A healthy cellwallis critical for survival of bacteria.

AB - The 3D structure of the bacterial peptidoglycan, the major constituent of the cell wall, is one of the most important, yet still unsolved, structural problems in biochemistry. The peptidoglycan comprises alternating N-acetylglucosamine (NAG) and N-acetylmuramic disaccharide (NAM) saccharides, the latter of which has a peptide stem. Adjacent peptide stems are cross-linked by the transpeptidase enzymes of cell wall biosynthesis to provide the cell wall polymer with the structural integrity required by the bacterium. The cell wall and its biosynthetic enzymes are targets of antibiotics. The 3D structure of the cell wall has been elusive because of its complexity and the lack of pure samples. Herein we report the 3D solution structure as determined by NMR of the 2-kDa NAG-NAM(pentapeptide)-NAG-NAM(pentapeptide) synthetic fragment of the cell wall. The glycan backbone of this peptidoglycan forms a right-handed helix with a periodicity of three for the NAG-NAM repeat (per turn of the helix). The first two amino acids of the pentapeptide adopt a limited number of conformations. Based on this structure a model for the bacterial cell wall is proposed.

Biosynthesis of the Peptidoglycan of Bacterial Cell Walls

Beveridge T (2006) Visualizing bacterial cell walls and biofilms. Microbe 1: 279–284.

Peptidoglycan structure and biosynthesis - YouTube

Compound 2, in itsvarious peptideforms, is believed to be an important player both in peptidoglycanrecycling events and in an induction event that leads to the expressionof β-lactamase, a key β-lactam antibiotic resistanceenzyme

We are interested in the structural characterization of cell wallremodeling and its implications in antibiotics resistance and virulence.

Peptidoglycan layer is also the structure of bacterial cell wall

Great variation occurs in the composition of the sugars in the Osidechain between species and even strains of Gram-negative bacteria. Atleast20 different sugars are known to occur and many of these sugars arecharacteristicallyunique dideoxyhexoses, which occur in nature only in Gram-negative cellwalls. Variations in sugar content of the O polysaccharide contributetothe wide variety of antigenic types of and and presumably other strains of Gram-negative species. Particularsugarsin the structure, especially the terminal ones, confer immunologicalspecificityof the O antigen, in addition to "smoothness" (colony morphology) ofthestrain. Loss of the O specific region by mutation results in the strainbecoming a "rough" (colony morphology) or R strain.

During homeostasis, includinggrowth, cell wall is simultaneously biosynthesized and degraded.
Single molecule detection of a protein involved in peptidoglycan synthesis

Biosynthesis of the Peptidoglycan of Bacterial Cell Walls XIII

The beta lactam antibiotics are stereochemically related toD-alanyl-D-alanine, which is a substrate for the last step inpeptidoglycan synthesis, the final cross-linking between betweenpeptide side chains. Penicillins bind toand inhibit the carboxypeptidase and transpeptidase enzymes that arerequired for this step in peptidoglycan biosynthesis. Beta lactamantibiotics are bactericidal and require that cells beactively growing in order to exert their toxicity.

Since the cell wall is a unique part ofthe bacteria it becomes very interesting target.

See also Peptidoglycan Cell wall ..

Vollmer W and Höltje JV (2004) The architecture of the murein (peptidoglycan) in gram‐negative bacteria: vertical scaffold or horizontal layer(s)? Journal of Bacteriology 186: 5978–5987.

It forms the cell wall in bacteria surrounding the cytoplasmic membrane.

Biosynthesis of the arabinogalactan-peptidoglycan ..

Glycopeptides, such as the antibiotic vancomycin,inhibit both transglycosylation and transpeptidationreactions during peptidoglycan assembly. They bind to the muropeptidesubunit as it is transferred out of the cell cytoplasm and inhibitsubsequent polymerization reactions. Vancomycin is not effectiveagainst Gram-negative bacteria because it cannot penetrate their outermembrane. However, it has become important in clinical usage fortreatment of infections by strains of that are resistant to virtually all other antibiotics (MRSA).