Torque, but not FliL, regulates mechanosensitive flagellar motor-function

Chawla, Ravi; Ford, Katie; Lele, Pushkar P.

doi:10.1038/s41598-017-05521-8

Cited by 55 publications

(61 citation statements)

References 44 publications

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“…While catch bonds are often directional or asymmetrically directional (51), the catch-bond behavior of the stator may prove to be symmetrically bidirectional. Finally, FliL is a membrane protein which associates with the stator and rotor, although its exact function is still poorly defined (17,(52)(53)(54). The potential role of FliL with respect to the stator's mechanosensitivity remains to be discovered.…”

Section: Discussionmentioning

confidence: 99%

A Catch-Bond Drives Stator Mechanosensitivity in the Bacterial Flagellar Motor

Nord

Gachon

Pérez-Carrasco

et al. 2018

Biophysical Journal

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The bacterial flagellar motor (BFM) is the rotary motor that rotates each bacterial flagellum, powering the swimming and swarming of many motile bacteria. The torque is provided by stator units, ion motive force-powered ion channels known to assemble and disassemble dynamically in the BFM. This turnover is mechanosensitive, with the number of engaged units dependent on the viscous load experienced by the motor through the flagellum. However, the molecular mechanism driving BFM mechanosensitivity is unknown. Here, we directly measure the kinetics of arrival and departure of the stator units in individual motors via analysis of high-resolution recordings of motor speed, while dynamically varying the load on the motor via external magnetic torque. The kinetic rates obtained, robust with respect to the details of the applied adsorption model, indicate that the lifetime of an assembled stator unit increases when a higher force is applied to its anchoring point in the cell wall. This provides strong evidence that a catch bond (a bond strengthened instead of weakened by force) drives mechanosensitivity of the flagellar motor complex. These results add the BFM to a short, but growing, list of systems demonstrating catch bonds, suggesting that this "molecular strategy" is a widespread mechanism to sense and respond to mechanical stress. We propose that force-enhanced stator adhesion allows the cell to adapt to a heterogeneous environmental viscosity and may ultimately play a role in surface-sensing during swarming and biofilm formation.bacterial flagellar motor | molecular motor | mechanosensitivity | catch bond | Escherichia coli T he bacterial flagellar motor (BFM) is a large molecular complex found in many species of motile bacteria which actively rotates each flagellum of the cell, enabling swimming, chemotaxis, and swarming (1, 2). The rotor of the BFM is embedded within and spans the cellular membranes, coupling rotation to the extracellular hook and flagellar filament. Multiple transmembrane complexes, called stator units, are anchored around the perimeter of the rotor and bound to the rigid peptidoglycan (PG) layer (3-5). By harnessing the ion motive force, the stator units are responsible for torque generation, acting upon the common ring formed by FliG proteins on the cytosolic side of the rotor (Fig. 1A) (6, 7).Several studies have revealed the continuous exchange of various BFM molecular constituents (8-10), demonstrating that a static model for the BFM structure is not adequate. A prime example, and in contrast to macroscopic rotary motors, the stator of the BFM is dynamic; while each bound stator unit acts upon the rotor independently (11, 12), their stoichiometry in the motor varies. Once anchored around the rotor, stator units dynamically turn over, eventually diffusing away in the inner membrane (10). Each additional recruited stator unit increases the total torque and thus the measured rotational speed of the motor (11, 13), and up to 11 units have been observed to engage in an individual motor in Esche...

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Section: Discussionmentioning

confidence: 99%

A Catch-Bond Drives Stator Mechanosensitivity in the Bacterial Flagellar Motor

Nord

Gachon

Pérez-Carrasco

et al. 2018

Biophysical Journal

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“…When a much higher force is applied to the anchoring point of MotB C-PGB in the rigid PG layer, a dissociation rate of the MotAB complex becomes much slower, thereby increasing the bound lifetime of the assembled stator units in the motor. In contrast, when a much lower force is applied, the dissociation rate of the MotAB complex becomes much faster, thereby decreasing the bound lifetime of the assembled stator units (Chawla et al, 2017;Nord et al, 2017). These suggest that the binding affinity of each MotB C-PGB domain for the rigid PG layer is increased by the applied force when external load is high enough (Chawla et al, 2017;Nord et al, 2017).…”

Section: Control Of Stator Assembly In the Flagellar Motormentioning

confidence: 99%

“…When the external load becomes low enough, several MotAB complexes dissociate from the motor (Lele et al, 2013;Tipping et al, 2013). Force applied to the anchoring point of MotB C-PGB in the rigid PG layer affects the assembly-disassembly equilibrium of the MotAB complex (Chawla et al, 2017;Nord et al, 2017). Since helical rearrangements of the N-terminal portion of MotB C-PGB are responsible not only for anchoring MotB C-PGB to the PG layer but also for activating the H + channel (Kojima et al, 2018), MotB C-PGB must have a structural switch to regulate the number of active stator units in the motor in an applied force-dependent manner.…”

