Properties of mutacin b, an antibacterial substance produced by Streptococcus mutans strain BHT.

An antibacterial substance produced by strain BHT of Streptococcus mutans (mutacin b) was found to be a small molecule (MW 3,500-6,000) with remarkable resistance to temperature, alkali and various solvents. Enzyme sensitivity tests of partially purified preparations indicated that mutacin b is a peptide. It is sensitive to several proteolytic enzymes and its lethal effects on sensitive cells can be prevented by adding trypsin to cells exposed to mutacin b. High concentrations of mutacin b inhibited the growth of producer cells, indicating that strain BHT is only partially immune to this substance.