Isolation of a widespread giant virus implicated in cryptophyte bloom collapse

Area of Science:

• Aquatic microbiology
• Freshwater ecology
• Virology

Background:

• Photosynthetic cryptophytes are key freshwater phytoplankton, forming blooms in spring.
• Bloom collapse is attributed to environmental changes and grazing.
• The role of viral infections in terminating freshwater phytoplankton blooms is largely unknown.

Purpose of the Study:

• To investigate the role of viral outbreaks in the collapse of freshwater cryptophyte blooms.
• To isolate and characterize a virus associated with cryptophyte bloom termination.

Main Methods:

• Isolation and characterization of a cryptophyte-infecting virus from a natural freshwater environment.
• Analysis of the virus's phylogenetic placement within abundant freshwater giant virus clades.

Main Results:

• A novel cryptophyte virus was isolated and characterized.
• This virus was identified as a significant factor contributing to the annual collapse of a natural cryptophyte spring bloom.
• The isolated virus represents a clade of abundant giant viruses (phylum Nucleocytoviricota) globally distributed in freshwater ecosystems.

Conclusions:

• Viral lysis is a critical, previously unrecognized factor driving the termination of freshwater phytoplankton blooms.
• Giant viruses, such as the one identified, play a substantial role in regulating freshwater phytoplankton populations.
• This finding highlights the ecological importance of viruses in aquatic ecosystems and their impact on bloom dynamics.