No Change, No Life? What We Know about Phase Variation in .

Phase variation (PV) is a well-known phenomenon of high-frequency reversible gene-expression switching. PV arises from genetic and epigenetic mechanisms and confers a range of benefits to bacteria, constituting both an innate immune strategy to infection from bacteriophages as well as an adaptation strategy within an infected host. PV has been well-characterized in numerous bacterial species; however, there is limited direct evidence of PV in the human opportunistic pathogen . This review provides an overview of the mechanisms that generate PV and focuses on earlier and recent findings of PV in , with a brief look at the future of the field.