Ampicillin: Difference between revisions
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Barry Canton (talk | contribs) (Info. about how β-lactamase can consume all the Amp in a batch culture) |
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(would be nice to have a picture of this here) | (would be nice to have a picture of this here) | ||
==Usage Notes== | |||
A 1990 [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=2199796 paper] by [http://www.biology.bnl.gov/cellbio/studier.html Bill Studier] discusses how the secreted [[β-lactamase]] can quickly consume all the ampicillin in a culture (even at 20μg/ml Amp). A stationary culture of ampicillin resistant cells can have such a concentration of [[β-lactamase]] that even a 1/200 to 1/1000 dilution will still contain enough [[β-lactamase]] to consume all the fresh ampicillin before all the non-resistant cells from the stationary phase culture have been killed. | |||
The authors reccommend not allowing cultures to reach stationary phase if you need a high proportion of cells to contain your plasmid. | |||
==References== | ==References== | ||
Molecular Cloning: A Laboratory Manual, Vol 1. | Molecular Cloning: A Laboratory Manual, Vol 1. | ||
Revision as of 12:22, 11 May 2005
Mode of Action
Inhibits the formation of cross-links in the peptidoglycan layer (which prvides rigidity to the cell wall). Most effctive against cells in log phase growth (since this is when new cross-links are being formed), and has little effect on cells in stationary phase.
Mechanism of Resistance
Expression of β-lactamase neutralizes ampicillin. When this enzyme is expressed on a high-copy number plasmid there is significant diffusion into the extracellular medium. As a result non-resistant satellite colonies may form around larger resistant colonies.
(would be nice to have a picture of this here)
Usage Notes
A 1990 paper by Bill Studier discusses how the secreted β-lactamase can quickly consume all the ampicillin in a culture (even at 20μg/ml Amp). A stationary culture of ampicillin resistant cells can have such a concentration of β-lactamase that even a 1/200 to 1/1000 dilution will still contain enough β-lactamase to consume all the fresh ampicillin before all the non-resistant cells from the stationary phase culture have been killed.
The authors reccommend not allowing cultures to reach stationary phase if you need a high proportion of cells to contain your plasmid.
References
Molecular Cloning: A Laboratory Manual, Vol 1.
