Transformation of Streptococci

PERRY, DENNIS (Northwestern University Medical School, Chicago, Ill.), AND HUTTON D. SLADE. Effects of filtrates from transformable and nontransformable streptococci on the transformation of streptococci. J. Bacteriol. 91:2216-2222. 1966.-The nature of the transformation competence factor from a group H streptococcus was investigated. The activity of competence factor reached a maximum at the time that optimal competence was attained, the maxima of both occurring in the early log phase of growth. The decrease in competence factor was much more gradual than the decrease in number of competent cells. No inhibitor, however, was detected as being responsible for the decrease in either competent cells or competence factor activity. Efforts to induce transformation in other serological groups of streptococci with the use of group H competence factor were unsuccessful. The development of competence in group H when grown in the presence of nontransformable group A strains resulted in a significant increase in the number of transformants. Culture filtrates from early log phase group A cells also caused an increase in the number of transformants from the group H strain. The addition of 10-4 M ethylenediaminetetraacetic acid to group A (or group H) culture filtrates caused significant increases in the number of transformants. These results thus indicate that group A streptococci, although nontransformable, produce low levels of "competence factor." Late culture filtrates from the group H streptococcus and several strains of group A streptococci possessed deoxyribonuclease-like activity which inhibited the transformation of the group H strain. This activity in the A filtrates, however, was not prevented by group A anti-deoxyribonuclease sera. Instead, these sera also inhibited transformation. Evidence indicates that the lack of transformation of group A streptococci is due to factors other than the production of deoxyribonuclease. The acquisition of transforming ability (competence) by several species of bacteria is accompanied by the production of a substance which is capable of inducing competence in incompetent bacterial cells of the same strain (2, 8, 12). This substance, termed "competence factor" (2), has not been found to be produced by transformable cells in which competence was not allowed to develop or by nontransformable cells. The discovery that competence factor from a transformable group H streptococcus could markedly increase the rate of transformation in 1Public Health Service Research Career Awardee (K6-GM-16284) of the Division of General Medical Sciences, National Institutes of Health. another group H strain (8) led to speculations that perhaps nontransformable streptococci could be rendered transformable. Thus, an investigation into the properties of competence factor and its effect on nontransformable streptococci (9) was performed. Studies of the effect on transformation of culture filtrates from nontransformable streptococci also were undertaken to elucidate the reason for lack of transformation in some strains. MATERIALS AND METHODS Bacterial strains. Group H streptococcus strain Challis, was used as donor and recipient in all transformation experiments. Group A strains T14m and