Redox protein nanoscale domains on the cell surface of a bacterium, Shewanella oneidensis MR1, grown in the absence and presence of electron acceptors, is topographically characterized using combined atomic force microscopy (AFM) and confocal surface enhanced Raman scattering (SERS) spectroscopy.1 The protruding nanoscale domains on the outer membrane of S. oneidensis were observed, as was their disappearance upon exposure to electron acceptors such as oxygen, nitrate, fumarate, and iron nitrilotriacetate (FeNTA). Our experimental results from our AFM imaging and SERS spectroscopy, consistent with the literature, suggest the protruding nanoscale surface domains as heme-containing secretions. We have further investigated single-cell reduction of toxic Cr(VI) by the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1 (MR-1), an important bioremediation process.2 Our experiments indicate that the toxic and highly soluble Cr(VI) can be efficiently reduced to the less toxic and non-soluble Cr2O3 nanoparticles by MR-1. Co-localization of Cr2O3 and cytochromes by EDX imaging and Raman spectroscopy suggests a terminal reductase role for MR-1 surface-exposed cytochromes MtrC and OmcA. Our results on the distributions of redox proteins on microbial cell surfaces will be helpful for a mechanistic understanding of the behaviors of surface proteins and their interactions with redox environments.  References:  1. V. Biju, D. Pan, Yuri A. Gorby, Jim Fredrickson, J. Mclean, D. Saffarini and H. Peter Lu, 'Correlated Spectroscopic and Topographic Characterization of Nanoscale Domains and Their Distributions of a Redox Protein on Bacterial Cell Surfaces,' Langmuir 23  , 1333-1338 (2007).  2. Yuanmin Wang, Papatya Sevinc, Sara Balchik, Jim Fridrickson, Liang Shi, H. Peter Lu, �Single-Cell Imaging and Spectroscopic Analyses of Cr(VI) Reduction on the Surface of Bacterial Cells,� Langmuir, 29  , 950-956 (2013).

Combined spectroscopic and topographic characterization of nanoscale electron transfer reactivity and distributions of redox proteins on bacterial cell surfaces

246th National Meeting (2013)

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