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Single-Cell Biophysics: Measurement, Modulation, and Modeling
Poster Abstracts
119
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.