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Viruses and Algae. By Stephanie Boone. Virus Facts. Most abundant life form in aquatic systems. In the ocean the total number exceeds 10 29. Marine viruses high concentrations up to 10 8 in ml -1 Play a significant role in the transfer of matter and energy in aquatic microbial food webs.

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viruses and algae

Viruses and Algae

By Stephanie Boone

virus facts
Virus Facts
  • Most abundant life form in aquatic systems.
  • In the ocean the total number exceeds 1029.
  • Marine viruses high concentrations up to 10 8 in ml-1
  • Play a significant role in the transfer of matter and energy in aquatic microbial food webs.
  • Infect at least some members of all the major classes of freshwater and marine algae.
    • Reported in at least 44 taxa of eukaryotic algae
    • Includes members 10 of 14 classes of algae
  • Virus Interactions range from
    • true parasitism (chronic infection/cellular release without death)
    • to predation (lytic infection resulting in cell death).
ecological significance
Ecological Significance
  • Play a significant role in the transfer of matter and energy in aquatic microbial food webs.
  • Viral lysis of algae effects carbon nutrient flow.
    • Carbon stored in dissolved organic matter released into system.
    • May influence carbon cycling and climate.
  • Significant role in transfer of information through DNA.
  • Important role in algae blooms.
    • effect marine community structure.
algal viruses
Algal Viruses
  • Despite the established ecological importance of marine viruses there have been few studies which extensively investigate and characterize viruses of algae.
  • The viruses studied extensively fall into two catagories.

Large ds DNA viruses.

PBCV-1, Fsv, EsV

Small viruses.

HaRNA, HaNIV

large dsdna viruses
Large dsDNA Viruses
  • Family Phycodnaviridae
    • Paramecium bursaria chorella virus (PBCV-1) infect eukaryotic unicellular-like green algae.
    • Ectocarpus virus (EsV) Feldmannnia virus (FsV) infect marine brown alga.
  • Common characteristics
    • Found on five continents
    • tropical, subtropical seawater, and freshwater
    • large icosahedral particles 130-190 nm diameter
    • large dsDNA genomes 160-380 kb
    • Viral capsid assembly and DNA packaging occurs in the cytoplasm
pbvc 1 chlorella virus
PBVC-1/ Chlorella virus
  • PBVC-1 infects chlorella algae strain NC64A or Pbi.
  • Chlorella algae are small, spherical, unicellular, nonmotile, asexual reproducing green algae.
  • Hereditary endosymbionts in protozoan P. bursaria - resistant to viral infection when in symbiotic relationship.
  • PBCV-1 - linear nonintegrated genome
    • 16 classes of virus
  • Virus attaches to agal cell wall with hexagonal vertices, digests the wall releases viral DNA into cell.
  • Packaging and assembly of virions takes place in cytoplasm virus released by localized cell wall lysis
esv fsv brown algal viruses
EsV & FsV- Brown algal viruses
  • Ectocarpus virus (EsV) and Feldmannia virus (FsV) infect brown algae
  • densely packed polyhedral viral particles
  • do not infect vegetative cells
  • viral particles displace normal reproductive cells producing sterility
  • Viral capsid assembly and DNA packaging occur in the cytoplasm after nuclear membrane degeneration.
small viruses
Small Viruses
  • Heterosigma akashiwo nuclear inclusion virus (HaNIV) and Heterosigma akashiwo RNA virus (HaRNAV) infect the algae Heterosigma akashiwo (Raphidophyceae) a toxic bloom-forming microalgae
  • Host specific - simultaneous coinfection.
  • HaRNAV 25 nm diameter
    • polyhedral symmetry
  • HaNIV 30 nm diameter
  • replicates to high copy number (105) before host lysis
    • nonenveloped and hexagonal implying icosahedral symmetry.
  • Each virus forms a crystalline array
    • Arrays located in different parts of cell.
slide9

Conclusion:

  • Need more research.
  • We know very very little about the viruses that infect algae.
  • References:
  • Van Etten J L, & Meints R H. Giant viruses infecting algae. Annual Review of Microbiology 1999;53:447-494.
  • Weinbauer M G, & Rassoulzadegan F. Are viruses driving microbial diversification and diversity. Envirnmental Microbiology 2004; 6: 1-11.
  • Lawrence J E. & Chan A M. A novel virus (HaNIV) causes lysis of the toxic bloom-forming alga Heterosigma akashiwo (Raphidophyceae).Journal of Phycology 2001; 37:216-222.
  • Tai V, Lawerence J E, Lang A S, Chan A M, Culley A I, Suttle C A. Characetrization of HaRNAV, a single stranded RNA virus causing lysis of Heterosigma akashiwo (Raphidophyceae). Journal of Phycology 2003; 39: 343-352.