Which of the following events is MOST likely to be due to bacterial conjugation?

  •  An encapsulated strain of Streptococcus pneumoniae acquires the gene for capsule formation from an extract of DNA from another encapsulated strain.
  •  A gene encoding resistance to gentamicin in the Escherichia coli chromosome appears in the genome of a bacteriophage that has infected E. coli.
  •  A strain of Pseudomonas aeruginosa produces β-lactamase encoded by a plasmid similar to a plasmid of another gram-negative organism.
  •  A strain of Corynebacterium diphtheriae produces a toxin encoded by a prophage.