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Final

study guide for exam

11 Pages
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Department
Biology
Course Code
BIO370Y5
Professor
Tim Westwood

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Cell Structure: Bacterial and Archaeal Cell Envelopes
Action of Antibiotics
Penicillin
Other inhibitors of cell wall synthesis
Antibiotic Resistance
Gram-positive Cell Wall
Teichoic acid
Structure
Cell Walls of the Archaea
Pseudopeptidoglycan
Halococcus & Others
Outer Membrane of Gram-negative Bacteria
Prescott 8th ed: Chapter 3 pages 57-58 and 63-65; Chapter 18 pages 473-477
Degradation of peptidoglycan
A number of enzymes known to cause the decomposition
Lysozyme - Breaks -1,4 glycosidic bonds (product – monosaccharides)
Muramidase - Breaks -1,4 glycosidic bonds (product – disaccharides)
Autolysins - Hydrolyze transpeptide bonds
Penicillin - prevents synthesis of peptidoglycan
Penicillin: General Structure
A -lactam antibiotic
Penicillin
• first discovered by Ernest Duchesne (1896), but discovery lost
• accidentally discovered by Alexander Fleming (1928)
observed penicillin activity on contaminated plate
did not think could be developed further
• effectiveness demonstrated by Florey, Chain, and Heatley (1939)
• Fleming, Florey and Chain received Nobel Prize in 1945 for discovery and production of
penicillin
www.notesolution.com
Figure 34.1
Penicillins- inhibit peptidoglycan synthesis
Penicillinase - enzyme produced by penicillin resistant bacteria
Figure 34.5
Natural & Semi-synthetic Penicillins
Narrow & Broad Spectrum
The -lactam region of the drug resembles the D-Ala-D-Ala end of the peptide to which
the transpeptidase enzyme binds. The structures are shown below.
How does penicillin work to kill bacterial cells ?
Mechanism of Inhibition of PBPs
Much more effective against PBP1A, 1B & 2 than PBP4 !
www.notesolution.com
Susceptibility & Resistance
Some bacteria are not susceptible to penicillin, why?
Penicillin can not get to the site of action Gram-negative bacteria
Narrow spectrum
Cell wall has a different architecture Mycoplasma, Archaea
It is actively exported from the site of action
It is inactivated and/or decomposed
-Lactamase also called penicillinase
Vancomycin
It is a branched tricyclic, glycosylated, nonribosomal peptide produced by the Fermentation of
the Actinobacteria
Vancomycin acts by inhibiting proper cell wall synthesis in Gram-positive bacteria.
Effective against Gram-positive bacteria, such as Streptomyces, Corynebacteria, Listeria,
Bacillus.
Specifically, vancomycin prevents incorporation of N-acetylmuramic acid (NAM)- and N-
acetylglucosamine (NAG)-peptide subunits into the peptidoglycan matrix; which forms
the major structural component of Gram-positive cell walls.
The large hydrophilic molecule is able to form hydrogen bond interactions with the
terminal D-alanyl-D-alanine moieties of the NAM/NAG-peptides.
Normally this is a five-point interaction. This binding of vancomycin to the D-Ala- D-Ala
prevents the incorporation of the NAM/NAG-peptide subunits into the peptidoglycan
matrix. (Wikipedia)
Vancomycin Resistance
Microbial resistance to vancomycin is a growing problem, particularly within health care
facilities such as hospitals.
With vancomycin being the last-line antibiotic for serious Gram-positive infections there
is the growing prospect that resistance will result in a return to the days when fatal
bacterial infections were common.
Vancomycin-resistant enterococci (VRE) emerged in 1987. Vancomycin-resistance
emerged in more common pathogenic organisms during the 1990s and 2000s, including
vancomycin-intermediate Staphylococcus aureus (VISA), vancomycinresistant
Staphylococcus aureus (VRSA), and vancomycin-resistant Clostridium difficile.
www.notesolution.com

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Description
Cell Structure: Bacterial and Archaeal Cell Envelopes Action of Antibiotics Penicillin Other inhibitors of cell wall synthesis Antibiotic Resistance Gram-positive Cell Wall Teichoic acid Structure Cell Walls of the Archaea Pseudopeptidoglycan Halococcus & Others Outer Membrane of Gram-negative Bacteria Prescott 8th ed: Chapter 3 pages 57-58 and 63-65; Chapter 18 pages 473-477 Degradation of peptidoglycan A number of enzymes known to cause the decomposition Lysozyme - Breaks -1,4 glycosidic bonds (product monosaccharides) Muramidase - Breaks -1,4 glycosidic bonds (product disaccharides) Autolysins - Hydrolyze transpeptide bonds Penicillin - prevents synthesis of peptidoglycan Penicillin: General Structure A -lactam antibiotic Penicillin first discovered by Ernest Duchesne (1896), but discovery lost accidentally discovered by Alexander Fleming (1928) observed penicillin activity on contaminated plate did not think could be developed further effectiveness demonstrated by Florey, Chain, and Heatley (1939) Fleming, Florey and Chain received Nobel Prize in 1945 for discovery and production of penicillin www.notesolution.com Figure 34.1 Penicillins- inhibit peptidoglycan synthesis Penicillinase - enzyme produced by penicillin resistant bacteria Figure 34.5 Natural & Semi-synthetic Penicillins Narrow & Broad Spectrum The -lactam region of the drug resembles the D-Ala-D-Ala end of the peptide to which the transpeptidase enzyme binds. The structures are shown below. How does penicillin work to kill bacterial cells ? Mechanism of Inhibition of PBPs Much more effective against PBP1A, 1B & 2 than PBP4 ! www.notesolution.com
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