Genetic Linkage of Mutational Sites Affecting Similar Characters in Pneumococcus and Streptococcus.

Ravin, Arnold W. (University of Rochester, Rochester, N.Y.), and Joscelyn D. H. De Sa. Genetic linkage of mutational sites affecting similar characters in pneumococcus and streptococcus. J. Bacteriol. 87:86-96. 1964.-By interspecific transformation, deoxyribonucleic acid (DNA) determinants conferring resistance to high levels of streptomycin in pneumococcus were found to be allelic with DNA determinants conferring low levels of streptomycin resistance in the Challis and NBSI strains of streptococcus. The reciprocal transformation (low resistance pneumococcus x high resistance streptococcus) led to the same conclusion. In addition, determinants controlling resistance to erythromycin in pneumococcus and the Challis strain of streptococcus were found to become closely linked after interspecific transformation. Modifier genes influencing the phenotype conferred by mutations at the streptomycin-resistance locus differentiate species to a certain extent. The results demonstrate that transformations between pneumococcus and streptococcus are not due to episomes, but involve recombinational events in which genetic material of the host species is replaced by homologous material that performed a similar function in the donor species.