Griffith's Transformation Experiment

In 1928, the British bacteriologist Frederick Griffith conducted experiments with two strains of the pneumonia-causing bacterium Streptococcus pneumoniae in mice, one virulent and lethal and the other harmless, and found that mice injected with a mixture of harmless live bacteria and heat-killed virulent bacteria died, with living virulent bacteria later recovered from their bodies. Griffith concluded that some transforming substance had passed from the dead virulent bacteria into the living harmless ones, permanently converting them into the virulent form, a phenomenon he called transformation, though he did not identify the chemical nature of the substance responsible. The experiment supplied the essential starting clue that a later generation of researchers would follow to identify DNA as the material carrying hereditary information.