Isolation and characterization of a novel virus infecting Teleaulax amphioxeia (Cryptophyceae)

Abstract

Teleaulax amphioxeia (Conrad) Hill is a marine free-living cryptophyte. Here, we report the basic characteristics of the cryptophyte-infecting virus “TampV (Teleaulax amphioxeia virus)”, the host of which is T. amphioxeia, as the first such virus to be successfully cultured. TampV strain 301 (TampV301) is a polyhedral large virus (ca. 203 nm in diameter), propagating in its host's cytoplasm. Because of the virion size, thin-section view and propagation characteristics, TampV301 was assumed to harbor a large double-stranded (ds) DNA genome; i.e., TampV is most likely one of the “nucleo-cytoplasmic large DNA viruses (NCLDVs)” belonging to the family Phycodnaviridae. Its infectivity was ‘strain-specific’ rather than ‘species-specific’ as is the case in other algal viruses. The burst size and latent period were roughly estimated to be 430–530 infectious units cell⁻¹ and <24 h, respectively. Considering the uniqueness of cryptophytes' evolutionary position and the host's unique role within the complicated food chain involving kleptoplastid acquisition (composed of T. amphioxeia, the ciliate Myrionecta rubra and a dinoflagellate Dinophysis species), TampV is of much interest from the viewpoints of both eukaryotic host-virus coevolution and marine microbial ecology.