Single-Cell Biophysics: Measurement, Modulation, and Modeling

Single-Cell Biophysics: Measurement, Modulation, and Modeling

Poster Abstracts

42-POS Board 21 Single-Cell Respiration Rate Measurements on Bacteria Krishna Ojha, John Ertle, Michael C. Konopka . The University of Akron, Akron, OH, USA.

Respiration can be an indicator of physiological state and therefore is an excellent target for analysis of cell-to-cell variation within a sample. Single-cell respiration rate measurements are made by first sealing cells in 2-500 pL wells in a glass chip designed to isolate single cells and then monitoring the oxygen consumption over time. A phosphorescent Pt-porphyrin dye acts as the oxygen sensor since the lifetime of the dye’s excited state depends on the oxygen concentration in the sample. Microspheres embedded with the Pt-porphyrin are loaded into the wells and all measurements are made on a fluorescence microscope. Samples can also be reoxygenated to replicate measurements or perform measurements on the same cells with altered conditions. The respiration rates of individual bacterial cells from the same isogenic culture can have as much as a four-fold difference. Separate measurements also show large variations in membrane diffusion coefficients between different cells. We are currently investigating the role membrane fluidity may play in the variation in respiration rates found between individual cells. In particular, determining if it is the direct mobility of a component of the electron transport chain (ETC), such as the electron carrier ubiquinone, that is limiting the respiration rates. Alternatively, heterogeneity in respiration rates could be caused by differences in the segregation of oxidative phosphorylation complexes caused by variations in membrane composition.

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