Bacterial Cell Wall Flashcards
What is Gram - made up of
inner cell membrane
Peptidoglycan
Periplasm
Outer cell membrane
What provides strength to peptidoglycan and why is it useful
Cross linking provided by transferase enzymes
Used for turgidity
What is the peptidoglycan structure?
Glycan chains made of NAG and NAM which are linked to peptide chains (L-ala, D-glutamic acid, DAP, D-ala) although the peptide chains may vary between species
E.g pentoglycine chains in strahyloccocus aureus.
The peptidoglycan subunit is the monomer for its synthesis
How is the peptidoglycan synthesised
- 1st the monomer is made and assembled on lipid carrier molecule like Und-PP and occur in cytoplasm of inner membrane. (monomer is NAM plus 4 aminoacids). with use of enzymes MurA-F - LIPID 1
- Lipid 1 binds to Mray integral membrane protein where NAG - UDP binds to Lipid 1 making the Lipid 2 subunit. which is catalysed by MurG
- FtsW Enzyme causing it to flip membrane.
- This is then incorporated into peptidoglycan by (Glycosyl transferase enzyme) GTase
UDP released and recycled
Gram + is made up of
- inner cell membrane
- peptidoglycan cell wall (thicker then negative)
- cytoplasm
How does cross linking occur in Gran negative bacteria
From DAP to D-ala of adjacent chain peptide bond is formed on D-ala carboxyl group.
How does cross linking occur in Gram positive bacteria
Occurs via interbridge. in Staphylococcus
aureus the interbridge is made up of 5 glycine residues.
Antibiotics that target cell wall synthesis
Vancomyosin
Penicillins
(Beta - lactams) 50% of antibiotics
Penicillins are good against which type of bacteria and why
Gram positive as no membrane present to can block Gtase activity and stop crosslinkages occuring. then lysis occurs
what causes the negative charge in bacteria
Teichoicacid
polymers of glycerol and ribitol and contain phosphates which cause its charge.
