Different bacteriocin activities of Streptococcus mutans reflect distinct phylogenetic lineages

Abstract

Bacteriocins produced by mutans streptococci are known as mutacins. In this study 16 broadly active mutacin-producing Streptococcus mutans strains from New Zealand, North America and Europe were classified into four groups (A-D) on the basis of differences in their activity in deferred antagonism tests against either the homologous producer strain (to test for presence of self-immunity) or indicator strains Staphylococcus aureus 46 and Enterococcus faecium TE1. Two of the strains included in the study (UA140 and UA96) were representatives of the group I and II mutacin producer strains previously described by Caufield and co-workers. One of the New Zealand isolates of group A (S. mutans strain N) appeared to produce inhibitory activity similar to that of the group I prototype strain UA140. Four other New Zealand isolates of group B (S. mutans strains M19, M34, B34 and D14) had mutacin II-like activity. The group B mutacin producers differed from the group A mutacin producers in their additional activity against Staph. aureus 46. Seven S. mutans strains (M46, B46, B57, M12, M28, B28 and 13M) were distinguished from the group A and group B mutacin producers in that they inhibited E. faecium TE1. These were called group C mutacin producers. Strains H7 and H23 resembled the group C strains in their action on both indicator strains TE1 and 46. However, these two strains failed to exhibit immunity to their own inhibitory products in the deferred antagonism test and were separately classified as group D mutacin producers. Phylogenetic analysis of the strains by several genotypic and phenotypic characteristics revealed that the mutacin groups were associated with distinct evolutionary lineages of S. mutans.

Dispensable genes and foreign DNA in Streptococcus mutans

“…It should, however, be noted that the collection of strains studied here was in no way structured, and is restricted to examination of regions of the chromosome known or suspected to be dispensable and subject to variation. It is, therefore, not possible to determine how the regions studied may relate to any clonal structure that might be revealed by examination of the phylogenetic relationships between the strains based on data on housekeeping genes in the core genome, as applied by Balakrishnan et al (2002) in their study of mutacins. The dispensable genome may not reflect the true phylogeny of the core genome or population structure of S. mutans, which can better be explored by multilocus sequence typing (Feil, 2004).…”

Identification of nlmTE , the Locus Encoding the ABC Transport System Required for Export of Nonlantibiotic Mutacins in Streptococcus mutans

“…The inhibitory spectrum of mutacin N is distinctive compared to that of other mutacins in its ability to inhibit certain S. mutans strains (3,4). The resulting nlmT-deficient mutant, N⌬NlmT, failed to express any inhibitory activity ( Table 2), indicating that the NlmTE ABC transporter is also required for nonlantibiotic mutacin export in S. mutans strain N.…”

Frequency of four different mutacin genes in Streptococcus mutans genotypes isolated from caries-free and caries-active individuals

“…Mutacins are peptide or protein antibiotics that are mainly bactericidal for other bacteria of the same or closely related species, as well as for other Gram-positive micro-organisms, and are likely to confer an ecological advantage in diverse bacterial communities such as the dental biofilm (Parrot et al, 1990; Balakrishnan et al, 2002). Some studies have demonstrated that the mutacin activity of S. mutans could be related to the prevalence of this species in the dental biofilm, saliva and dental caries (Berkowitz and Jordan, 1975;Hillman et al, 1987).…”