Abstract
The rotary flagellar motor of Escherichia coli bacterium switches stochastically between the clockwise (CW) and counterclockwise (CCW) direction. We found that the CW and CCW intervals could be described by a gamma distribution, suggesting the existence of hidden Markov steps preceding each motor switch. Power spectra of time series of switching events exhibited a peaking frequency instead of the Lorentzian profile expected from standard kinetic two-state models. Our analysis indicates that the number of hidden steps may be a key dynamical parameter underlying the switching process in a single bacterial motor as well as in large cooperative molecular systems.
Highlights
The rotary flagellar motor of Escherichia coli bacterium switches stochastically between the clockwise (CW) and counterclockwise (CCW) direction
We found that the CW and CCW intervals could be described by a gamma distribution, suggesting the existence of hidden Markov steps preceding each motor switch
Our analysis indicates that the number of hidden steps may be a key dynamical parameter underlying the switching process in a single bacterial motor as well as in large cooperative molecular systems
Summary
Ekaterina A., Thierry Emonet, Heungwon Park, and Philippe Cluzel. 2006. Hidden stochastic nature of a single bacterial motor. In this Letter, we measure and analyze long binary time series of switching events from individual motors to characterize experimentally the underlying stochastic nature of this classic allosteric system at the level of a single motor. In our experiment, the concentration of the CheY* that binds to the subunits of the ring is not controlled by the chemotaxis network but stably preexpressed from an inducible vector expressing the CheYD13K gene [11] Under these conditions the concentration of CheY* does not exhibit temporal correlation at long time scales as described in [10,11].
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