1. 1 Dr. Alvin Fox External layers of vegetative cells and spores, Lecture 27

2. 2 KEY WORDS Cell envelope Teichoic acid Cell wall Teichuronic acid Cell membraneLipoteichoic acid Outer membrane Mycolic acid Peptidoglycan Undecaprenol (bactoprenol) Braun lipoprotein Endospore (spore) Porins Cell division Lipopolysaccharide

3. 3 Topics: Structure of vegetative cell envelopesStructure of vegetative cell envelopes –unique cell envelope molecules –biosynthesis of cell wall constituents Endospores (dormant cells) Endospores (dormant cells) Cell divisionCell division

4. 4 Cell Envelope ell membrane + cell wall (+ plus outer membrane) Cell membrane + cell wall (+ plus outer membrane) Cell wall Cell wall – peptidoglycan – attached structures

5. 5 Bacterial cell envelopes Gram stain (+ or -) correlates with structure

6. 6 Gram positive Gram negative

7. 7 Peptidoglycan single macromolecule single macromolecule highly cross-linked highly cross-linked surrounds cell surrounds cell provides rigidity provides rigidity

8. 8 Peptidoglycan glycan backbone –muramic acid –glucosamine peptide side chain peptide cross-bridge (or direct peptide bond) –D- and L- amino acids – sometimes diaminopimelic acid

9. 9 Muramic acid, D-amino acids diaminopimelic acid – not synthesized by mammals

10. 10 Peptidoglycan Example with direct peptide bond Muramic acid Glucosamine L-alanine D-glutamic acid L-lysine/Diaminopimelic acid D-alanine

11. 11 Gram Positive Cell Envelope Teichoic acid –polymer –ribitol phosphate or ribitol glycerol backbone – Teichuronic acid –polymer –no phosphorus –glucuronic acid

12. 12 Teichoic and teichuronic acids Metal ion uptake Direct autolytic enzymes –holes punched in cell wall –allows insertion cell wall (synthesis)

13. 13 Lipoteichoic acids cell membrane autolysins kept from cell wall

14. 14 Gram Positive Cell Envelope r Lipoteichoic acid Peptidoglycan-teichoic acid Cytoplasmic membrane

15. 15 Braun lipoproteinBraun lipoprotein –binds cell wall to outer membrane Gram Negative Peptidoglycan

16. 16 Outer Membrane lipopolysaccharidelipopolysaccharide phospholipidsphospholipids ProteinsProteins –porins

17. 17 Lipopolysaccharide Lipid A Glucosamine disaccharide Beta hydroxy fatty acids Core Heptoses Ketodeoxyoctonic acid O-antigen Highly variable n

18. 18 Inner (cytoplasmic) membrane Outer Membrane Lipopolysaccharide Porin Braun lipoprotein Gram Negative Cell Envelope Peptidoglycan

19. 19 rrr rr r Acid Fast Cell Envelope rrrr Peptidoglycan-arabinogalactan-mycolic acid Cytoplasmic membrane Mycolic acid lipids

20. 20 Peptidoglycan synthesis Cytoplasm Cell wall undecaprenol sugar aminoacid Cell Membrane 123

21. 21 Lipopolysaccharide synthesis similar to peptidoglycan also on undecaprenol carrier

22. 22 Spore Modified Gram positive bacteria cellModified Gram positive bacteria cell – unusual cell envelope cell membranecell membrane outer membraneouter membrane

23. 23 Spore Peptidoglycan layer Peptidoglycan layer – cortex – between two membranes – less cross-linked – dehydrated muramic acid (lactam)

24. 24 Vegetative cell division Sporulation

25. 25 cortex The endospore exosporium coat Innermembrane outermembrane