Effect of Surface Binding on Individual Bacterial Cells: Raman and AFM Approaches

Tuesday, 3 October 2017: 09:40
National Harbor 5 (Gaylord National Resort and Convention Center)
N. Lebedev (Naval Research Laboratory, CBMSE) and L. M. Tender (Naval Research Laboratory)
Bacterial cell polarity is an internal cell asymmetry that correlates with the cell ability to sense energy and metabolite sources, chemical signals, quorum signals, toxins, and movement in the desired directions. This ability also plays central role in cell attachment to various surfaces and biofilm formation. Biochemical analysis and molecular imaging demonstrate that sensing of energy and nutrients by the cell correlates with asymmetric protein, lipid and other molecule distributions within the cell. In the present work, we develop an experimental approach and analyze how attachment to inorganic mineral, mica affects Cyt redox state inside individual G. sulfurreducens cells. The approach is based on confocal Raman microscopy allowing for simultaneous detection of Raman spectra of individual bacterial cell and the substrate and allowing for precise estimation of the border between them. Applying Gaussian deconvolution and principal component analysis we are able to identify spectral signatures of cytochrome redox states and their intracellular location. Our results demonstrate that attachment of G. sulfurreducens cells to a muscovite (mica) selectively changes Cyt redox state at the cell side facing the mineral. This leads to the formation of a gradient of redox potential needed for directed electron transfer within the cell. Our results open the possibility for analyzing electrochemical potentials inside individual bacterial cells. They indicate that Cyt redox state might be a driving force switching cell metabolic activity that leads to irreversible cell attachment to electrode, cell-to-cell association, and biofilm formation.