Previously unknown virus infects marine diatom.

Area of Science:

• Marine Biology
• Virology
• Phycology

Background:

• Diatoms, particularly the genus Chaetoceros, are crucial phytoplankton impacting global oxygen and aquatic nutrition.
• Factors like temperature, salinity, and nutrients traditionally control diatom populations.
• Viral infections represent an underappreciated mortality source for diatoms.

Purpose of the Study:

• To identify and characterize a novel virus infecting the marine diatom Chaetoceros.
• To investigate the characteristics of the Chaetoceros salsugineum nuclear inclusion virus (CsNIV) and its replication within its host.
• To explore the implications of this new host-virus interaction for marine ecological dynamics.

Main Methods:

• Isolation and characterization of CsNIV from infected Chaetoceros salsugineum.
• Electron microscopy to determine viral morphology (38-nm icosahedral structure).
• Genome sequencing and analysis to elucidate the unique ssDNA genome structure and its relation to circoviruses.

Main Results:

• CsNIV replicates in the nucleus of C. salsugineum with a latent period of 12-24 hours and a burst size of 325 infectious units/cell.
• CsNIV possesses a unique partially double-stranded DNA genome, distinct from previously described viruses.
• Sequence analysis revealed a distant relationship to circovirus replicase, suggesting a novel viral lineage.

Conclusions:

• Viral infection is a significant mortality factor for the ecologically important diatom genus Chaetoceros.
• The unique CsNIV genome provides a new system for studying marine virus evolution and host-pathogen interactions.
• The vast diversity of marine plankton suggests the ocean harbors a wealth of undiscovered viruses with ecological significance.