Question

^{(c) An E. coli strain was created by transforming with the two plasmids shown below: pm Tet' gene pxyls HOC 5 G. E. coli Amp' gene Kan gene Mutants of this transformed E. coli strain can be obtained by exposing the cells to dimethyl sulfate. Briefly, explain how you might screen these mutants to obtain an xyls variant that can bind to 4-ethylbenzoic acid 1, carefully explaining the logic underlying your protocol. You can assume that wild type xyls cannot bind to 4-ethylbenzoic acid). (6 points)}

Answer 1

After the transformation experiment the mutant E.coli is able to survive in dimethyl sulfate.Therefore to screen the xylS variant amongst them we should make a media containing both dimethyl sulfate and 4-ethyl benzoic acid . and plate the bacterial cells onto it. The perfectly transformed cells having the xylS gene in them will bind to 4-ethylbenzoic acid and survive whereas the non xylS variant woud not bind.It can henceforth be quantified spectrophotometrically.