How can transformed bacteria that carry genes of interest be identified and isolated...?

Question

...from the majority of non-transformed bacteria?

Answer 1

Bacteria are transformed with plasmids (tiny circles of DNA with a few genes). Foreign genes are spliced into plasmids and the plasmids are taken up by the bacteria. The taking up of plasmids by bacteria is not 100% perfect so one is left with a mixture of cells....cells with the plasmid (and with the foreign gene) and cells w/o the plasmid (w/o the foreign gene). How can one separate these two populations??? If one initially uses a plasmid that has antibiotic resistance and a cell strain that lacks antibiotic resistance, then only transformed cells...bacteria that take up the plasmid with the antibiotic resistance gene will be able to grow on a plate containing the antibiotic. Untransformed cells (those lacking the plasmid with antibiotic resistance gene) will die on a plate containing the antibiotic.