Many Rosetta strains have a plasmid that encode tRNAs for AGG, AGA, AUA, CUA, CCC, GGA rare codons. They are usually on a chloramphenicol-resistant plasmid. Meaning you need both your ampicillin and chloramphenicol in your media. Else your cells are likely to drop the CAmp plasmid and you'll be left with a standard BL21 (DE3) strain.

Though I suggest you check that your in house rosetta strain uses CAmp resistance and not something else as many different rosetta strains exist. Attached table can be helpful.

hi

i agree with stender , you can do following and check various condition :

- E.coli culture in various tube in small volume ( 5 ml ) with difrent antibiotic A- ampicilin (100ug/ml) B- Amp(100ug/ml)+Chl(25ug/ml) C- with out any antibiotic

D-Amp+Tet(10ug/ml)+Str(100ug/ml)

*if cells growth in tube "A" and not growth in tube "B" most probably its not Rosetta ( other strain )

* if cells not growth in tube "A" and growth in tube "C" most probably its a contaminated

* if cells growth in tube "A" and growth in tube "B" most probably its Rosetta

* if cells growth in tube "B" and not growth in tube "C" most probably its Rosetta

* if cells growth in tube "B" and growth in tube "C" most probably its Rosetta gami

With this simple test, you can greatly recognize the E.coli strain.after this stage you could check the expression in small volume (10 ml) with or with out IPTG induction :

< Induce expression of fusion proteins by adding (IPTG) to 0.1 mM final concentration and allow the cells to grow for an additional 3–5 hours at 37c .>

good luck