Microm 410 Fall 2009: Prokaryotic Structure/Function: Part 2/3 Dr. Matt Parsek Peptidoglycan Synthesis Peptidoglycan Synthesis cytoplasm cell membrane cell wall Bactoprenol-P Pi UDP-NAM M G pentapeptide G M Bactoprenol Bactoprenol-P-P P M UMP G P NAM G M pentapeptide M G UDP-NAG Bactoprenol G P NAM‐NAG P NAM-NAG UMP pentapeptide Fig. 6.7a Interbridge peptide Peptidoglycan Synthesis Cross-linking of Peptidoglycan Strands cytoplasm cell membrane cell wall autolysins Bactoprenol-P Pi UDP-NAM Bacitracin M G pentapeptide G D-cycloserine Bactoprenol M (Oxamycin) Bactoprenol-P-P P M UMP G P Transpeptidase (FtsI) NAM G M pentapeptide M G UDP-NAG Bactoprenol G Vancomycin P NAM‐NAG P NAM-NAG pentapeptide UMP Fig. 6.7b pentapeptide Interbridge peptide Microm 410 Fall 2009: Prokaryotic Structure/Function: Part 2/3 Dr. Matt Parsek Cross-linking of Peptidoglycan Strands Antibiotic Resistance autolysins • Inactivate antibiotic β-lactamase (penicillinase) Clavulanic acid β-lactams Augmentin and Trimentin (combination of clavulanic acid and transpeptidase amoxicillin or ampicillin respectively) penicillins and cephalosporins lysozyme • Change chemistry of target site • Limit access of the antibiotic to target site Fig. 6.5 Cell Shape Determination • Modifications made to Peptidoglycan: ‐ lysozyme: Protoplasts/spheroplasts ‐ autolysins Bacillus subtilis ‐ endopeptidase Heliobacter pylori • Protein(s) may play a major role ‐ MreB protein Caulobacter crescentus ‐ MreB has homology to actin, a component of the cytoskeleton of eukaryotes. Shape determining protein‐ crescentin Fig. 6.4 Microm 410 Fall 2009: Prokaryotic Structure/Function: Part 2/3 Dr. Matt Parsek Cell Wall Gram-positive Bacteria intermediate filaments in the bacteria Caulobacter crescentus glycerol similar predicted structures of crescentin and intermediate filaments Fig. 4.20 Cell Wall Gram-negative Bacteria Structures of different Teichoic acids Fig. 4.23 Microm 410 Fall 2009: Prokaryotic Structure/Function: Part 2/3 Dr. Matt Parsek Structure Lipopolysaccharide Outer Cell Wall Proteins • lipoproteins (Braun lipoprotein) Heptose 2-keto-3-deoxyoctonic acid • porins - classical porins (non-specific channels) OmpC- 1.1nm OmpF- 1.2 nm - “specific” porins LamB- maltose and maltodextrins Tsx- uptake of nucleosides Salmonella typhimurium- ~1000 serotypes - “active transport” porin systems Major antigenic determine of Gram‐negative bacteria Uptake of iron chelates, Vit B12, disacharides, and phosphorylated cpds endotoxin Receptors sites for certain phage Fig. 4.22 • OmpA (porin?): is essential to conjugation Archaeal cell walls Polysaccharide cell walls of some Archaea Fig. 4.25 Microm 410 Fall 2009: Prokaryotic Structure/Function: Part 2/3 Dr. Matt Parsek S‐layers as part of the cell wall Capsule and Slime Layer Negative stain with India ink Streptococcus pneumoniae Fig. 4.28 Chemistry of Capsule/Slime Layer Dextran • Polysaccharide in composition Glycocalyx layer Acetobacter xylinum- cellulose capsule (β-1, 4 linkage) Agrobacterium tumefaciens- glycan capsule (β-1, 2 linkage) • Synthesized from sucrose by S. mutans; Crown Gall Tumors involved in plaque formation • Glycoprotein in composition • Polymer can also be used for: • Protein in composition – Antithrombotic agent in microsurgery Bacillus anthracis and Bacillus megaterium – Osmotic agents for treatment of hypovolemia Homopolymer of glutamic acid D-isomer – Lubricant in eye drops • Identifying type of capsule being made: – Size-exclusion chromatography matrix (Sephadex) - chemical analysis E. coli- 50 different serotypes - serotyping Antibodies or immunoglobulins Antigen or an antigenic determinant or epitope Microm 410 Fall 2009: Prokaryotic Structure/Function: Part 2/3 Dr. Matt Parsek Role/Function of Capsule/Slime Layer Slime layer of carbohydrate In the laboratory capsule production can be deemed to be non‑essential. produced by Streptococcus mutans • Attachment or adherence Streptococcus mutans sucrose Dental plaque (109 Bacteria/gram; and over 500 different biofilm species identified) • Protection - desiccation Some bacteria owe their - avoiding phagocytosis pathogenecity to this Dextran structure. Capsule/slime Layer Contributes to Pathogenesis • Streptococcus pyogenes- acute bacterial pharyngitis (sore throat) • Streptococcus pneumoniae- pneumonia • Yersinia pestis- plague • Bacillus anthracis- anthrax • Neisseria meningitidis- meningitis.