MICR 221 Lecture Notes - Lecture 11: Gram-Negative Bacteria, Gram-Positive Bacteria, Escherichia Coli

• School: Queen's University
• Department: Microbiology and Immunology
• Course: MICR 221
• Professor: Eric B Carstens

Document Summary

5-10% of gram negative wall: may be only 1-2 layers thick in gram negative, much more crosslinking in gram positives cell shape maintenance also called murein. Peptidoglycan: nag-nam-nag-nam, linked beta 1,4 connected by short peptides backbone of n-acetyl glucosamine (nag) beta 1,4 linked to n-acetyl muramic acid (nam) Need diamno: one to make peptide chain and one to make crosslink. Chains of linked pg subunits joined by crosslinks (transpeptidation reaction) 1. directly: cooh of terminal alanine to amino group of dap or lysine in next peptide chain. Someg-: 5 gly in a row cross bridge. Braun"s lipoprotein covalently linked to dap: has to be a lot in pg. Peptide linking of third diamino aa, to erminal alanine of neighbour chain. One gigantic molecule cross-linked to each other. 50-60% peptidoglycan up to 50% teichoic acids are proteins but not a significant number no lipid, no lps, no omps (b/c no om) ** techoic acid only links to muramic acid!