posted by bebe on .
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)
A microbiologist inoculates a growth medium with 150 bacterial cells/ml. If the generation time of the species is 3 hours,
(a) how many generations will it take for the culture to contain more than 9,500 cells/ml? (5 pts.)
(b) how long, in hours, will it be before the culture contains more than 9,500 cells/ml? Show your calculations. (5 pts.) (Points : 10)