A NOVEL VIRUS (HaNIV) CAUSES LYSIS OF THE TOXIC BLOOM-FORMING ALGA HETEROSIGMA AKASHIWO (RAPHIDOPHYCEAE)

Authors

  • Janice E. Lawrence,

    1. Department of Earth & Ocean Sciences (Oceanography), 6270 University Blvd., Vancouver, British Columbia, V6T 1Z4, Canada
    Search for more papers by this author
  • Amy M. Chan,

    1. Department of Earth & Ocean Sciences (Oceanography), 6270 University Blvd., Vancouver, British Columbia, V6T 1Z4, Canada
    Search for more papers by this author
  • Curtis A. Suttle

    1. Departments of Earth & Ocean Sciences (Oceanography), Botany, and Microbiology & Immunology, University of British Columbia, 6270 University Blvd., Vancouver, British Colombia, V6T 1Z4, Canada
    Search for more papers by this author

Abstract

We describe a previously unknown virus that causes lysis of the toxic bloom-forming alga Heterosigma akashiwo (Hada) Hara et Chihara (Raphidophyceae). Heterosigma akashiwo nuclear inclusion virus (HaNIV) does not resemble other algal viruses described to date. HaNIV is small (ca. 30 nm diameter), is assembled in the nucleus, and forms crystalline arrays. We estimate that approximately 105 HaNIV particles are released during lysis of a cell. During a time-course experiment, TEM revealed the first signs of HaNIV infection 24 h after viral addition, and by 74 h 98% of observed cells were visibly infected. The onset of cell lysis, as indicated by a decrease in the relative fluorescence of the cultures, was apparent by 42 h postinfection. The heterochromatin of infected cells is frequently found at the margin of the nucleoplasm, which is consistent with virus-mediated programmed cell death, or apoptosis. HaNIV is clearly different from other described viruses that infect algae, including other viral pathogens of H. akashiwo. These results indicate that viruses other than Phycodnaviridae are pathogens and cause mortality of microalgae in marine systems. It is likely that HaNIV plays an integral role in the population dynamics of H. akashiwo.

Ancillary