13 Jan

Bacterial Cell Wall

The bacterial cell wall contains a common and important component called peptidoglycan, which is only found in prokaryotes.  Peptidoglycan is a polymer of alternating n-acetyl-glucosamine (NAG) and n-acetyl-muramic acid (NAM) which are linked by a covalent bond.  Each NAM contains a chain of 4 amino acids.  This amino acid chain crosslinks the adjacent polymers of amino sugars forming a lattice network around the exterior of the cell.  It is this lattice that determines the shape of the cell (coccus, rod, or spiral).  The lattice diversity results from a bridge being formed from different amino acids within the lattice.  For example Staphylococcus may have the serine and glycine amino acid form a bridge as opposed to multimpl glycine residues.  The cell wall of gram positive bacteria is made of up of 90% peptidoglycan.  Most gram positive bacteria have teichoic acid in their cell wall as well.  This is what creates the overall negative charge.