Bacteriocinogeny and the properties of some bacteriocins of streptococcus mutans

Of 143 strains of Streptococcus mutans investigated, 98 (70 per cent) were bacteriocinogenic on one or more of a series of indicator strains. The bacteriocins were active not only against other streptococcal species such as Strep. pyogenes, Strep. pneumoniae and enterococci but also against a number of unrelated Gram-positive bacteria. However, the two Gram-negative strains tested were not attacked. Many strains appeared to produce more than one type of bacteriocin and the diversity among these types was evidenced by differences in host-range patterns, sensitivity to heat, chloroform and proteolytic enzymes and, ability to diffuse through membranes. It was clear, however, from an assessment of these characteristics that bacteriocins of both the low and high molecular weight types were produced by various strains of Strep. mutans. On a world-wide basis, strains of serological type c are common and certainly predominate among local isolates. The high incidence of bacteriocinogeny among strains of this serotype, coupled with the fact that most other strains either produced or were sensitive to Strep. mutans bacteriocins, indicated that a bacteriocin typing scheme might be valuable as an epidemiological tool.