Analysis of force generation during flagellar assembly through optical trapping of free‐swimming <i>Chlamydomonas reinhardtii</i>

McCord, Rachel Patton; Yukich, John N.; Bernd, Karen K.

doi:10.1002/cm.20071

Cited by 36 publications

(26 citation statements)

References 22 publications

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“…0, the observed linear trend must change for short flagella. A related study [21] on the length dependence of the propulsive force showed approximately linear growth for ' * 5 m which also extrapolates to zero at ' $ 3 m. The approximate coincidence of the intercept for these three distinct observables suggests a common origin. Short and long flagella may behave differently due to structural inhomogeneities along the flagellum.…”

Section: Bothmentioning

confidence: 69%

Emergence of Synchronized Beating during the Regrowth of Eukaryotic Flagella

2011

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A fundamental issue in the biology of eukaryotic flagella is the origin of synchronized beating observed in tissues and organisms containing multiple flagella. Recent studies of the biflagellate unicellular alga Chlamydomonas reinhardtii provided the first evidence that the interflagellar coupling responsible for synchronization is of hydrodynamic origin. To investigate this mechanism in detail, we study here synchronization in Chlamydomonas as its flagella slowly regrow after mechanically induced self-scission. The duration of synchronized intervals is found to be strongly dependent on flagellar length. Analysis within a stochastic model of coupled phase oscillators is used to extract the length dependence of the interflagellar coupling and the intrinsic beat frequencies of the two flagella. Physical and biological considerations that may explain these results are proposed. DOI: 10.1103/PhysRevLett.107.148103 PACS numbers: 87.16.Qp, 05.45.Xt, 47.63.Àb, 87.18.Tt From unicellular organisms as small as a few microns to the largest vertebrates on Earth, we find groups of beating flagella or cilia that exhibit striking spatiotemporal organization. This may take the form of precise frequency and phase locking, as frequently found in the swimming of green algae [1], or beating with long-wavelength phase modulations known as metachronal waves, seen in ciliates such as Paramecium [2] and in our own respiratory systems. The remarkable similarity in the underlying molecular structure of flagella across the whole eukaryotic world leads naturally to the hypothesis that a similarly universal mechanism might be responsible for synchronization. Although this mechanism is poorly understood, one appealing hypothesis is that it results from hydrodynamic interactions between flagella.The role of hydrodynamics in synchronization has been the subject of intense theoretical investigation in the half century since the seminal work of Taylor [3] showed that phase synchronization of nearby undulating sheets minimizes viscous dissipation. Although minimizing dissipation is not a general principle from which to derive dynamics, a growing body of work has identified requirements for synchronization within minimal models involving systems of rotating spheres or helices [4][5][6]. It is now known that oscillators with more than one degree of freedom or those with suitable internal forcing can be synchronized by hydrodynamics [6,7]. Various levels of coordination are also found with more realistic models of flagella [8], which rely necessarily on simplified internal driving of the filaments. Nevertheless, these complex models yield important clues to the generation and regulation of flagellar motion [9].Experimental progress has lagged behind that of theory, due in large part to the challenge of finding a sufficiently simple model system that can be studied under an appropriately broad set of experimental conditions. But recent work [10] on Chlamydomonas reinhardtii (CR, Fig. 1), a biflagellate green alga well developed as a model to stud...

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Section: Bothmentioning

confidence: 69%

Emergence of Synchronized Beating during the Regrowth of Eukaryotic Flagella

2011

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“…algae. 52 Repeated trapping and releasing did not appear to damage the S. typhimurium cells, as indicated by consistent stall forces that were measured repeatedly for the same cell (data not shown). The majority of the wild-type SJW1103 cells were difficult to trap in the viscous medium and had an average stall force of more than 2.0 W ( Table 3).…”

