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Mol Microbiol. 2015 Jun;96(5):993-1001. doi: 10.1111/mmi.12984. Epub 2015 Mar 31.

Dual stator dynamics in the Shewanella oneidensis MR-1 flagellar motor.

Author information

1
Max-Planck-Institute für terrestrische Mikrobiologie, Department of Ecophysiology, 35043, Marburg, Germany.
2
Biochemistry Department, University of Oxford, Oxford, OX1 3QU, UK.
3
Justus-Liebig-Universität Gießen, Department of Microbiology and Molecular Biology at the IFZ, Gießen, 35392, Germany.
4
Physics Department, University of Oxford, Oxford, OX1 3QU, UK.

Abstract

The bacterial flagellar motor is an intricate nanomachine which converts ion gradients into rotational movement. Torque is created by ion-dependent stator complexes which surround the rotor in a ring. Shewanella oneidensis MR-1 expresses two distinct types of stator units: the Na(+)-dependent PomA4 B2 and the H(+)-dependent MotA4 B2. Here, we have explored the stator unit dynamics in the MR-1 flagellar system by using mCherry-labeled PomAB and MotAB units. We observed a total of between 7 and 11 stator units in each flagellar motor. Both types of stator units exchanged between motors and a pool of stator complexes in the membrane, and the exchange rate of MotAB, but not of PomAB, units was dependent on the environmental Na(+)-levels. In 200 mM Na(+), the numbers of PomAB and MotAB units in wild-type motors was determined to be about 7:2 (PomAB:MotAB), shifting to about 6:5 without Na(+). Significantly, the average swimming speed of MR-1 cells at low Na(+) conditions was increased in the presence of MotAB. These data strongly indicate that the S. oneidensis flagellar motors simultaneously use H(+) and Na(+) driven stators in a configuration governed by MotAB incorporation efficiency in response to environmental Na(+) levels.

PMID:
25727785
DOI:
10.1111/mmi.12984
[Indexed for MEDLINE]
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