Antibiotic resistance plasmids in bacteria

Molecular biology depends on plasmids for cloning and gene expression.  In order to select for bacteria that contain the plasmids, the plasmids carry drug resistance genes. When bacteria are streaked or spread on a plate containing antibiotic, only the bacteria containing the drug resistance plasmid will be able to grow.
 
LB agar plate containing ampicillin (2 red stripes).
(RIGHT) The E. coli strain DH5a containing the ampicillin resistant pAMP plasmid is able to grow on an agar plate containing ampicillin.
(LEFT) The same strain without the pAMP plasmid cannot grow on the ampicillin plate.
LB agar plate containing kanamycin (1 green stripe).
(RIGHT) The E. coli strain DH5a containing the kanamycin resistant pKAN plasmid is able to grow on an agar plate containing kanamycin.
(LEFT) The same strain without the pKAN plasmid cannot grow on the kanamycin plate.

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