Phase Variation Helps Protect the Bacterium Salmonella Typhimurium Against the Immune

Phase variation helps protect the bacterium Salmonella typhimurium against the immune system of its host by switching the orientation of a certain promoter. This process …

A) is carried out through a DNA transposition mechanism.
B) is irreversible.
C) can often result in the excision of the promoter from the chromosome altogether.
D) is mediated by enzymes that form transient covalent bonds with the DNA.