posted by bebe .
Bacteria Y has a mutation within it’s genome, at gene R, that provides resistance to neomycin. Bacteria Z is sensitive to neomycin, however, when Bacteria Y is placed in a mixture with Bacteria Z, Bacteria Z also gains neomycin resistance.
One cell of Bacterium Y undergoes another mutation at gene R which now provides resistance to neomycin and a closely related anti-biotic, streptomycin. Bacteria Y that has the mutated R gene that gives resistance to both neomycin and streptomycin will be called Y+. When Bacteria Y+ is placed in a mixture with Bacteria Z (that has never been exposed to Bacteria Y before), Bacteria Z does not gain neomycin or streptomycin resistance.
What can explain these results?
Bacteria Y (res to neo) + Bacteria Z (sens to neo) = Bacteria Z (res to neo)
Bacteria Y+(res to neo & strep) + Bacteria Z(sens to neo)=Bacteria Z(sens to neo)
Is it possible that Y contains a plasmid, whereas Y+ a transposon? When the Y+ transposon moves to Z, it locates at a different site?