Unstable binary capsulated transformants in pneumococcus.

Through transformation reactions, binary capsulated SI-III strains of pneumococci have been isolated that are unstable and lose the SI capsular genome at high frequency. The instability is caused by the specific mutation in the SIII capsular genome common to all of the unstable strains. In the family of strains studied, the SI capsular genome was integrated into the recipient chromosome in at least two loci: one apparently adjacent to the resident capsular genome and a second some distance from it. A hypothesis is presented to explain the instability of the strains on the basis of redundancy of genetic information.