Stable coexistence in marine algal host-virus systems

All microalgal host-virus systems isolated to date are lytic: the viruses lyse the infected hosts within hours after infection. Moreover, current models of phytoplankton host-virus interactions predict rapid extinction of both host and virus. Nevertheless, marine phytoplankton and their respective viruses do coexist in marine ecosystems. To investigate this apparent paradox we performed a series of experiments which show that phytoplankton populations always recover after virus-induced lysis and that endemic viral infections may promote survival of the host population. We hypothesize that phenotypic plasticity of algal susceptibility to viral infection makes such coexistence of host and virus possible.