiration

  4. How electrons cross outer membrane to reduce external electron acceptors FeIIIFeII e- OmcA MtrC MtrCAB 2 MultihemeCytochromes inside Membrane-Porin Outer membrane MtrB MtrA STC Periplasm e- 2H+ HCOOHCO2+H+ CymA (Image from Shewanella.wordpress.com) MQ MQH2 MQH2 MQ Inner membrane Fdh 2H+

  5. Liposome model to study MtrCAB acting as a wire through membrane to mineral FeIIIFeII MtrB MtrC MtrA e-

  6. Methyl viologen trapped inside liposomes to act as a redox dye 0.2 – 0.5μm diameter Methyl Viologen (MV)

  7. Reduction ofMV trapped inside proteoliposomes requires MtrCAB FeIIIFeII Reduction with dithionite e- MtrCAB MtrC B A MV MtrAB MtrC Blank

  8. Electrons accumulated inside liposomes transported out to minerals via MtrCAB No mineral added Results for MtrCABProteoliposomes White et al. PNAS 2013 Previously reported rates: Production of Fe(II) by whole cells = 5 (e s-1 protein-1) Ross et al. AEM 2009

  9. How redox potentials affect MtrCAB mediated electron transport Lipid Bilayer Na Dithionite -660 Inside liposome Outside Liposome MV2+ / MV∙+ -450 STC -140 to -250 MtrCAB 0 to -450 -160 GT/Fe2+ -120 HEM/Fe2+ -100 LEP/Fe2+ FeIII citrate +350 E0 (mV at pH7)

  10. Modelling how charge can build up and be released from the periplasm in Shewanella FeIII oxides -100 to -160 Ferric citrate +370 Dithionite -660 mV Outer membrane MtrCAB 0 to -450 STC -140 to -250 Methyl viologen -450 Periplasm -110 to -265 CymA MQ MQH2 Inner membrane -80 NAD+/NADH -330

  11. Modelling how charge can build up and be released from the periplasm in Shewanella e- e- e- e- e- Organic carbon, H2 CO2 + H2O Shewanellacan control how charge is released in response to environmental conditions

  12. Acknowledgments Jim Fredrickson John Zachara Liang Shi, Zhi Shi Kevin Rosso, Matt Marshall Alice Dohnalkova David Richardson Tom Clarke Julea Butt Marcus Edwards Matthew Lawes Daniel Bond Geoff Gralnick Ken Nealson Akihiro Okamoto