Genetic exchange and reassignment in .

is considered a keystone pathogen in adult periodontitis but has also been associated with systemic diseases. It has a myriad of virulence factors that differ between strains. Genetic exchange and intracellular genome rearrangements may be responsible for the variability in the virulence of . The present review discusses how the exchange of alleles can convert this bacterium from commensalistic to pathogenic and potentially shapes the host-microbe environment from homeostasis to dysbiosis. It is likely that genotypes of with increased pathogenic adaptations may spread in the human population with features acquired from a common pool of alleles. The exact molecular mechanisms that trigger this exchange are so far unknown but they may be elicited by environmental pressure.