Engineering Electronic Communication
Cellular-electrical connections would enable devices to combine
specialties of the living world and the non-living technological world.
This new class of smart, self-renewing nanostructured systems has the
potential to revolutionize environmental sensing and energy harvesting
applications and to open new avenues to program cellular behavior.
Building towards this vision, the long-term objectives of the our
research are to develop understanding of the principles which govern
electron flow across living-non-living interfaces and to use those
principles to create electron transfer pathways between individual
living microbial cells and non-living electrodes. Our overall strategy
is both to explore how naturally-occurring microbes achieve electron
transfer to inorganic surfaces and to use genetic and materials surface
engineering to create new ‘domesticated’ hybrid cell-electrode systems.
C&E News Article “Building Better Bacteria.”
Mineralization of Carbonates
Microorganisms can greatly influence the kinetics and products of
carbonate mineral nucleation and growth. Thus, they provide a uniquely
scalable method to control both processes simultaneously. While
sequestration environments pose extreme conditions for survival,
microbial communities readily populate similar temperature, pressure,
acidity, and salinity regimes, e.g., petroleum reservoirs. Using state
of the art molecular approaches, we are tackling this largely
unexplored area to determine the key biomolecules and biochemical
reaction pathways that most effect precipitation so as to discover how
microbes can be manipulated to control carbonate mineralization under
Self Assembly of S-layer proteins
S (`surface')-layer proteins form crystalline lattices on the outsides
of many bacteria and archaea. These nearly ubquitous structures play a
number of crucial biological roles: they serve as structural scaffolds,
effect selective transport of ions and proteins, serve as templates for
mineralization, and protect against phagocytosis. While the lattice
structures of many S-layers are known, the dynamical mechanisms through
which they form are poorly understood. A molecular-level picture of the
assembly of the S-layer protein SbpA from Lysinibacillus sphaericus on
lipid bilayers was obtained only recently by using in situ atomic force
microscopy1. AFM images elucidated the phase transition of amorphous
precursors into the crystalline clusters composed of folded tetramers
and subsequent growth without disappearance of any crystal clusters.
Such a system demonstrates the non-classical crystallization behaviors
in the S-layer assembly. Molecular dynamic simulations of the S-layer
assembly using a coarse grain model also supported the non-classical
nucleation arising from a dense liquid precursor, and subsequent growth
of the crystal2. The long-term objectives of our research are to
develop predictive understanding of S-layer protein nucleation and
growth, so as to advance basic knowledge of the dynamics of coupled
nanoscale phase separation and self-assembly and to enable control of
the nanoscale structures. Together with the Whitelam, DeYoreo, and
Bertozzi groups, we are using a combination of fluorescence microscopy,
atomic force microscopy, and computer modeling to reveal the mechanisms
underlying S-layer crystallization and to identify strategies for its
1. S. Chung, S.-H. Shin, C. R. Bertozzi, J. J.
DeYoreo, Proceedings of the National Academy of Sciences of the United
States of America, 2010. 107 (38) 16536-16541.
2. Whitelam, Phys Rev Lett. 2010, 20;105(8):088102.