Section: Conclusion and Outlooksmentioning

confidence: 99%

Autonomous control mechanism of stator assembly in the bacterial flagellar motor in response to changes in the environment

Minamino

Terahara

Kojima

et al. 2018

Molecular Microbiology

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The bacterial flagellar motor is composed of a rotor and a transmembrane ion channel complex that acts as a stator unit. The ion channel complex consists of at least three structural parts: a cytoplasmic domain responsible for the interaction with the rotor, a transmembrane ion channel that forms a pathway for the transit of ions across the cytoplasmic membrane, and a peptidoglycan-binding (PGB) domain that anchors the stator unit to the peptidoglycan (PG) layer. A flexible linker connecting the ion channel and the PGB domain not only coordinates stator assembly with its ion channel activity but also controls the assembly of stator units to the motor in response to changes in the environment. When the ion channel complex encounters the rotor, the N-terminal portion of the PGB domain adopts a partially stretched conformation, allowing the PGB domain to reach and bind to the PG layer. The binding affinity of the PGB domain for the PG layer is affected by the force applied to its anchoring point and to the type of ionic energy source. In this review article, we will present current understanding of autonomous control mechanism of stator assembly in the bacterial flagellar motor.

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“…We next demonstrated that it is possible to use APP to physically separate progenitor from differentiated cells by linking motility to the presence/absence of the target plasmid. To do this, we used a motile strain of E. coli (HCB84) carrying a motA mutation known to disrupt motility 46 .…”

Section: Physical Separation Of Differentiated Cellsmentioning

confidence: 99%

Synthetic pluripotent bacterial stem cells

Molinari

Shis

Chappell

et al. 2018

Preprint

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We describe a synthetic genetic circuit for controlling asymmetric cell division in E. coli in which a progenitor cell creates a differentiated daughter cell while retaining its original phenotype.Specifically, we engineered an inducible system that can bind and segregate plasmid DNA to a single position in the cell. Upon cell division, co-localized plasmids are kept by one and only one of the daughter cells. The other daughter cell receives no plasmid DNA and is hence irreversibly differentiated from its sibling. In this way, we achieved asymmetric cell division through asymmetric plasmid partitioning. We then used this system to achieve physical separation of genetically distinct cells by tying motility to differentiation. Finally, we characterized an orthogonal inducible circuit that enables the simultaneous asymmetric partitioning of two plasmid species, resulting in cells that have four distinct differentiated states. These results point the way towards engineering multicellular systems from prokaryotic hosts. biochemical or physical tasks throughout the organism. In multicellular eukaryotes, cellular differentiation is generally achieved through complex regulatory networks that utilize transcriptional regulation, post-transcriptional modifications, and chromatin remodeling 19-21 . To differentiate asymmetrically, a progenitor cell (such as a stem cell) senses chemical cues in the environment to alter the transcriptional landscape in the daughter cell. This transcriptional rearrangement of the daughter cell is complete enough that de-differentiation is rare and reproducible in the lab only through the very specific and simultaneous induction of many genes 22 .Several attempts have been made to create synthetic bacteria that have multiple stable transcriptional profiles 3,23 . The first of these was the corepressive toggle switch in E. coli designed by Gardner and colleagues 3 . However, the corepressive toggle does not create irreversibly differentiated cell types. It is sensitive to intrinsic and extrinsic sources of gene regulatory noise 3,24-27 , and can only transiently maintain one state before stochastically switching back to the other.Others have used recombinases 28 to alter DNA sequences permanently, or controllably alter the copy numbers of plasmids to affect gene regulation and cell differentiation 29,30 .Here, we repurposed two key elements of the chromosome partitioning system (par) of Caulobacter crescentus 31 to create asymmetric cell division and irreversible differentiation in E. coli. The par system is common in prokaryotes and is principally responsible for partitioning low copy number plasmids or chromosomes upon cell division 32 . The par systems generally rely on the interaction of three elements: a centromere-like cis-acting sequence, parS, present on the plasmid/chromosome; a centromere-binding trans-acting protein, ParB; and an NTPase, usually called ParA 33 . The initial step is the formation of the partition complex, in which all the copies of the plasmid or chromosomal DNA are gat...

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Torque, but not FliL, regulates mechanosensitive flagellar motor-function

Cited by 55 publications

References 44 publications

A Catch-Bond Drives Stator Mechanosensitivity in the Bacterial Flagellar Motor

A Catch-Bond Drives Stator Mechanosensitivity in the Bacterial Flagellar Motor

Autonomous control mechanism of stator assembly in the bacterial flagellar motor in response to changes in the environment

Synthetic pluripotent bacterial stem cells

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