Effect of Bacteriocin Production by Streptococcus mutans on the Plaque of Gnotobiotic Rats

Abstract

The effect of bacteriocins produced by strains of Streptococcus mutans on the microbial composition of dental plaque was studied in gnotobiotic rats. In one set of tests, using S. mutans strains T2 and SW31, rats were simultaneously infected with the bacteriocinogenic parent (bac') and corresponding bacmutants, and the relative proportions of each strain present in three different tooth sites were determined at various time intervals after inoculation. Some animals were monoinfected with bac' and bac-strains, and in vivo properties, such as plaque fermentation end products, amount of plaque formed, and cariogenicity, were measured. In another series of tests with strains T2 bac' and T2 bac-, animals were sequentially inoculated with a time interval of 1 week. On simultaneous inoculation, the bac-mutant, which was sensitive in vitro to the bacteriocin produced by the parent, was totally unable to establish in a plaque consisting of the bac' strain even when the challenging dose was increased 100-fold. In contrast, the bac' strain was successful not only in invading an established bac-plaque but also in eventually almost eliminating the mutant. In monoinfected animals, there were no significant differences in plaque-forming ability, fermentation end products, or cariogenicity between the two strains. Also, bacteriocin activity was detected in plaque harboring the bac' but not the bac-strain. The results not only indicate that bacteriocin activity can occur in vivo but also suggest that bacteriocinogeny might confer an ecological advantage upon a strain attempting to establish itself in an ecosystem. LITERATURE CITED

Production, purification, and properties of a bacteriocin from Staphylococcus aureus isolated from saliva

“…Howevet, Aly et al (1) and Shinefield et al (30) demonstrated that a certain strain of S. aureus controls outbreaks of staphylococcal infection in nurseries and treats patients with recurrent staphylococcal fumculosis. Furthermore, since bacteriocins produced by oral bacteria are thought to play an important role in the establishment of the ecosystem (24,33), it may be possible that the bacteriocin presented here is responsible for a part of the control mechanism of microbial ecology.…”

Dental plaque biofilms: communities, conflict and control

“…Antagonistic interactions involve the production of inhibitory compounds (bacteriocins, acids, H 2 O 2 , etc.) to inhibit neighbouring cells, and can provide the producer cells with a competitive advantage (120). This might explain, in part, why some bacteria appear in plaque biofilms as discrete clusters of cells ( Fig.…”

Genetic transformation of putative cariogenic properties in Streptococcus mutans

“…Cariogenic strains of S. mutans possess the ability to tenaciously colonize smooth surfaces, a property which is primarily dependent on the synthesis of insoluble glucan mediated by glucosyltransferase (GTF) (10). Many of these strains produce bacteriocins, and it is possible that these antibacterial substances may also play a role in colonization (13). The present study describes the transformation of several potential caries-associated properties to mutant strains with chromosomal DNA from cariogenic S. mutans Furthermore, conditions resulting in enhanced frequencies of transformation of this strain are also described.…”