Sandbox 128: Difference between revisions

The bacterial cell wall is crucial for maintaining the structural integrity of bacteria and protects bacteria from osmotic stress and toxic compound. The cell wall is composed of peptidoglycan (Figure 2), and in Gram positive bacterial species (e.g. S. aureus) is many layers thick, while in Gram negative bacterial species (e.g. Escherichia coli) is only a few layers thick. The difference in the number of peptidoglycan layers accounts for the differential staining of these two groups of organisms. Peptidoglycan consists of a carbohydrate portion: alternating residues of [http://en.wikipedia.org/wiki/N-Acetylmuramic_acid N-acetylmuramic Acid (NAM)] and [http://en.wikipedia.org/wiki/N-Acetylglucosamine N-acetylglucosamine (NAG)] that polymerize to form long chains, and a protein portion: a pentapeptide chain that terminates with to D-alanines (D-Ala) residues. The pentapeptide chains are covalently bound to each NAM residue. Rows of peptidoglycan are cross-linked together with pentaglycine chains to form a "mesh-like" structure. This cross-linking reaction is catalyzed by TPs.[[Image:Cell Wall 7 30 2013.jpg|thumb|alt= Alt text| Figure 1.(A)Rows of Peptidoglycans forming a Bacterial Cell Wall (B)Peptidoglycan with D-Ala-D-Ala substrate |550px]]