Peptidoglycan structure

gram-negative outer membrane

protects the peptidoglycan sacculus layer from external enzymes like lysozyme.

archaeal pseudopeptidoglycan

The pseudopeptidoglycan repeating subunit is comprised of N acetylglucosamine/NAG and N acetyl alosaminuronic acid joined together with a beta 1-3 glycosidic bond. It is NOT stopped by beta-lactam antibiotics.

peptidoglycan

a polymer comprised of individual glycan strands cross-linked by peptides. The repeating subunit of peptidoglycan is two sugars, N-acetylglucosamine/NAG and muramic acid/NAM linked by a beta 1-4 glycosidic bond. Attached to the NAM sugar is a lactic acid covalently linked to 5 amino acids linked to each other by peptide bonds.

lysozyme

an enzyme secreted by animals (tears, saliva) that can degrade bacterial peptidoglycan

penicillinase

an enzyme that breaks the beta-lactam ring open and renders these compounds unable to inhibit penicillin binding proteins

beta-lactam antibiotics

bind to penicillin binding proteins (PBPs) preventing them from catalyzing peptidoglycan transpeptidation. The binding of beta lactams antibiotics prevents new glycan coils in a growing cell from linking together. Most effective at destroying actively-growing cells, they bind the penicillin binding proteins making it impossible to form a cell wall causing cell lysis due to rupturing their cell membranes

transpeptidation reaction

crosslinks the polysaccharide coils creating a woven peptidoglycan blanket. This can be blocked by beta-lactam antibiotics

teichoic acids

polymers of sugar alcohol phosphates that impart a net negative charge to the outer membrane of Gram positive bacteria and may aid in attachment or immune evasion

multilayer gram-positive peptidoglycan layer

susceptible to degradation by these enzymes