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The mechanism of antibiotics

The mechanism of antibiotics. Biol 1220 Synthetic Biology abe pressman & minoo ramanathan. the basics. Used to kill or inhibit the growth of bacteria Classified as bactericidal or bacteriostatic Kill bacteria directly Prevent cell division Classified by target specificity:

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The mechanism of antibiotics

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  1. The mechanism of antibiotics Biol 1220 Synthetic Biology abe pressman & minooramanathan

  2. the basics • Used to kill or inhibit the growth of bacteria • Classified as bactericidal or bacteriostatic Kill bacteria directly Prevent cell division • Classified by target specificity: Narrow-spectrum vs Broad range • Most modified chemically from original compounds found in nature, some isolated and produced from living organisms

  3. sites of antiobiotic action

  4. ampicillin • Belongs to β-lactamgroup of antibiotics – contain β-lactam ring • Broad-spectrum • Penicillin derivative that inhibits bacterial cell wall synthesis (peptidoglycan cross-linking) • Inactivates transpeptidases on the inner surface of the bacterial cell membrane • Bactericidal only to growing E. Coli • Widespread use leads to bacterial resistance. HOW?

  5. ampicillin resistance • Cleavage of β-lactam ring by β-lactamase enzyme

  6. ampicillin resistance • β-lactamase is encoded by the plasmid-linked bla (TEM-1)gene • Hydrolyzes ampicillin • Ampicillin levels in culture continually depleted

  7. use in synthetic biology • To confirm uptake of gene (eg. of plasmids) by bacteria • Bacterial Transformation: DNA integrates into bacteria’s chromosome and made chemically competent • Exogenous DNA tagged with an antibiotic resistance gene eg. β-lactamase • Grown in medium containing ampicillin • Ampicillin resistance indicates successful bacterial transformation

  8. Kanamycin • Targets 30s ribosomal subunit, causing a frameshift in every translation • Bacteriostatic: bacterium is unable to produce any proteins correctly, leading to a halt in growth and eventually cell death

  9. kanamycin use/resistance • Over-use of kanamycin has led to many wild bacteria possessing resistance plasmids • As a result of this (as well as a lot of side effects in humans), kanamycin is widely used for genetic purposes rather than medicinal purposes, especially in transgenic plants • Resistance is often to a family of related antibiotics, and can include antibiotic-degrading enzymes or proteins protecting the 30s subunit

  10. chloramphenicol • Bacteriostatic: functions by halting bacterial growth, which is done by inhibiting the enzyme peptidyl transferase, a protein that assists in the binding of tRNA to the 50s ribosomal subunit • Three methods of resistance: reduced membrane permeability, mutation of the 50s subunit, and an enzyme called chloramphenicol acetyltransferase, which inactivates chloramphenicol by covaltly linking groups • Easy/cheap to manufacture, but unused in western countries because of possible aplastic anemia as a side effect

  11. Sources • http://en.wikipedia.org/wiki/Antibiotic • http://en.wikipedia.org/wiki/Ampicillin • http://en.wikipedia.org/wiki/Beta-lactamase • http://www.sigmaaldrich.com/catalog/ProductDetail.do?N4=A1593|SIAL&N5=SEARCH_CONCAT_PNO|BRAND_KEY&F=SPEC • http://abe.leeward.hawaii.edu/Protocols/QiagenSpinprepProtocol.htm • http://www.openwetware.org/wiki/Brown_BIOL1220:Notebook/SynBio_in_Theory_and_Practice/Bacterial_Basics

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