Thrust 3,4: Molecular Forces in Bacterial Adhesion at the Oxide-Water Interface
EMSL Project ID
13092
Abstract
1) Influence of Fe(III) Oxide Particle Size on Organism/Oxide Interfacial Contact Area and Electron Transfer Rates.Dr. Hochella’s research group will investigate how the surface properties of synthetic hematite nanoparticles influence the electron transfer rate from Shewanella oneidensis MR-1 under anaerobic conditions. Two or three discrete particle sizes of hematite nanoparticles will be synthesized and characterized by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and Fourier transform infra-red spectroscopy (FTIR). Included in this series will be nanoparticulate hematite synthesized by the Stanford group for use in ATR-FTIR studies of cytochrome surface interactions. The morphology and surface features of the particles, as well as their surface area, will be measured by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), tapping mode atomic force microscopy (AFM), and other techniques.
Electron transfer rates will be measured from MR-1 to the hematite surfaces as a function of hematite particle size. Careful attention will be given to cellular metabolic state, culture conditions, agitation and stirring, and hematite/organism concentration ratios. Organism/oxide incubation conditions will need to be standardized among BGC researchers to allow comparisons of results between research teams at different locations. Rigorous techniques to determine the interfacial contact area between organisms and the mineral surfaces will need to be developed. The causes for any significant differences in reduction rates between different sized materials will then be investigated using surface sensitive measurements by RAMAN, FTIR, and other techniques, and explored by varying organism/oxide concentration ratios and other experimental parameters. Electron transfer rates will also be measured for purified cytochromes if appropriate model systems (e.g., cytochromes embedded in membrane fragments or liposomes) can be developed by PNNL. Reduction rates will be normalized to interfacial contact area to determine whether an increase in rate for smaller particles (as hypothesized) is due to surface defects and irregularities, or other effects (e.g., quantum confinement phenomenon).
2) Biological Force Microscopy.
Dr. Hochella’s research group will use Biological Force Microscopy (BFM) to measure interfacial forces between Fe(III) oxides and Fe(III) oxide reduction-deficient mutants of Shewanella oneidensis MR-1. Various mutants (minus mtrB, mtrC, mtrA, and omcA) that have already been produced and phenotypically characterized by Beliaev and other members of the BGC group will be used to make mutant-Biologically Activated Force Probes (BAFPs) in collaboration with Brian Lower at PNNL. These probes will then be used to measure interfacial forces of adhesion and/or repulsion between the MR-1 mutant and various hematite forms being studied by the BGC team [MBE-grown hematite c and r cut surfaces, defected synthetic c-cut surfaces (20 um tabular hematite), the c-cut of natural hematite (specular), and others] as a function of distance between the two. Attention will be paid to the culture conditions and physiologic/metabolic status of the organism as these may have significant impact on the force curve results.
Previous applications of BFM to the Shewanella system will be extended here by i.) incorporating a more rigorous conceptual model of the MR-1 outer membrane surface (e.g., protein composition and topography) to force curve interpretation ii.) collaborating with PNNL-BGC team members (Rosso, Lower, Liang, Lu, and others) to develop modeling approaches beyond the worm-like chain model, and iii.) using MR-1 that has been carefully cultured to defined metabolic states (as used for other BGC activities and coordinated by Gorby) for force curve measurement. These investigations will strive to determine whether i.) outer membrane cytochromes, or other proteins or surface features, mediate bacterial attachment to mineral surfaces, and ii.) specific heme groups mediate direct electron transfer to Fe (III) oxides.
Project Details
Project type
Grand Challenge
Start Date
2005-01-21
End Date
2007-06-01
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Bose S., Hochella M.F., Jr., Lower B.H., Gorby Y.A., Kennedy D.W., McCready D.E., and Madden A.S. (2008) Bioreduction of hematite nanoparticles by Shewanella oneidensis MR-1. Geochimica et Cosmochimica Acta (in revision).
Bose S., Hochella M.F., Jr., Lower B.H., Gorby Y.A., Kennedy D.W., McCready D.E., and Madden A.S. (2009) Bioreduction of hematite nanoparticles by Shewanella oneidensis MR-1. Geochimica et Cosmochimica Acta, 73 (4), 962-976.
Wigginton N.S., Rosso K.M., and Hochella M.F. Jr., in revision, Mechanisms of interfacial electron transfer in bacterial decaheme cytochromes. J. Phys. Chem.
Wigginton N.S., Rosso K.M., Lower B.H., Shi L., and Hochella M.F. Jr., 2007, Electron tunneling properties of outer-membrane decaheme cytochromes from Shewanella oneidensis. Geochim. Cosmochim. Acta, 71 (3), 543-555.