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Molecular population genetic analysis of the enn subdivision of group A streptococcal emm ‐like genes: horizontal gene transfer and restricted variation among enn genes
Author(s) -
Whatmore Adrian M.,
Kapur Vivek,
Musser James M.,
Kehoe Michael A.
Publication year - 1995
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1995.tb02279.x
Subject(s) - biology , regulon , locus (genetics) , genetics , gene , horizontal gene transfer , population , streptococcus pyogenes , genome , escherichia coli , bacteria , demography , sociology , staphylococcus aureus
Summary The group A streptococcal emm ‐like genes, which encode the cell‐surface M and M‐like proteins, are divided into distinct mrp, emm and enn subdivisions and are clustered together in a region of the chromosome called the vir regulon. In order to understand the mechanisms involved in the evolution of emm ‐like genes, a 180bp fragment of the 5 variable region of the enn gene was characterized in 31 strains for which emm sequences and multilocus enzyme electrophoretic profiles have been previously determined. The results demonstrate that nucleotide polymorphisms at the enn locus are generated predominantly by point mutations and short deletions or insertions, and that variation among enn and emm genes has arisen by similar mechanisms. However, diversity at the enn locus is restricted in comparison to the emm locus. Moreover, there is strong evidence for intragenic recombination at the enn locus and the pattern of distribution of emm and enn alleles among strains suggests that these genes may be independently acquired by horizontal transfer and recombination from distinct donor strains, thereby generating a mosaic structure for the vir regulon. The results add to a growing body of evidence that horizontal gene transfer has played a major role in the evolution of Streptococcus pyogenes vir regulons.