title: Combined spectroscopic and topographic characterization of nanoscale domains and their distributions of a redox protein on bacterial cell surfaces.
abstract: 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. 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). Using SERS spectroscopy, a redox heme protein was identified as a major component of the cell surface domains. This conclusion was further confirmed by the disappearance of Raman vibrational frequencies, characteristic of heme proteins, upon exposure of the cells to electron acceptors. Our experimental results from our AFM imaging and SERS spectroscopy, consistent with the literature, suggest the protruding nanoscale surface domains as heme-containing secretions. 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.
authors.affiliation: Fundamental Science Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA.
authors.forename: Vasudevanpillai
authors.initials: V
authors.lastname: Biju
authors.forename: Duohai
authors.initials: D
authors.lastname: Pan
authors.forename: Yuri A
authors.initials: YA
authors.lastname: Gorby
authors.forename: Jim
authors.initials: J
authors.lastname: Fredrickson
authors.forename: Jeff
authors.initials: J
authors.lastname: McLean
authors.forename: Daad
authors.initials: D
authors.lastname: Saffarini
authors.forename: H Peter
authors.initials: HP
authors.lastname: Lu
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D008565:Membrane Proteins / Q000737:chemistry; D018625:Microscopy, Atomic Force; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D020592:Shewanella / Q000737:chemistry; D013059:Spectrum Analysis, Raman
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D010088:Oxidoreductases