試題詳解

5. Humans have harmless E. coli strains that reside in the intestines. O157:H7 is an E. coli strain reported to cause several food poisoning deaths. Evidence suggests that the virulence of O157:H7 is caused by genes from a virus that infects bacteria. Considering this evidence, which of the following statements most likely explains how the O157:H7 population acquired the genetic variation that distinguishes it from the harmless E. coli strains?
(A) The virus entered the bacterial cell, allowing the bacteria's cellular machinery to create new viruses.
(B) Viral envelope proteins bound receptors on the bacteria, allowing the viral genetic material to enter the cytoplasm and be translated into proteins that increased that bacterium's virulence.
(C) The virus entered the cell and reassorted to acquire specific genes from the bacteria to increase the virulence of the virus.
(D) The virus infected the bacterium, and the bacterial population replicated with a copy of the phage genome in each new bacterium.