Bagshaped Macromolecules—A New Outlook on Bacterial Cell Walls

Weidel, Wolfhard; Pelzer, Helmut

doi:10.1002/9780470122716.ch5

Cited by 206 publications

(97 citation statements)

References 135 publications

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“…Because of the curvature, the width L of the segment varies proportionally to 1 − ðr∕RÞ cos ϕ as a function of angular position ϕ along the circumference. Thus, if the rate of PG synthesis initiation k init is a constant per unit surface, then the rate p init of synthesis initiation per unit length measured along the center line of the cell becomes a function of ϕ: p init ðϕÞdϕ ¼ k init 1 − r R cos ϕ rdϕ: [5] Next, we calculate ΔL single ðϕÞ, the average contribution to the cell length of the insertion of a new glycan strand, assuming that synthesis was initiated at some randomly chosen point of the circumference. Without loss of generality we choose this point at ϕ ¼ 0.…”

Section: Methodsmentioning

confidence: 99%

“…The shape of an individual bacterial cell is largely maintained by the peptidoglycan (PG) cell wall, a strong and flexible meshwork of rigid glycan strands and flexible peptide cross-bridges that is under stress from internal hydrostatic (turgor) pressure (5). It is a single, covalently closed molecule, and thus bonds must be broken to generate sites for the insertion of new PG subunits (6).…”

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confidence: 99%

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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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Section: Methodsmentioning

confidence: 99%

mentioning

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 cell-wall is composed of tightly cross-linked peptidoglycan (PG) which encircles the inner membrane and forms a protective layer known as the murein sacculus [1]. The murein sacculus varies in size and chemical content in different species.…”

Section: Introductionmentioning

confidence: 99%

Cell-wall recycling and synthesis in Escherichia coli and Pseudomonas aeruginosa – their role in the development of resistance

Dhar

Kumari

Balasubramanian

et al. 2018

Journal of Medical Microbiology

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The bacterial cell-wall that forms a protective layer over the inner membrane is called the murein sacculus -a tightly crosslinked peptidoglycan mesh unique to bacteria. Cell-wall synthesis and recycling are critical cellular processes essential for cell growth, elongation and division. Both de novo synthesis and recycling involve an array of enzymes across all cellular compartments, namely the outer membrane, periplasm, inner membrane and cytoplasm. Due to the exclusivity of peptidoglycan in the bacterial cell-wall, these players are the target of choice for many antibacterial agents. Our current understanding of cell-wall biochemistry and biogenesis in Gram-negative organisms stems mostly from studies of Escherichia coli. An incomplete knowledge on these processes exists for the opportunistic Gram-negative pathogen, Pseudomonas aeruginosa. In this review, cell-wall synthesis and recycling in the various cellular compartments are compared and contrasted between E. coli and P. aeruginosa. Despite the fact that there is a remarkable similarity of these processes between the two bacterial species, crucial differences alter their resistance to b-lactams, fluoroquinolones and aminoglycosides. One of the common mediators underlying resistance is the amp system whose mechanism of action is closely associated with the cell-wall recycling pathway. The activation of amp genes results in expression of AmpC blactamase through its cognate regulator AmpR which further regulates multi-drug resistance. In addition, other cell-wall recycling enzymes also contribute to antibiotic resistance. This comprehensive summary of the information should spawn new ideas on how to effectively target cell-wall processes to combat the growing resistance to existing antibiotics.

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“…The discovery of PG hydrolases in Escherichia coli paralleled the structural characterization of its cell wall PG (304). Initially, they were elicited by incubating hydrolase-containing cell extracts with PG muropeptides and analyzing the reaction products (198,199).…”

Section: Introductionmentioning

confidence: 99%

Peptidoglycan Hydrolases of Escherichia coli

Heijenoort

2011

Microbiol Mol Biol Rev

187

233

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SUMMARY The review summarizes the abundant information on the 35 identified peptidoglycan (PG) hydrolases of Escherichia coli classified into 12 distinct families, including mainly glycosidases, peptidases, and amidases. An attempt is also made to critically assess their functions in PG maturation, turnover, elongation, septation, and recycling as well as in cell autolysis. There is at least one hydrolytic activity for each bond linking PG components, and most hydrolase genes were identified. Few hydrolases appear to be individually essential. The crystal structures and reaction mechanisms of certain hydrolases having defined functions were investigated. However, our knowledge of the biochemical properties of most hydrolases still remains fragmentary, and that of their cellular functions remains elusive. Owing to redundancy, PG hydrolases far outnumber the enzymes of PG biosynthesis. The presence of the two sets of enzymes acting on the PG bonds raises the question of their functional correlations. It is difficult to understand why E. coli keeps such a large set of PG hydrolases. The subtle differences in substrate specificities between the isoenzymes of each family certainly reflect a variety of as-yet-unidentified physiological functions. Their study will be a far more difficult challenge than that of the steps of the PG biosynthesis pathway.

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Bagshaped Macromolecules—A New Outlook on Bacterial Cell Walls

Cited by 206 publications

References 135 publications

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

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

Cell-wall recycling and synthesis in Escherichia coli and Pseudomonas aeruginosa – their role in the development of resistance

Peptidoglycan Hydrolases of Escherichia coli

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