title: Variation in the genomic locations and sequence conservation of STAR elements among staphylococcal species provides insight into DNA repeat evolution.
abstract: BACKGROUND
  Staphylococcus aureus Repeat (STAR) elements are a type of interspersed intergenic direct repeat. In this study the conservation and variation in these elements was explored by bioinformatic analyses of published staphylococcal genome sequences and through sequencing of specific STAR element loci from a large set of S. aureus isolates.
  
  
  RESULTS
  Using bioinformatic analyses, we found that the STAR elements were located in different genomic loci within each staphylococcal species. There was no correlation between the number of STAR elements in each genome and the evolutionary relatedness of staphylococcal species, however higher levels of repeats were observed in both S. aureus and S. lugdunensis compared to other staphylococcal species. Unexpectedly, sequencing of the internal spacer sequences of individual repeat elements from multiple isolates showed conservation at the sequence level within deep evolutionary lineages of S. aureus. Whilst individual STAR element loci were demonstrated to expand and contract, the sequences associated with each locus were stable and distinct from one another.
  
  
  CONCLUSIONS
  The high degree of lineage and locus-specific conservation of these intergenic repeat regions suggests that STAR elements are maintained due to selective or molecular forces with some of these elements having an important role in cell physiology. The high prevalence in two of the more virulent staphylococcal species is indicative of a potential role for STAR elements in pathogenesis.
authors.affiliation: Department of Genetics, University of Leicester, UK.
authors.forename: Joanne
authors.initials: J
authors.lastname: Purves
authors.forename: Matthew
authors.initials: M
authors.lastname: Blades
authors.forename: Yasrab
authors.initials: Y
authors.lastname: Arafat
authors.forename: Salman A
authors.initials: SA
authors.lastname: Malik
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Bayliss
authors.forename: Julie A
authors.initials: JA
authors.lastname: Morrissey
mesh_terms: D017124:Conserved Sequence; D004269:DNA, Bacterial; D021901:DNA, Intergenic; D019143:Evolution, Molecular; D056426:Genetic Loci; D014644:Genetic Variation; D016680:Genome, Bacterial; D008969:Molecular Sequence Data; D010802:Phylogeny; D012091:Repetitive Sequences, Nucleic Acid; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D013210:Staphylococcus / Q000145:classification / Q000235:genetics* / Q000472:pathogenicity
chemical_list: D004269:DNA, Bacterial; D021901:DNA, Intergenic