How Salmonella typhimurium measures the length of flagellar filaments

Keener, James P.

doi:10.1007/s11538-005-9033-0

Cited by 20 publications

(16 citation statements)

References 13 publications

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“…Derivation of this formula is based on an injection-diffusion model where flagellin monomers, which are at least partially α-helical inside the channel (Shibata et al, 2007), are pushed by a pmf-driven export apparatus into the channel and move diffusively in one dimension through the length of the flagellum (Stern and Berg, 2013; Keener, 2006). An analytical expression for the flagellum length dependent growth rate is based on a continuum injection-diffusion model for the growth of flagellar filaments.…”

Section: Resultsmentioning

confidence: 99%

Bacterial flagella grow through an injection-diffusion mechanism

Renault

Abraham

Bergmiller

et al. 2017

eLife

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The bacterial flagellum is a self-assembling nanomachine. The external flagellar filament, several times longer than a bacterial cell body, is made of a few tens of thousands subunits of a single protein: flagellin. A fundamental problem concerns the molecular mechanism of how the flagellum grows outside the cell, where no discernible energy source is available. Here, we monitored the dynamic assembly of individual flagella using in situ labelling and real-time immunostaining of elongating flagellar filaments. We report that the rate of flagellum growth, initially ∼1,700 amino acids per second, decreases with length and that the previously proposed chain mechanism does not contribute to the filament elongation dynamics. Inhibition of the proton motive force-dependent export apparatus revealed a major contribution of substrate injection in driving filament elongation. The combination of experimental and mathematical evidence demonstrates that a simple, injection-diffusion mechanism controls bacterial flagella growth outside the cell.DOI: http://dx.doi.org/10.7554/eLife.23136.001

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Section: Resultsmentioning

confidence: 99%

Bacterial flagella grow through an injection-diffusion mechanism

Renault

Abraham

Bergmiller

et al. 2017

eLife

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“…Taken together, both Western blots and structural analyses indicate that CsrA Bb specifically impacts PF synthesis by regulating FlaB synthesis and filament length. In the enteric bacteria, the regulation of flagellar filament length is proposed to be measured based on the rate of the secretion of FlgM (Keener, 2006). During the early synthesis of flagellar filament, the secretion of FlgM through the completed basal body‐hook complex is rapid.…”

Section: Discussionmentioning

confidence: 99%

Carbon storage regulator A (CsrABb) is a repressor of Borrelia burgdorferi flagellin protein FlaB

Sze

Morado²,

Li³

et al. 2011

Molecular Microbiology

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SUMMARY The Lyme disease spirochete Borrelia burgdorferi lacks the transcriptional cascade control of flagellar protein synthesis common to other bacteria. Instead, it relies on a post-transcriptional mechanism to control its flagellar synthesis. The underlying mechanism of this control remains elusive. A recent study reported that the increased level of BB0184 (CsrABb; a homolog of carbon storage regulator A) substantially inhibited the accumulation of FlaB, the major flagellin protein of B. burgdorferi. In this report, we deciphered the regulatory role of CsrABb on FlaB synthesis and the mechanism involved by analyzing two mutants, csrABb− (a deletion mutant of csrABb) and csrABb+ (a mutant conditionally over-expressing csrABb). We found that FlaB accumulation was significantly inhibited in csrABb+ but was substantially increased in csrABb−. In contrast, the levels of other flagellar proteins remained unchanged. Cryo-electron tomography and immuno-fluorescence microscopic analyses revealed that the altered synthesis of CsrABb in these two mutants specifically affected flagellar filament length. The leader sequence of flaB transcript contains two conserved CsrA-binding sites, with one of these sites overlapping the Shine-Dalgarno sequence. We found that CsrABb bound to the flaB transcripts via these two binding sites, and this binding inhibited the synthesis of FlaB at the translational level. Taken together, our results indicate that CsrABb specifically regulates the periplasmic flagellar synthesis by inhibiting translation initiation of the flaB transcript.

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“…The latter depends on the diffusion of actin monomers to the tip, which results in a length-dependent rate of assembly. It has also been suggested that a diffusion-induced length dependence of the assembly rate plays a role in the control of the hook length in bacterial flagella (11). A different balance mechanism appears to control the length of microtubules in yeast, where kinesin motors move processively to the microtubule tips where they catalyze disassembly.…”

Section: Introductionmentioning

confidence: 99%

Delayed Feedback Model of Axonal Length Sensing

Karamched

Bressloff

2015

Biophysical Journal

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A fundamental question in cell biology is how the sizes of cells and organelles are regulated at various stages of development. Size homeostasis is particularly challenging for neurons, whose axons can extend from hundreds of microns to meters (in humans). Recently, a molecular-motor-based mechanism for axonal length sensing has been proposed, in which axonal length is encoded by the frequency of an oscillating retrograde signal. In this article, we develop a mathematical model of this length-sensing mechanism in which advection-diffusion equations for bidirectional motor transport are coupled to a chemical signaling network. We show that chemical oscillations emerge due to delayed negative feedback via a Hopf bifurcation, resulting in a frequency that is a monotonically decreasing function of axonal length. Knockdown of either kinesin or dynein causes an increase in the oscillation frequency, suggesting that the length-sensing mechanism would produce longer axons, which is consistent with experimental findings. One major prediction of the model is that fluctuations in the transport of molecular motors lead to a reduction in the reliability of the frequency-encoding mechanism for long axons.

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How Salmonella typhimurium measures the length of flagellar filaments

Cited by 20 publications

References 13 publications

Bacterial flagella grow through an injection-diffusion mechanism

Bacterial flagella grow through an injection-diffusion mechanism

Carbon storage regulator A (CsrABb) is a repressor of Borrelia burgdorferi flagellin protein FlaB

Delayed Feedback Model of Axonal Length Sensing

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