Scientists used two strains of a bacterium called the S-strain and the R-strain of a bacterium that causes pneumonia. The S-strain caused pneumonia when injected into mice and the R-strain was a safe strain that did not cause pneumonia.The scientists injected the mice separately with the live R-strain (safe form) and dead S-strain (harmful form). In both cases the mice remained healthy.The scientists injected the mice with both forms together. The mice developed pneumonia.Pneumonia is caused by a toxin. The scientists concluded that the information to make the toxin had been passed from the dead S-strain to the living R-strain.When an enzyme that breaks down DNA was added, the dead S-strain was no longer able to transform the R-strain.