Antibiotics and their mode of action

1. Antibiotics and their mode
of action
Submitted To-: Dr Pooja Sangwan
Submitted by-: Ankush(2019A109M)

2. ANTIBIOTICS
 ANTIBIOTICS : Anti – against & bios – life.
 Antibiotics play key role in managing plant diseases , particularly the
diseases caused by bacteria, mycoplasma, and rickettsia.
 They are most effective means of managing because of their selective
nature.
 Are secondary metabolites produced by microorganisms, which inhibits
the growth of other microorganisms.
 1920- Alexander Flemming discovered Lysozyme in tears.
 1928- Penicillin by Alexander Flemming.
 1944- Streptomycin by Selman Waksman.
 Only Chloramphenicol, Phosphonomycin and Pyrrolnitrin are produced
synthetically.

3. Mode of action
 On the basis of mode of action:
 Inhibition of cell wall synthesis
Damage to cytoplasmic membrane
Inhibition of nucleic acid and protein
synthesis
Inhibition of specific enzyme system

6. Antibiotics, their sources and mode of
action
Beta lactams-:
 includes Penicillin and Cephalosporins
 Penicillin produced by Penicillium sp. And Cephalosporin by
Cephalosporium spp..
 Inhibits murein synthesis; break murein cross-linkage
Macrolides-:
• includes Erythromycin and Carbomysin
• Erythromycin produced by Stryptomyces erythrus and Carbomysin
by S.halstedii
• Inhibits translocation by binding to 50s ribosome

7. Continue…
Aminoglycosides
• includes Streptomycin, Neomycin and Kanamycin
• Streptomycin produced by Streptomyces griseus and binds
to protein S12 of 30s causing aberrant inhibition complex.
• Neomycin produced by S. fradiae and affects 30s ribosomal
subunit and prevents the translocation by misreading of
codon on mRNA.
• Kanamycin produced by S. kanamyceticus and prevent
translocation by misreading of codon on mRNA

8. Continue..
Rifamycins-:
• includes Rifampicin
• Produced by Amycolatopsis rifamycinica
• it inhibits DNA dependent RNA polymerase in bacterial cells by binding
its beta subunit, thus preventing transcription to RNA and subsequent
translation to proteins.
Tetracyclines-:
• includes Chlorotetracycline and Oxytetracycline
• Chlorotetracycline produced by S. aureofaciens and Oxytetracyclines by
S. riomosus
• Inhibits binding of aminoacyl-t-RNA to A site of 30s ribosomes;
Specifically binds to the protein S7 near A site, resulting change in topology.

9. Continue..
Polypeptides-:
• includes Polymixin-G and Bacitracin
• Polymixin produced by Bacilus polymyxa ; destroys cytoplasmic
membrane
• Bacitracin produced by B. subtilis; inhibit murein synthesis
Polyenes-:
• Includes Chloramiphenicol, Amphotericin,Nystatin, Aureofungin,
Pimaricin/Natamycin
• Chloramiphenicol produced by Streptomyces venezuelae and
inhibits peptidyl transferase activity of 50s ribosome; affects
translation step of ribosome(70s) function

10. Continue..
• Amhotercin produced by Streptomyces. nodus ; effective
against eukaryotes ,inactivates membranes containing
sterols(ergosterols) by making pore through which Kions,small
molecules pass
• Nystatin produced by Streptomyces nouresii
• Aureofungin produced by Streptoverticillium cinnamoneus
var terricola
• Pimaricin produced by Streptomyces natalensis
• Nystatin, Aureofungin,Pimaricin inactivates membrane
containing sterols by making pores

11. References
 Plant Bacteriology by Kalyan k. mondal (2011 Kalyani publishers)
 Fundamentals of Plant Bacteriology by Jayshree Jayaraman and Jeevan Prakash
Verma