Mechanical Behaviour of Bacterial Cell Walls

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

doi:10.1016/s0065-2911(08)60008-9

Cited by 77 publications

(65 citation statements)

References 75 publications

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“…Our model also predicts that when the turgor pressure is removed, the cell shrinks up to 50% in volume and 20% longitudinally and radially. These predictions are in accord with experimental observations (21,32).…”

supporting

confidence: 91%

“…In E. coli, for example, it appears that PG strands are perpendicular to the longitudinal direction, which suggests that the mechanical properties of the cell wall are anisotropic. Mechanical constants in the hoop (radial) and longitudinal directions are different (12,21,22). Anisotropic properties of the cell wall can be modeled by introducing different bending and stretching constants in the circumferential and longitudinal directions.…”

Section: The Modelmentioning

confidence: 99%

“…The polar cap regions, however, turn over much more slowly during the growing phase of the bacterium (20). In B. subtilis, which lacks an outer membrane, removed old strands have been detected in the surrounding medium (17,21). In E. coli, which has an outer membrane, old strands are probably recycled in the growth mechanism (18,19).…”

mentioning

confidence: 99%

“…In Gram-positive bacteria, such as B. subtilis, the PG layer is relatively thick (Ϸ40 nm) (24) and mechanically rigid. In Gram-negative bacteria, such as E. coli, the PG layer is thin (Ϸ6 nm) (21), and the wall is significantly softer.…”

mentioning

confidence: 99%

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Z-ring force and cell shape during division in rod-like bacteria

Lan

Wolgemuth

Sun

2007

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

119

122

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The life cycle of bacterial cells consists of repeated elongation, septum formation, and division. Before septum formation, a division ring called the Z-ring, which is made of a filamentous tubulin analog, FtsZ, is seen at the mid cell. Together with several other proteins, FtsZ is essential for cell division. Visualization of strains with GFP-labeled FtsZ shows that the Z-ring contracts before septum formation and pinches the cell into two equal halves. Thus, the Z-ring has been postulated to act as a force generator, although the magnitude of the contraction force is unknown. In this article, we develop a mathematical model to describe the process of growth and Z-ring contraction in rod-like bacteria. The elasticity and growth of the cell wall is incorporated in the model to predict the contraction speed, the cell shape, and the contraction force. With reasonable parameters, the model shows that a small force from the Z-ring (8 pN in Escherichia coli) is sufficient to accomplish division.bacterial cell division ͉ FtsZ-ring ͉ mathematical model ͉ peptidoglycan synthesis I n rod-like bacteria, such as Escherichia coli and Bacillus subtilis, a conserved cell division gene is FtsZ, which forms a filamentous ring structure (Z-ring) at the mid cell before division (1, 2). The positioning of the Z-ring at the mid cell in E. coli is related to spatial-temporal oscillations in the MinCDE system (3-5). For the actual division step, the radius of the Z-ring is seen to decrease over several minutes, after which a septum is formed and the bacterium separates into two daughter cells (1, 6). It has been postulated that the Z-ring generates forces and ''pinches'' the cell into halves (7), although whether FtsZ generates force is debatable. In addition to the Fts family of proteins, other proteins are also essential for cell division. In particular, disabling peptidoglycan (PG) synthesis proteins or penicillin binding proteins (PBP) just before division stops cytokinesis (8, 9). A systematic study showed that some PBPs are localized near the Z-ring during division (10). Therefore, cell wall synthesis is important in cell division. The mechanics and the dynamics of the cell wall must be considered on an equal footing for quantifying bacterial cell division.Growth and synthesis of the bacterial cell wall is a complex process. The wall is composed of saccharide strands interconnected by polypeptides (7,(11)(12)(13). Indeed, families of PBPs are found in bacteria, with some localized near the furrow during division and some uniformly distributed (10,14,15). Coordinated activity of PBPs synthesizes new PG strands, cross-linking them into the existing wall structure. In a proposed growth model, old strands are also depolymerized, thereby removing them from the wall structure (a process that we will generically call ''turnover'') (7, 11, 16), although models for E. coli growth without turnover also have been proposed (12, 13). Using radio-active labeling, turnover in the PG layer has been investigated (17-19). It was found that the c...

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supporting

confidence: 91%

Section: The Modelmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Z-ring force and cell shape during division in rod-like bacteria

Lan

Wolgemuth

Sun

2007

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

119

122

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“…A nematode sperm cell crawls at about 1 µm s −" by assembling the major sperm protein into filaments (Italiano et al, 2001 ;Mahadevan & Matsudaira, 2000). Macrofibres move by insertion of new cell wall polymers into the fabric of the wall (Thwaites & Mendelson, 1991) in cells throughout the entire fibre.…”

Section: Discussionmentioning

confidence: 99%

Motions caused by the growth of Bacillus subtilis macrofibres in fluid medium result in new forms of movement of the multicellular structures over solid surfaces

Mendelson

Sarlls²,

Thwaites³

2001

Microbiology

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Bacillus subtilis macrofibres, highly ordered multicellular structures, undergo twisting and writhing motions when they grow in fluid medium as a result of forces generated by the elongation of individual cells. Macrofibres are denser than the fluid medium in which they are cultured, consequently they settle to the bottom of the growth chamber and grow in contact with it. The ramifications of growth on plastic and glass surfaces were examined. Macrofibres were observed to rotate about a vertical axis near the centre of their length in a chiral-specific direction. Right-handed fibres rotated clockwise on plastic surfaces at approximately 4S min N1 , left-handed structures of lower twist rotate anti-clockwise at about half that rate. Very large ball structures produced late in macrofibre formation perched on many small protruding fibres but rotated only when driven by large fibres attached to their periphery. Closer examination showed that fibres made contact with surfaces at only a few points along their length (between 1 and 6 on glass). The regions in contact with the surface changed periodically as a result of rotation of the fibre shaft caused by growth. Every time the weight of a fibre transferred from one contact point to another, each section of the fibre took a small step approximately proportional to its distance from the fibre mid-point. The net result was a rolling of each section over the surface so that the fibre rotation about a vertical axis was produced. Macrofibres also took large steps when part of the structure rose off the floor, swept through an arc in the fluid and then returned to the floor at a new location. The rate of movement during a large step, measured as the change of angle between the moving and stationary portions of the fibre, was 5S s N1 . These observations reveal that the forces derived from helical growth that lead to macrofibre formation also cause characteristic macrofibre motion that differs from classical motility.

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Intracellular Handedness in Ciliates

Frankel

2007

Ciba Foundation Symposium 162 ‐ Biological Asymmetry and Handedness

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Mechanical Behaviour of Bacterial Cell Walls

Cited by 77 publications

References 75 publications

Z-ring force and cell shape during division in rod-like bacteria

Z-ring force and cell shape during division in rod-like bacteria

Motions caused by the growth of Bacillus subtilis macrofibres in fluid medium result in new forms of movement of the multicellular structures over solid surfaces

Intracellular Handedness in Ciliates

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