Bacteria can exchange genetic material using transduction, transformation, and conjugation. In a classic experiment by Griffith in 1928, the bacterial species Streptococcus pneumoniae was tested by injecting it into mice.
He found that strains with capsules (“smooth” strains) would cause death in the mice, but that strains lacking capsules (“rough” strains) would not. He treated the smooth strains with heat, killing the cells, and injected them into mice and found that the mice survived.
However, when a mixture of killed smooth cells and live rough cells were injected, the mice died.
It was later discovered that the DNA from the smooth cells was taken up by the rough strain cells, after which these cells incorporated the DNA for the capsule and converting to virulent strains.
This is an example of bacterial