GENETIC TRANSFORMATION IN STREPTOCOCCUS SANGUIS

Abstract

The production and the persistence of competence factor (CF) and competence factor inactivator (CFI) of four different strains of Streptococcus sanguis in three media (Todd Hewitt broth, medium II and medium IV) have been examined with respect to kinetics. Both the medium used and the strains examined offered implications on the activities of CF and CFI. CF was not detectable in the culture filtrates of strains Wicky (NCTC 9124) and 445. Strain Blackburn (NCTC 10231) showed activity only in Todd Hewitt broth and strain 14567 in Todd Hewitt broth and medium IV. The activity persisted for 2 to 7 hours during exponential growth. In culture filtrates of the strains Wicky and Blackburn the three media yielded high CFI activity persisting during the entire growth period. The strains 445 and 14567 were less potent CFI producers in medium II and medium IV, and no CFI was detected in the culture filtrates from Todd Hewitt broth. Medium II was the most suitable medium for CFI production and seems appropriate for further studies and isolation of the factor. In medium IV no strain had CF activity. This medium was supplemented with serum, albumin, tyrosine or glutamic acid, and CF and CFI production and persistence by strain 14567 were studied in relation to growth phases. CF and CFI activities were observed in the different supplemented media during short periods of growth, but could not be related to any given phase of growth. The presence of CFI in a culture eliminated or reduced the CF activity, and a specific interaction of CF and CFI was observed. The CFI from the strain Wicky inactivated CF from the strains Challis (NCTC 7868) and Blackburn, but not from the strains 13b and 14567. The CFI from the strains 445 and 14567 reduced the activity of CF produced by the strains 13b and 14567, but not CF from the strains Challis and Blackburn.