Passage II

Some mutations in Escherichia coli allow the bacteria to survive exposure to an antibiotic. These antibioticresistant bacteria may have a different relative fitness (a measure of survival and reproductive success) than E. coli without mutations. Scientists conducted a study to determine the relative fitness of 5 E. coli strains—1 nonmutated (Strain U) and 4 mutated (Strains W, X, Y, and Z)—when the strains were exposed for 24 hr to each of 5 different concentrations of the antibiotic streptomycin (see Table 1). The effect of the mutation in each of Strains W−Z is listed in Table 2.

Table 1 adapted from Viktória Lázár et al., “Bacterial Evolution of Antibiotic Hypersensitivity.” ©2013 by EMBO and Macmillan Publishers Limited.

11. Consider the mutated strain with an increased rate of cell division. According to Table 1, what was the relative fitness of this strain when it was exposed for 24 hr to a streptomycin concentration of 4 μg/mL ?

Answer and Explanation

Your Answer is

Correct Answer is B

Explanation

According to the title description "mutated strain with an increased rate of cell division" and Table 2, it can be concluded that it is Strain X. Compared with Table 1, when streptomycin concentration is 4, Strain X is 0.1