Miniworkshop on the Abiotic/Biotic Interface

Bldg 66, Room 316, Lawrence Berkeley Lab

9am – 1pm, Friday, February 19, 2016

This miniworkshop seeks to answer the question: How can we unravel the structure, energetics, and dynamics of the nanoscale interface between inorganic materials and bacterial cells so as to enable design of efficient, scalable biohybrids?

Summary

Biohybrid technologies – combining bacterial and inorganic catalysts – have been touted as a means of converting the dilute and heterogeneous chemical energy contained in wastewater to fuels and chemicals or, conversely, as means of efficiently converting light energy into energy dense fuel. Despite recent leaps forward, biohybrids need several major breakthroughs to become viable (in particular sufficiently scalable for having a practical impact), largely because of limitations at the abiotic/biotic interface. At this interface, the challenge is to couple bacterial and inorganic catalysis on the shortest possible length scale – the nanometer scale – to optimize electronic coupling, minimize resistive losses, and avoid unwanted side reactions while simultaneously separating the incompatible environments of bacterial cells and synthetic catalysts. Addressing this task requires methods for unraveling detailed mechanisms of charge transport across bacterial cell-inorganic interfaces, which is the topic of this miniworkshop. Whether the target is bacterial catabolism powering the synthesis of everyday chemicals using inorganic catalysts, or inorganic photocatalysts powering the synthesis of complex chemicals in bacteria, knowledge of the energetics and kinetics of molecularly controlled charge transport from the inside of the organism to the inorganic catalytic site is essential for guiding biohybrid designs.

Questions to be Addressed

1. What spectroscopic/imaging tools do we have for monitoring electron transport across bacterial cell walls? Is there a need for developing methods that are currently not available?
2. What methods are available, or need to be developed, for triggering chemical processes in organisms for evaluating kinetics, e.g. triggering exoelectrogenic bacteria for generating reducing electrons to power inorganic catalysts for synthesizing useful chemicals? What are the relevant time scales for processes we need to learn about?
3. What methods are available for evaluating the energetics of the intermediates of charge transport pathways?
4. Are separate studies on subsystems, e.g. model membranes with electron transfer proteins, needed as intermediate steps towards addressing complete systems? If so, what are they?
5. Are there theoretical and modeling/simulation tools that might accelerate progress?
6. How can we use synthesis to optimize the abiotic/biotic interface? For example, what chemical linkages enable molecularly defined charge transport across bacterial-abiotic interface? What 3D nanostructured architectures of biohybrid assemblies are most effective for high product yields per geometrical area?

Relevant Literature

Reviews

B. E. Logan and K. Rabaey. Conversion of wastes into bioelectricity and chemicals by using microbial electrochemical technologies. Science 2012, 337 686-690.
An excellent review discussing key challenges to scalable biohybrid technologies for energy and chemical production.

C. M. Ajo-Franklin and A. Noy. Crossing Over: Nanostructures that Move Electrons and Ions across Cellular Membranes. Advanced Materials 2015, 27, 5797-5804.
An very recent minireview describing different classes of nanostructures used for charge transport across cell membranes.

Examples of Biohybrid Technologies

N. P. Nevin, T. L. Woodard, A. E. Franks, Z. M. Summers, D. R. Lovley. Microbial electrosynthesis: feeding microbes electricity to convert carbon dioxide and water to multicarbon extracellular organic compounds. mBio 2010, 1, e103-10.

D. E. Ross, J. M. Flynn, D. B. Baron, J. A. Gralnick, D. R. Bond Towards Electrosynthesis in Shewanella: Energetics of Reversing the Mtr Pathway for Reductive Metabolism. PLos One 2011, 6, 16649.

R. D. Cusick, Y. Kim, B. E. Logan. Energy capture from thermolytic solutions in microbial reverse-electrodialysis cells. Science 2012, 335, 1474-1477.

M. A. TerAvest, T. J. Zajdel, and C. M. Ajo-Franklin. The Mtr pathway of Shewanella oneidensis MR-1 couples substrate utilization to current production in Escherichia coli. ChemElectroChem 2014, 1, 1874-1879.

J. P. Torella, C. J. Gagliardib, J. S. Chena, D. K. Bediakob, B. Colóna, J. C. Way, P. A. Silver, and D. G. Nocera.Efficient solar-to-fuels production from a hybrid microbial-water-splitting catalyst system. Proc. Natl. Acad. Sci. U.S.A. 2015, 112, 2337–42.

C. Liu, J. J. Gallagher, K. K. Sakimoto, E. M. Nichols, C. J. Chang, M. C. Y. Chang, and P. Yang. Nanowire−Bacteria Hybrids for Unassisted Solar Carbon Dioxide Fixation to Value-Added Chemicals. NanoLett 2015, 15, 3634–3639.

K. K. Sakimoto, A. Wong, P. Yang. Self-photosensitization of nonphotosynthetic bacteria for solar-to-chemical production. Science 2016, 351,74-77.

Nanoscale Membranes for Separation of Incompatible Environments

H. S. Soo, A. Agiral, A. Bachmeier, and H. Frei. Visible Light-Induced Hole Injection into Rectifying Molecular Wires Anchored on Co3O4 and SiO2 Nanoparticles. J. Am. Chem. Soc. 2012, 134, 17104-17116.

A. Agiral, H.S. Soo, and H. Frei. Visible Light Induced Hole Transport from Sensitizer to Co3O4 Water Oxidation Catalyst across Nanoscale Silica Barrier with Embedded Molecular Wires. Chem. Mater. 2013, 25, 2264-2273.

G. Yuan, A. Agiral, N. Pellet, W. Kim, and H. Frei. Inorganic Core-Shell Assemblies for Closing the Photosynthetic Cycle. Faraday Discuss. 2014, 176, 233-249.

E. Edri and H. Frei. Charge Transport through Organic Molecular Wires Embedded in Ultrathin Insulating Inorganic Layer. J. Phys. Chem. C 119, 28326 (2015).

Structure, Dynamics, & Energetics of Complexes for Abiotic/Biotic Electron Transfer

D. J. Richardson, J. N. Butt, J. K. Fredrickson, J. M. Zachara, L. Shi, M. J. Edwards, G. White and T. A. Clarke. The ‘porin–cytochrome’model for microbe‐to‐mineral electron transfer. Molecular Microbiology 2012, 85, 201-212.
Highlights current structural understanding of protein complexes that accomplish electron transfer to metal oxides.

G. F. White, et al. “Rapid electron exchange between surface-exposed bacterial cytochromes and Fe(III) minerals.” Proc. Natl. Acad. Sci. U.S.A. 2013, 110, 6346-6351.

M. Breur, K. Rosso, J. Blumberger. “Electron flow in multiheme bacterial cytochromes is a balancing act between heme electronic interaction and redox potentials.” Proc. Natl. Acad. Sci. U.S.A.2014, 111, 611-616.