HORIZONTAL GENE-TRANSFER IN THE EVOLUTION OF GROUP-A STREPTOCOCCAL EMM-LIKE GENES - GENE MOSAICS AND VARIATION IN VIR REGULONS

Most M type 5 group A streptococcal strains were found to contain a si ngle emm-like gene between virR and scpA (the Vir regulon), but two di stinct emm-like genes were identified in the Vir regulon of the M5 str ain NCTC8193. The complete sequences of both of these genes were deter mined. One, called emm5.8193, was shown to be a minor variant of the p reviously described emm5 gene from strain Manfredo. The second, design ated enn5.8193, expresses an IgG-binding protein when cloned in Escher ichia coli. A comparison of enn5.8193 with emm-like gene sequences fro m other strains indicated that it has a mosaic structure, consisting o f distinct segments originating from emm-like genes in different OF+ a nd OF- strains. These data provide the first clear evidence that the h orizontal transfer of emm-like sequences between distinct strains cont ributes to the evolution of group A streptococcal emm-like genes and V ir regulons.