Intra-species host specificity of HaV (Heterosigma akashiwo virus) clones

Abstract

14 clones of the Heterosigma akashiwo virus (HaV) infecting the harmful bloom causing microalga Heterosigma akashiwo (Raphidophyceae) were isolated from coastal waters of Japan. Host specificities of the virus clones were tested against 18 strains of H. akashiwo isolated from coastal waters of the western part of Japan. Although all of the 14 virus clones lysed 10 of the H. akashiwo strains, in 4 strains no viral lysis was observed with any of the clones. The remaining 4 H. akashiwo strains were lysed by 7 to 11 of the virus clones. Further, viral lysis against H. akashiwo is not always complete, allowing the proliferation of surviving cells. These results indicate 2 possibilities: (1) HaVs are phenotypically diverse in terms of their host specificity; (2) H. akashiwo strains are phenotypically diverse in terms of their viral sensitivity. The high diversity among both the virus clones and the host strains concerning viral infection indicates that the interaction between viruses and hosts in situ appears more complicated than a simple host and pathogen relation.