Glucosyltransferase (GTF) activity in batch cultures ofStreptococcus sanguisstrain Challis in defined medium was maximum at peak growth and declined rapidly on further incubation into stationary phase. Activity was present in spent culture medium and was associated with 2 polypeptides of approximate Mrs 170 kDa (90% of activity) and 155 kDa (about 10% of activity). Other S. sanguis strains produced similar antigenically‐related polypeptides but with varying activities, and antibodies to theS. sanguisenzyme did not react with enzymes produced by other species of oral streptococci. Increasing the [Na+] reduced GTF production byS. sanguisstrains Challis and NCTC 7865, and byStreptococcus sobrinus, but not byStreptococcus salivarius.Addition of Tween 80 to cultures caused a rapid inhibition of GTF synthesis by strain Challis, but not by strain NCTC 7865. Benzyl alcohol had a slower and less inhibitory effect on GTF production by strain Challis. Tween 80 generally inhibited to varying degrees GTF production by other oral streptococci though inS. sobrinusit was stimulated. The results suggest controls operating on GTF synthesis and secretion by different strains of oral streptococci appear to be divers
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