MEPS 254:27-35 (2003)  -  doi:10.3354/meps254027

Stable coexistence in marine algal host-virus systems

Runar Thyrhaug1,2,*, Aud Larsen1, T. Frede Thingstad1, Gunnar Bratbak1

1Department of Microbiology, University of Bergen, Jahnebakken 5, Postbox 7800, 5020 Bergen, Norway
2Present address: Nordland Research Institute, 8049 Bodø, Norway

ABSTRACT: 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.


KEY WORDS: Phytoplankton · Marine viruses · Coexistence · Viral ecology


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