In molecular biology, transformation is the genetic alteration of a cell resulting from the uptake, genomic incorporation, and expression of foreign genetic material (DNA). Separate terms are used for genetic alterations resulting from introduction of DNA by viruses ("transduction") or by cell-cell contact between bacteria ("conjugation"). Transformation of cells in tissue culture is usually called transfection.
Transformation was first demonstrated in 1928 by Frederick Griffith, an English bacteriologist searching for a vaccine against bacterial pneumonia. Griffith discovered that a non-virulent strain of Streptococcus pneumoniae could be transformed into a virulent one by exposure to strains of virulent S. pneumoniae that had been killed with heat. In 1944 it was demonstrated that the transforming factor was genetic, when Oswald Avery, Colin MacLeod, and Maclyn McCarty showed gene transfer in S. pneumoniae. Avery, Macleod and McCarty called the uptake and incorporation of DNA by bacteria "transformation." - modified from wikipedia
back to: horizontal gene transfer, HGT
