Memory in viral quasispecies

Biological adaptive systems share some common features: variation among the ir constituent elements and continuity of col-e information. Some of them, such as the immune system, are endowed with memory of past events. In this study we provide direct evidence that evolving viral quasispecies possess a molecular memory in the form of minority components that populate their mu tant spectra. The experiments have involved foot and-mouth disease virus po pulations with known evolutionary histories. The composition and behavior o f the viral population in response to a selective constraint were influence d by past evolutionary history in a way that could not be predicted from ex amination of consensus nucleotide sequences of the viral populations. The m olecular memory of the viral quasispecies influenced both the nature and th e intensity of the response of the virus to a selective constraint.