Section: Measurement Of Stall Force In Viscous Aqueous Medium By Optimentioning

confidence: 83%

“…[76][77][78] Measurement of power required to stall cells using optical tweezers A BioRyx 200 optical trap with a 1064 nm laser source (Arryx, Chicago, IL) was used to trap bacterial cells and monitor their propulsive forces. Previous studies have shown that near-IR (790-1064 nm) wavelengths are relatively harmless for trapping live cells, 45,52,79 and the wavelength of 1064 nm is safe for use with live bacterial cells. A Nikon Eclipse TE2000U inverted epifluorescence microscope with a 60× (oil immersion) objective, equipped with a SenTech digital CCD camera, model STC630 (Sensor Technologies America, Carrollton, TX), was used to record images and movies of trapped S. typhimurium bacteria expressing flagellin variants.…”

Section: Light Microscopy and Swimming Velocity Analysismentioning

confidence: 99%

A Deletion Variant Study of the Functional Role of the Salmonella Flagellin Hypervariable Domain Region in Motility

Malapaka

Adebayo

Tripp

2007

Journal of Molecular Biology

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“…We found that in the interior of the fluid, without flow, the bacterium could only be stably trapped in the vertical direction, along the trapping axis. In this configuration, it was feasible to determine the threshold of the trapping force and relate it to the maximum of the thrust (22). However, the method is not suitable for measuring instantaneous thrust force acting on the cell body.…”

Section: Methodsmentioning

confidence: 99%

Swimming efficiency of bacterium Escherichia coli

Chattopadhyay

Moldovan

Yeung

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

259

251

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We use measurements of swimming bacteria in an optical trap to determine fundamental properties of bacterial propulsion. In particular, we directly measure the force required to hold the bacterium in the optical trap and determine the propulsion matrix, which relates the translational and angular velocity of the flagellum to the torques and forces propelling the bacterium. From the propulsion matrix, dynamical properties such as torques, swimming speed, and power can be obtained by measuring the angular velocity of the motor. We find significant heterogeneities among different individuals even though all bacteria started from a single colony. The propulsive efficiency, defined as the ratio of the propulsive power output to the rotary power input provided by the motors, is found to be Ϸ2%, which is consistent with the efficiency predicted theoretically for a rigid helical coil.bacterial flagellum ͉ bacterial propulsion ͉ propulsion matrix B acteria swim by rotating helical propellers called flagellar filaments. For Escherichia coli (E. coli), these filaments are several micrometers in length and 20 nm in diameter, organized in a bundle of four or five. Each flagellar filament is driven at its base by a reversible rotary engine, which turns at a frequency of Ϸ100 Hz (1). Many important properties of the swimming bacteria, such as their average swimming speed, the rotation rate of the flagellar bundle, and the torque generated by the molecular motor, have been determined (1)(2)(3)(4)(5)23). Other properties such as the translational and rotational drag coefficients of flagellar bundles, however, are difficult to measure, especially for intact cells. These parameters are significant for quantitative understanding of bacterial propulsion and are the subject of extensive mathematical analysis and computer simulations (6-10). In this work, we investigate the fundamental swimming properties of intact E. coli by using optical tweezers and an imposed external flow. We directly measure the force required to hold the bacterium and the angular velocities of the flagellar bundle and the cell body as a function of the flow velocity. The propulsion matrix, which relates the translational and angular velocity of the flagella to the forces and torques propelling the bacterium, can thus be determined one bacterium at a time. We find that the population-averaged matrix elements are in reasonable agreement with the resistive force theory for helical propellers (7), but there is a large variability even among bacteria of similar length grown from a single colony.The propulsion matrix also allows us to determine the propulsive efficiency , which is defined as the ratio of the propulsive power output (the part of the power used to push the cell body forward) to the rotary power input (the power used to rotate the flagellar bundle). We find the propulsive efficiency is strongly dependent on growth conditions but is not very sensitive to cell-body size. Despite the flexibility and internal friction between the filaments in the flagellar ...

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Analysis of force generation during flagellar assembly through optical trapping of free‐swimming Chlamydomonas reinhardtii

Cited by 36 publications

References 22 publications

Emergence of Synchronized Beating during the Regrowth of Eukaryotic Flagella

Emergence of Synchronized Beating during the Regrowth of Eukaryotic Flagella

A Deletion Variant Study of the Functional Role of the Salmonella Flagellin Hypervariable Domain Region in Motility

Swimming efficiency of bacterium Escherichia coli

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