GENETIC-VARIABILITY OF THE EMM-RELATED GENES OF THE LARGE VIR REGULONOF GROUP-A STREPTOCOCCI - POTENTIAL INTRAGENOMIC AND INTERGENOMIC RECOMBINATION EVENTS

One of the most prevalent genetic lineages of group A streptococci (GA S) harbors a genomic locus termed the large vir regulon, which contain s an emm gene encoding the antiphagocytic M protein, and structurally related fcr A and enn (emm-related) genes encoding immunoglobulin-bind ing proteins. In the present study more than 100 large vir regulons fr om 42 different GAS serotypes were analyzed by PCR and partial DNA seq uencing. On comparing these data to published sequences, sites of muta tional and putative recombinational events were identified and ordered with respect to their intra/intergenic or intra/intergenomic nature. The emm-related genes were found to display small intragenic deletions or insertions, were completely deleted from, or newly inserted into t he genome, or were fused to adjacent genes. Intergenomic exchanges of complete emm-related genes, or segments thereof, between different vir regulons were detected. Most of these processes seem to involve short flanking direct repeats. Occasionally, the structural changes could b e correlated with changes in the functions of the encoded proteins.