Spontaneously occurring bacterial transformations in mice.

In 1963, it was reported that deoxyribonucleic acid (DNA)-mediated transformations could take place spontaneously between genetically distinguishable pneumococci growing in a living host, the mouse. It was found in the present study that such transformations could be increased in frequency if infected animals were treated with a drug which kills only one of the two infecting strains. The frequency of in vivo transformations was also increased if the infection was prolonged. Interspecific transformation between pneumococci and streptococci without the addition of purified DNA was demonstrated both in vitro and in vivo. These results make it seem more likely that DNA-mediated transformations occur in nature.