Question

You have an F- cell that contains resistance to Vancomycin on the chromosome and Erythromycin resistance on the plasmid. The F+ cell contains resistance to Tetracycline on the chromosome and Naladixic acid on the plasmid, in addition to the F plasmid. Assuming you may create your own media, which antibiotic(s) would you include in the media if you are trying to ONLY allow for the growth of the recombinant cell?

Answer 1

Given that F- plasmid has resistance to Vancomycin on the chromosome and Erythromycin resistance on the plasmid and F+ cell contains resistance to Tetracycline on the chromosome and Nalidixic acid on the plasmid,
During conjugation, F+ plasmid transfer its genes to the F- plasmid such that after conjugation F- cell become F+ positive. So, F- cell will get the gene for Nalidixic acid resistance. The F- cell will have resistance gene for Nalidixic acid, vancomycin and erythromycin.
So, if we grow the cell in r Nalidixic acid, vancomycin and erythromycin containing media then the recombinant cell will grow.
We cannot sue tetracycline antibiotics as the tetracycline resistance gene is present in bacterial chromosome and bacteria chromosome is not transferred during conjugation between F+ and F-.

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