To enrich for tyrosine auxotrophs after random mutagenesis, you would place the cells into a medium lacking tyrosine. Why?
Tyrosine auxotrophs can grow without added tyrosine, so they will not be affected by an antibiotic that inhibits cell wall synthesis, while non-auxotrophs will.
Tyrosine auxotrophs can grow without added tyrosine, so you can get the non-auxotrophs to die off this way.
Tyrosine auxotrophs do not grow without external tyrosine, so they will not be affected by an antibiotic that inhibits cell wall synthesis, while non-auxotrophs will.
Tyrosine auxotrophs do not grow without added tyrosine, so they will die off.