Abstract
The results of the previous experiment suggested that the antimicrobial activity of bacteriocin (mutacin) produced by Streptococcus mutans strain C3603 (serotype c) must have been reduced in the oral cavity of rats. In order to elucidate the reasons, possible factors to reduce the mutacin activity were examined in vitro. Mutacin killed the S. mutans cells immediately when it came in contact with glucose-grown cells, whereas it did not kill the cells grown in a sucrose-containing medium completely even when mutacin was incubated with the cells for 10 minutes. In addition to this, adsorption of mutacin to the extracellular polysaccharides produced from sucrose by S. mutans was not observed. On the other hand, similar resistance to the mutacin activity by extracellular polysaccharide production was demonstrated in the case of Streptococcus sanguis or Actinomyces viscosus. Furthermore, S. mutans cells grown in a sucross medium supplemented with dextranase induced little resistance to mutacin. The results suggest that the coating of the indicator cells with extracellular polysaccharides must be an important inhibitory factor related to mutacin activity.
