Elements of a theory for the mechanisms controlling abundance, diversity, and biogeochemical role of lytic bacterial viruses in aquatic systems

Mechanisms controlling virus abundance and partitioning of loss of bacteria l production between viral lysis and protozoan predation are discussed with in the framework of an idealized Lotka-Volterra-type model. This combines n onselective protozoan predation with host-selective viral lysis of bacteria . The analysis leads to a reciprocal relationship between bacterial diversi ty and viruses, in which coexistence of competing bacterial species is ensu red by the presence of viruses that "kill the winner," whereas the differen ces in substrate affinity between the coexisting bacterial species determin e viral abundance. The ability of the model to reproduce published observat ions, such as an approximate 1:10 ratio between bacterial and viral abundan ce, and the ability of viral lysis to account for 10-50% of bacterial loss are discussed.