Loss-Of-Function Mutations in Either Imp or YfgL Genes in Escherichia

Loss-of-function mutations in either imp or yfgL genes in Escherichia coli result in an increased permeability of the outer membrane to small molecules and therefore confer antibiotic sensitivity, as the antibiotics can enter the cell more readily. Interestingly, double mutants, in which both genes are defective, are resistant to antibiotics. Similar to the wild-type strain, but unlike the single mutants, they can grow on media containing antibiotics. This is an example of …

A) synthetic lethality.
B) complementation.
C) synergy.
D) a recessive mutation.
E) None of the above.