Isolation of a Streptococcus mutans strain producing a novel bacteriocin.

A strain of Streptococcus mutans has been isolated that produces a bacteriocin with novel properties. Its antibiotic spectrum includes 123 of 124 strains of S. mutans tested and a variety of other gram-positive microorganisms. Experiments with dialysis membranes indicate that the molecular weight of the bacteriocin is less than 1,000. Mutants of the producer strain were obtained that are deficient in bacteriocin production or produce twofold elevated amounts. The ability of these strains to superinfect or preemptively colonize the oral cavities of rats correlated with the amount of bacteriocin they produced.