Hidden stochastic nature of a single bacterial motor
The bacterium E. coli has a rotary flagellar motor that switches between clockwise (CW) and counter-clockwise (CCW) motion in a stochastic manner. This study found that the intervals for the CW and CCW stages could be described by a Gamma distribution, and the authors suggest that this indicates there may be "hidden Markov steps" involved in the process of motor direction switching. The number of hidden steps seems to be a key dynamical parameter that determines the motor switching behavior in a bacterium cell as well as in large cooperative molecular systems more generally.
Connection to soft matter
It has been found that the CW bias, or the probability that the motor will rotate clockwise, increases nonlinearly with the concentration of the signaling molecule CheY-P. In this study the authors analyzed binary time series of motor direction switching events to quantitatively characterize the switching behavior.