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Category: Bacterial Pathogenesis
The Staphylococcal Cell Wall, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555816513/9781555813437_Chap36-1.gif /docserver/preview/fulltext/10.1128/9781555816513/9781555813437_Chap36-2.gifAbstract:
The history of interest in the staphylococcal cell wall reflects the history of success and failure of the antibiotic era. Elucidation of the mode of action of several important antibiotics in the 1960s and 1970s has been intimately linked to studies on the biosynthesis of staphylococcal cell walls. In addition to the reemergence of interest in cell walls in the context of modern microbial cell biology, two approaches have been making great impact on discoveries in this field: the introduction of high-resolution analytical techniques (high-pressure liquid chromatography [HPLC] and mass spectrometry) and the increasing application of molecular genetic approaches. This chapter includes a brief reminder of the anatomy of staphylococcal cell walls, and reviews new information under four headings: high-resolution analysis of the Staphylococcus aureus peptidoglycan; variations in peptidoglycan composition; genetic determinants and enzymes in cell wall synthesis; and complex functions of cell walls. Unlike in streptococci, in S. aureus consecutive cell divisions occur in three division planes, each at right angles to one another, and proper orientation of cell wall septa must involve a complex and superbly controlled mechanism. Progress in the high-resolution chemistry of the S. aureus cell wall came from the introduction of HPLC and mass spectrometric methods for the analysis of the peptidoglycan.
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Localization of cell wall synthesis in S. aureus. (A) Van-fluorescence labeling of RN4220 cells. The entire cell wall, including the septum, has been labeled. (B) Van-fluorescence labeling of RN4220 cells after transient incubation with an excess of d-serine. This appears to result in specific labeling of new peptidoglycan. Different stages of septum formation can be observed. Left panel: Cells have two fluorescent spots that presumably correspond to a ring of new peptidoglycan at the division site. Middle panel: Cells have a fluorescent line across the middle, which should correspond to a complete disk of new peptidoglycan—the closed septum. Right panel: A tilted cell allows visualization of an entire ring of new peptidoglycan in an incomplete septum. (C) Wheat germ agglutinin labeling of RN4220 cells, followed by incubation in the absence of the dye. Recently synthesized or uncovered wall material appears as a nonfluorescent region that constitutes the new hemisphere of each daughter cell. (D) Immunofluorescence imaging of PBP2 in RN4220 cells. Scale bars, 1 µm. Phase-contrast microscopy images are shown below each fluorescence image in panels B and C. (Reproduced with permission from reference 65 .)
Localization of cell wall synthesis in S. aureus. (A) Van-fluorescence labeling of RN4220 cells. The entire cell wall, including the septum, has been labeled. (B) Van-fluorescence labeling of RN4220 cells after transient incubation with an excess of d-serine. This appears to result in specific labeling of new peptidoglycan. Different stages of septum formation can be observed. Left panel: Cells have two fluorescent spots that presumably correspond to a ring of new peptidoglycan at the division site. Middle panel: Cells have a fluorescent line across the middle, which should correspond to a complete disk of new peptidoglycan—the closed septum. Right panel: A tilted cell allows visualization of an entire ring of new peptidoglycan in an incomplete septum. (C) Wheat germ agglutinin labeling of RN4220 cells, followed by incubation in the absence of the dye. Recently synthesized or uncovered wall material appears as a nonfluorescent region that constitutes the new hemisphere of each daughter cell. (D) Immunofluorescence imaging of PBP2 in RN4220 cells. Scale bars, 1 µm. Phase-contrast microscopy images are shown below each fluorescence image in panels B and C. (Reproduced with permission from reference 65 .)
The anatomy of cell walls in normal (left) and vancomycin-resistant (right) S. aureus. (Reproduced with permission from reference 81 .)
The anatomy of cell walls in normal (left) and vancomycin-resistant (right) S. aureus. (Reproduced with permission from reference 81 .)
Three-dimensional structure of staphylococcal peptidoglycan. The straight lines of large bowls represent the sugar moieties of the peptidoglycan. Each globe in these lines symbolizes an amino sugar, N-acetylglucosamine (black globe), or N-acetylmuramic acid (white globe). Stempeptides, branching from N-acetylmuramic acid, are characterized by small dark globes with a white center. The connecting interpeptide bridges (pentaglycines) between the stem-peptides are shown as small black globes. Schematic drawing by Peter Giesbrecht, Thomas Kersten, Heiner Maidhof, and Jorg Wecke, Robert-Koch Institute, Berlin, Germany.
Three-dimensional structure of staphylococcal peptidoglycan. The straight lines of large bowls represent the sugar moieties of the peptidoglycan. Each globe in these lines symbolizes an amino sugar, N-acetylglucosamine (black globe), or N-acetylmuramic acid (white globe). Stempeptides, branching from N-acetylmuramic acid, are characterized by small dark globes with a white center. The connecting interpeptide bridges (pentaglycines) between the stem-peptides are shown as small black globes. Schematic drawing by Peter Giesbrecht, Thomas Kersten, Heiner Maidhof, and Jorg Wecke, Robert-Koch Institute, Berlin, Germany.
Analysis of the peptidoglycan of a methicillin-resistant strain of S. aureus (bottom) and its femC mutant (top). (Reproduced with permission from reference 60 .)
Analysis of the peptidoglycan of a methicillin-resistant strain of S. aureus (bottom) and its femC mutant (top). (Reproduced with permission from reference 60 .)
Distribution of glycan chain length in S. aureus. (Top) Tracing of the HPLC profile by UV absorbance. (Bottom) Tracing of the same HPLC chromatogram through radioactivity due to the labeling of the glycan with H3 N-acetylglucosamine. (Reproduced with permission from reference 8 .)
Distribution of glycan chain length in S. aureus. (Top) Tracing of the HPLC profile by UV absorbance. (Bottom) Tracing of the same HPLC chromatogram through radioactivity due to the labeling of the glycan with H3 N-acetylglucosamine. (Reproduced with permission from reference 8 .)
Localization of atl gene products on the cell surface of S. aureus during the division cycle as determined by scanning electron microscopy. Panels a to d show the immunogold labeling patterns on cells at different stages of the cell cycle. Scale bar, 100 nm. (Reproduced with permission from Yamada et al. [ 98 ].)
Localization of atl gene products on the cell surface of S. aureus during the division cycle as determined by scanning electron microscopy. Panels a to d show the immunogold labeling patterns on cells at different stages of the cell cycle. Scale bar, 100 nm. (Reproduced with permission from Yamada et al. [ 98 ].)
Structure of muropeptide components in the methicillin-resistant parental strain and its femC mutant 208 a
a Reproduced with permission from reference 60 .
b ND, not determined.
Structure of muropeptide components in the methicillin-resistant parental strain and its femC mutant 208 a
a Reproduced with permission from reference 60 .
b ND, not determined.