Gene duplication and amplification events (GDA) have been described to serve as a way to adapt to changing environments. Depending on short nucleotide repeat regions, tandem duplications can arise at low frequency in a RecA dependent fashion. Due to the high homology on DNA level duplicated areas expand and contract in an accordion-like fashion at high frequency. GDAs can mediate e.g. antibiotic resistance by overexpressing minor resistance determinants. Staphylococcal surface anchored molecules possess repeat domains (stalk region) which is needed to display the functional domain of the protein some distance away from the cell surface. The Staphylococcus aureus protein SasG shows tandemly repeated G5 domains interspersed with 50 residue motifs (called E domain) in its B-region. Clinical isolates show plasticity in the number of G5-E domains present in SasG and stalk length variation is associated with phenotypic changes. We anticipate that stalk length variation in Staphylococcal populations is mediated by GDA events and is induced by environmental stresses. Thereby GDAs might induce rapid phenotype switching and niche adaption. This hypothesis is under current investigation.
