Inside-to-outside growth and turnover of the wall of gram-positive rods

Koch, Arthur L.; Doyle, Ronald J.

doi:10.1016/s0022-5193(85)80169-7

Cited by 123 publications

(117 citation statements)

References 28 publications

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“…For the disintegration or fusion of cells with pores on the cell wall, the turnover of grampositive cell walls during cell growth will be under precise control. When the microorganism receives heat stress, strong fabrication of cell walls will be hampered because older peptidoglycan of cell walls will be vulnerably stretched to its breaking point [27]. The decomposed peptidoglycan will be rapidly solubilized by peptidoglycan hydrolases, causing pores on the cell walls.…”

Section: Discussionmentioning

confidence: 99%

Bactericidal effects of diode laser on Streptococcus mutans after irradiation through different thickness of dentin

et al. 2006

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Background and Objectives: A reliable method to eradicate the bacteria of residual carious dentin has not yet been developed. The aim of this study was to evaluate the antibacterial effect of a diode laser on Streptococcus mutans through different thickness (500, 1,000, and 2,000 mm) of human dentin. The thermal effect of laser irradiation was also investigated. Study Design/Materials and Methods: Dentin specimens were inoculated with 2 ml of S. mutans on one side and irradiated by a diode laser on the other side with a power output ranging from 0.5 to 7 W. The laser tip was swept with the whole irradiation area of 7 mmÂ3 mm at a speed of about 10 mm/second with a total irradiation time of 30 seconds. Cooling with distilled water (30 ml/minute) was applied simultaneously during laser irradiation. After laser irradiation, the bacteria was removed from the dentin surfaces and cultured for 48 hours at 378C anaerobically to assess the colony forming units (CFU) per ml. The morphology of the lased bacteria and the temperature rise during laser irradiation were observed by scanning electron microscope (SEM) and measured by thermocouple, respectively. Results: The results revealed that 7 W of laser power could kill 97.7% of CFU through 500 mm thickness of dentin. However, the bactericidal efficiency was significantly reduced as the dentin thickness was increased. The morphological changes of lased bacteria ranged from less affected such as loss of their wall bands and existence of minicells to more severely degenerated, such as disintegration and fusion of cells with pores on the cell wall. Only the dentin specimens with a thickness of 500 mm exhibited a temperature rise greater than 5.58C after receiving 5 or 7 W of laser irradiation. Conclusions: A diode laser can eliminate the Streptococcus mutans of the residual carious dentin without inducing high pulpal temperature rise when the remaining dentin thickness is greater than 1 mm.

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Section: Discussionmentioning

confidence: 99%

Bactericidal effects of diode laser on Streptococcus mutans after irradiation through different thickness of dentin

et al. 2006

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“…Several models have tried to answer the question of how the cell controls the activity of hydrolases during PG synthesis in order to avoid autolysis (24,80,95). Different models have been proposed for gram-positive and gram-negative bacteria, since the former have thick, multilayered cell walls while the latter have essentially a monolayered cell wall (100).…”

Section: Growth Of the Peptidoglycan: Hypothetical Multienzyme Complementioning

confidence: 99%

“…According to the surface stress theory, the wall which is laid down immediately outside the cytoplasmic membrane is in an unextended conformation. As subsequent additions of PG occur, the wall moves outward, becomes stretched, and bears the stress due to hydrostatic pressure (95). Autolytic activity would be expected to be greater in the more stressed (external) layers, since the stress provides a lowering of the reaction activation energy (93,95).…”

