This document summarizes antibiotic classification based on their chemical nature and mode of action. It discusses several classes of antibiotics including those that inhibit cell wall synthesis like penicillin, those that inhibit protein synthesis by targeting the 30S or 50S ribosomal subunits, those that inhibit nucleic acid synthesis by targeting RNA polymerase or DNA gyrase, and those that disrupt bacterial membranes. It also describes some specific antibiotics from each class and their mechanisms of action, such as how macrolides like erythromycin inhibit protein synthesis by binding to the 50S ribosomal subunit.

1. Antibiotic classification based on
chemical nature and mode of action
II M.Sc MICROBIOLOGY
18PY04

2. ANTIBIOTIC:
Antibiotic are substance produced
by microorganisms which suppress the
growth / destroy the microorganism. The
antibiotics are derives from not only a
bacteria and fungi.

3. Antibiotic classification based on mode of
action:
cell wall synthesis inhibition
protein synthesis inhibition.
Nucleic acid synthesis inhibition.
Folate synthesis inhibition.
Membrane disruption.

4. Cell wall synthesis inhibition:

6. Examples of bacterial cell wall synthesis
inhibition:
Penicillin
Cephalosporin
Vancomycin
Carbapenems
Beta lactamase.

7. Penicillin:
The bacterial cell wall composed of layers of
peptidoglycan, which is made up of repeating unit N-
acetyl glucosamine (NAG) and N-acetyl muramic
acid (NAM) the NAG and NAM molecules are cross
linked with the activity of transglycolase and
transpeptidase. The result is that the cell wall is not
properly cross-linked

9. Pencillin
binds to the PBP and inactivate on the cell wall
inhibit the transpeptidase
prevent peptidoglycan synthesis
cell wall deficient forms
autolysis
cell death

12. Protein synthesis inhibition:
Protein are important to all living cells. In
protein synthesis takes place in cytoplasm. Proteins
are assembled at a ribosome. In bacterial ribosome
which contain 70S is composed of two parts a small
30S subunit and 50S subunit. Each subunit contain
ribosomal RNA and proteins. Ribosome contains A
and P site.

13. Some antibiotic binds to the both site which
blocks the translocation and peptide bond
formation. Many antibiotics act at different
sites on the bacterial ribosomes to inhibit
protein synthesis.
Inhibition in 30S subunit:
for ex, spectinomycin, aminoglycosides,
kanamycin, streptomycin and tetracycline all
target the 30S subunit of the ribosome.

14. Inhibition in 30S subunit:
In 1st step ribosome binds to the mRNA
then charged tRNA must be placed into the P site of
the ribosome.
Ex, aminoglycosides
Aminoglycosides inhibit the protein synthesis by
binding with high affinity to the A site on the 16S
ribosomal RNA of the 30S ribosome as a result of
this interaction the antibiotic promotes mistranslation
by inducing codon misreading on delivery of the
aminoacyl tRNA

16. Inhibition in 50S subunit:
clindamycin, chloramphenicol, erythromycin,
clarithromycin, linezolid all are target to the
inhibition of 50 S subunit.

17. Inhibition in 50S subunit:
ex, Macrolides are protein synthesis inhibitors.
Its inhibit ribosomal translation.
Macrolides binds To 50S subunit of ribosome
inhibit polypeptide chain elongation and protein
synthesis inhibition
as a result in inhibition of growth and multiplication

20. Nucleic acid synthesis inhibition:
inhibition in RNA synthesis:
the antibiotiocs bind to RNA dependent RNA
polymerase and inhibit the initiation of RNA
synthesis. Ex, rifampin and rifamycin
inhibition in DNA synthesis:
these antibiotics binds to A subunit of DNA gyrase
and prevent supercoiling of DNA thereby inhibiting
DNA synthesis. Ex, quinolones and fluroquinolones.

22. Folic acid synthesis inhibition:

23. Membrane distribution:
The plasma membrane in bacteria is involved
with membrane transport, DNA replication, the
production of ATP.
some antibiotics are blocks this properties such as
polymyxin, daptomycin, telavancin

25. Antibiotic classification based on chemical nature:

30. The presence of macrocyclic lactone ring connected
with one or several carbohydrate residues such as
amino sugars ex., erythromycin, methymycin

31. 2

32. Aminoglycosides these
compounds containing glycoside
bonds in their molecule ex,
streptomycin, gentamycin.

34. Polypeptide antibiotics are a chemically diverse class
of anti-infective and antitumor antibiotics containing
non-protein polypeptide chains.
Examples of this class include actinomycin,
bacitracin, colistin, and polymyxin B. Actinomycin-D

35. bacteriacin
polymyxin

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