Marker discrimination in deoxyribonucleic acid-mediated transformation of various Pneumococcus strains.

The function responsible for discrimination among markers (point mutations) in Pneumococcus (hex) was traced back to the early strains used to demonstrate the chemical basis of transformation in the early 1940s. Those currently used laboratory strains failing to manifest this function arose from a single subline of the original strain. The function was also evident in other independently isolated strains including a number of different serological types. The hex function was not evident in transformation between heterologous pneumococcal strains probably as a result of the sensitivity of the function to saturation in the presence of deoxyribonucleic acid from closely related but nonisogenic strains.