Stator Dynamics Depending on Sodium Concentration in Sodium-Driven Bacterial Flagellar Motors

Tsai Shun Lin, Seiji Kojima, Hajime Fukuoka, Akihiko Ishijima, Michio Homma, Chien Jung Lo

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Bacterial flagellar motor (BFM) is a large membrane-spanning molecular rotary machine for swimming motility. Torque is generated by the interaction between the rotor and multiple stator units powered by ion-motive force (IMF). The number of bound stator units is dynamically changed in response to the external load and the IMF. However, the detailed dynamics of stator unit exchange process remains unclear. Here, we directly measured the speed changes of sodium-driven chimeric BFMs under fast perfusion of different sodium concentration conditions using computer-controlled, high-throughput microfluidic devices. We found the sodium-driven chimeric BFMs maintained constant speed over a wide range of sodium concentrations by adjusting stator units in compensation to the sodium-motive force (SMF) changes. The BFM has the maximum number of stator units and is most stable at 5 mM sodium concentration rather than higher sodium concentration. Upon rapid exchange from high to low sodium concentration, the number of functional stator units shows a rapidly excessive reduction and then resurrection that is different from predictions of simple absorption model. This may imply the existence of a metastable hidden state of the stator unit during the sudden loss of sodium ions.

Original languageEnglish
Article number765739
JournalFrontiers in Microbiology
StatePublished - 26 Nov 2021


  • bacterial flagellar motor
  • membrane protein
  • perfusion
  • sodium-motive force
  • stator exchange


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