Section: Growth Of the Peptidoglycan: Hypothetical Multienzyme Complementioning

confidence: 99%

Bacterial Cell Wall Synthesis: New Insights from Localization Studies

Scheffers

Pinho

2005

Microbiol Mol Biol Rev

532

489

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SUMMARY In order to maintain shape and withstand intracellular pressure, most bacteria are surrounded by a cell wall that consists mainly of the cross-linked polymer peptidoglycan (PG). The importance of PG for the maintenance of bacterial cell shape is underscored by the fact that, for various bacteria, several mutations affecting PG synthesis are associated with cell shape defects. In recent years, the application of fluorescence microscopy to the field of PG synthesis has led to an enormous increase in data on the relationship between cell wall synthesis and bacterial cell shape. First, a novel staining method enabled the visualization of PG precursor incorporation in live cells. Second, penicillin-binding proteins (PBPs), which mediate the final stages of PG synthesis, have been localized in various model organisms by means of immunofluorescence microscopy or green fluorescent protein fusions. In this review, we integrate the knowledge on the last stages of PG synthesis obtained in previous studies with the new data available on localization of PG synthesis and PBPs, in both rod-shaped and coccoid cells. We discuss a model in which, at least for a subset of PBPs, the presence of substrate is a major factor in determining PBP localization.

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“…It is a single, covalently closed molecule, and thus bonds must be broken to generate sites for the insertion of new PG subunits (6). At such sites, penicillin-binding proteins (PBPs) processively elongate glycan strands by adding new subunits to their growing ends (7)(8)(9)(10).…”

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confidence: 99%

Processivity of peptidoglycan synthesis provides a built-in mechanism for the robustness of straight-rod cell morphology

Sliusarenko

Cabeen

Wolgemuth

et al. 2010

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

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The propagation of cell shape across generations is remarkably robust in most bacteria. Even when deformations are acquired, growing cells progressively recover their original shape once the deforming factors are eliminated. For instance, straight-rod-shaped bacteria grow curved when confined to circular microchambers, but straighten in a growth-dependent fashion when released. Bacterial cell shape is maintained by the peptidoglycan (PG) cell wall, a giant macromolecule of glycan strands that are synthesized by processive enzymes and cross-linked by peptide chains. Changes in cell geometry require modifying the PG and therefore depend directly on the molecular-scale properties of PG structure and synthesis. Using a mathematical model we quantify the straightening of curved Caulobacter crescentus cells after disruption of the cell-curving crescentin structure. We observe that cells straighten at a rate that is about half (57%) the cell growth rate. Next we show that in the absence of other effects there exists a mathematical relationship between the rate of cell straightening and the processivity of PG synthesis-the number of subunits incorporated before termination of synthesis. From the measured rate of cell straightening this relationship predicts processivity values that are in good agreement with our estimates from published data. Finally, we consider the possible role of three other mechanisms in cell straightening. We conclude that regardless of the involvement of other factors, intrinsic properties of PG processivity provide a robust mechanism for cell straightening that is hardwired to the cell wall synthesis machinery.cell shape | cell wall | cell curvature | modeling B acteria exhibit a wide variety of shapes, which are precisely maintained over countless generations in most species, though the mechanisms of the process are not well understood. Many bacteria display rod shape, which can confer selective advantages (1). In nature bacteria frequently grow in dense environments such as soil and colonies, and are therefore likely to experience physical constraints. For example, chemotactic rodshaped bacteria are capable of penetrating channels narrower than their diameter to reach nutrient sources. Within the channels, growing and dividing cells undergo significant mechanical stress and acquire various deformed cell shapes (2). Similarly, recent experiments using microchambers showed that external physical forces can cause straight-rod-shaped cells to grow curved (3,4). Once the force is released, cells gradually return to their native straight-rod shape as growth continues (2-4). The properties of cell shape recovery have not received much attention, yet they have important implications for the robust maintenance of cell shape throughout bacterial populations.Here we focus on the straightening of curved rod-shaped cells. Using a mathematical model we show first that straightening of exponentially growing cells is a rather surprising phenomenon that would not occur without a specific mechanism. We then dis...

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Inside-to-outside growth and turnover of the wall of gram-positive rods

Cited by 123 publications

References 28 publications

Bactericidal effects of diode laser on Streptococcus mutans after irradiation through different thickness of dentin

Bactericidal effects of diode laser on Streptococcus mutans after irradiation through different thickness of dentin

Bacterial Cell Wall Synthesis: New Insights from Localization Studies

Processivity of peptidoglycan synthesis provides a built-in mechanism for the robustness of straight-rod cell morphology

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