Mechanical properties of peptidoglycan as determined from bacterial thread

Thwaites, J. J.; Mendelson, Neil H.

doi:10.1016/0141-8130(89)90069-x

Cited by 43 publications

(39 citation statements)

References 12 publications

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“…The significance of these results and those of earlier experiments (18,25,26) is discussed in relation to the molecular organization of the bacterial cell wall. These results are not in conflict with the presently accepted picture.…”

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confidence: 73%

“…4 and 5 are the corresponding data at the three humidity levels for cell walls in threads drawn from TB medium and not washed in any way (25). The concentration of NaCl in TB medium is 83 mM.…”

Section: Resultsmentioning

confidence: 99%

“…The mechanical properties of bacterial cell wall are greatly influenced by the degree to which the walls are hydrated (25,26). They are also affected by the presence of residual growth medium (18,26).…”

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confidence: 99%

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Mechanical properties of Bacillus subtilis cell walls: effects of ions and lysozyme

1991

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Bacterial threads of BacUlus subtilis have been immersed in, and redrawn from, water of various pH values, in solutions of (NH4)2SO4 and NaCI of various concentrations, and in Iysozyme solutions. The changes in the tensile strength, elastic modulus, and other mechanical properties of the bacterial cell wall due to these treatments were obtained. The data show that change in pH has little effect but that as the salt concentration is increased, the cell walls become more ductile. A high salt concentration (1 M NaCI) can reduce the modulus by a factor of 26 to 13.5 MPa at 81% relative humidity and the strength by a factor of only 2.5. Despite attacking the septal-wall region of the cellular filaments, Iysozyme has no effect on the mechanical properties. There is no significant change in the stress relaxation behavior due to any of the treatments. The dependence of mechanical properties on the salt concentration is discussed in terms of the polyelectrolyte nature of cell walls. The evidence presented in this and the accompanying paper (J. J. Thwaites and U. C. Surana, J. Bacteriol., 173:197-203, 1991) supports the idea that the peptidoglycan in bacterial cell wall is an entanglement network with a large degree of molecular flexibility, with some order but no regular structure.

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confidence: 73%

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confidence: 99%

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Mechanical properties of Bacillus subtilis cell walls: effects of ions and lysozyme

1991

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“…Like flagella, fibers of B. subtilis cells have adequate material properties (e.g. Young's modulus [21]) and aspect ratio to display instabilities like those described here. More complex phenomena are associated with instabilities of rotating helical flagella, as described elsewhere [28].…”

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confidence: 99%

“…The rightmost form in (6) shows readily the frequency scales for systems of varying length and stiffness. Consider the elastica DNA (L p ∼ 5 × 10 −6 cm, a ∼ 10 −7 cm), microtubules (L p ∼ 0.5 cm, a ∼ 10 −6 cm), and bacterial filaments (L p ∼ 25 cm, a ∼ 3 × 10 −5 cm) [21].…”

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confidence: 99%

Twirling and Whirling: Viscous Dynamics of Rotating Elastic Filaments

2000

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Motivated by diverse phenomena in cellular biophysics, including bacterial flagellar motion and DNA transcription and replication, we study the overdamped nonlinear dynamics of a rotationally forced filament with twist and bend elasticity. Competition between twist injection, twist diffusion, and writhing instabilities is described by a novel pair of coupled PDEs for twist and bend evolution. Analytical and numerical methods elucidate the twist/bend coupling and reveal two dynamical regimes separated by a Hopf bifurcation: (i) diffusion-dominated axial rotation, or twirling, and (ii) steady-state crankshafting motion, or whirling. The consequences of these phenomena for selfpropulsion are investigated, and experimental tests proposed.PACS numbers: 46.70.Hg, 47.15.Gf, Dynamics and stability of rotationally forced elastic filaments arise in several important biological settings involving bend and twist elasticity at low Reynolds number. In the context of DNA replication, when two daughter strands are produced from a duplex, it was noted [1] long ago that energy dissipation for rotations about the filament axis is so much smaller than that for transverse motions that axial "speedometer-cable" motions are favored, and are energetically and topologically feasible. During DNA transcription, in which a polymerase protein moves down the double-stranded filament, progressive unwinding of the helix can lead to an accumulation of local twist that may induce "writhing" instabilities of the filament [2]. Energetic and dynamical aspects of these processes are of great current interest [3,4].At the cellular level, bacteria are propelled through fluids by helical flagella turned by rotary motors in the cell wall [5]. Recent studies [6] have revealed the details of two competing crystal structures assumed by flagellin, the protein building block of flagella, corresponding to helices of opposite chirality. Both local and distributed torques can change the conformation of flagella; during swimming these motors episodically reverse direction [7], and the resultant torques can induce transformations between these states [8], while uniform flow past a pinned flagellum may induce such chirality inversions [9].To elucidate fundamental processes common to these systems, we consider here the model problem shown in Fig. 1: a slender elastic filament in a fluid of viscosity η, rotated at one end at frequency ω 0 with the other free. We study competition between three processes: twist injection at the rotated end, twist diffusion, and writhing. Analytical and numerical methods reveal two dynamical regimes of motion: twirling, in which the straight but twisted rod rotates about its centerline, and whirling, in which the centerline of the rod writhes and crankshafts around the rotation axis in a steady state.This work is a natural outgrowth of recent studies of forced elastica in the plane [10,11], and dynamic twistbend coupling [12][13][14]. The balance considered between elastic and viscous stresses complements that between elasticity and ...

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Macromolecular Asymmetry

Galloway¹

2007

Ciba Foundation Symposium 162 ‐ Biological Asymmetry and Handedness

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Mechanical properties of peptidoglycan as determined from bacterial thread

Cited by 43 publications

References 12 publications

Mechanical properties of Bacillus subtilis cell walls: effects of ions and lysozyme

Mechanical properties of Bacillus subtilis cell walls: effects of ions and lysozyme

Twirling and Whirling: Viscous Dynamics of Rotating Elastic Filaments

Macromolecular Asymmetry

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