Single-Cell Biophysics: Measurement, Modulation, and Modeling

Single-Cell Biophysics: Measurement, Modulation, and Modeling

Poster Abstracts

66-POS Board 33 Stator Stoichiometry and Mechanosensitivity of the Bacterial Flagellar Motor Probed by Load Manipulation Ashley L. Nord , Emily Gachon, Alessandro Barducci, Francesco Pedaci. Centre de Biochimie Structurale, Montpellier, France. The bacterial flagellar motor (BFM) is the multi-component complex which powers the swimming and swarming of many motile bacteria. The BFM structure, many details of which are still unknown, displays a rich dynamic behavior in terms of exchange and conformational change of its internal components. The torque of this rotary motor is provided by stators, ion motive force powered ion channels which are known to assemble and disassemble dynamically in the BFM. Recently, it has been observed that this turn-over is mechano-sensitive, with the number of engaged stators dependent upon the external load acting on the motor. Despite their central role in the function of the BFM, a systematic study of the stator dynamics, as a function of the external parameters in unperturbed motors, is lacking. Here we provide a quantitative and non- invasive measurement of the temporal behavior of the stators active in the BFM of E. coli , by estimating stator stoichiometry from high-resolution single-motor torque traces, quantifying for the first time the dependence between stator number and external load at steady-state. Furthermore, a rapid and controlled change in the external load, applied via a magnetic field, allows us to directly probe BFM mechano-sensitivity, systematically triggering and detecting stator association and dissociation. We incorporate these results into an adsorption model of stator kinetics, providing the first step into understanding the mechanism of mechano-sensitivity of the BFM.

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