Lytic viruses infecting a Chlorella-like alga

Area of Science:

• * Microbiology
• * Virology
• * Algology

Background:

• * Viruses infecting eukaryotic algae are crucial components of aquatic ecosystems.
• * The Chlorella-like green alga, strain NC64A, serves as a model host for studying algal viruses.
• * Previous research identified viruses like PBCV-1 that infect this algal strain.

Purpose of the Study:

• * To isolate and characterize novel viruses infecting Chlorella-like green alga (strain NC64A) from various freshwater sources.
• * To compare the genomic and physical properties of newly isolated viruses with known algal viruses.

Main Methods:

• * Isolation of viruses from freshwater samples (Illinois, North Carolina, South Carolina) based on plaque formation on Chlorella-like green alga NC64A.
• * Electron microscopy to determine viral morphology and size.
• * DNA extraction and characterization, including hybridization with PBCV-1 DNA and DNA restriction endonuclease digestion.
• * Classification of viruses into groups based on resistance to restriction enzymes.

Main Results:

• * Isolation of multiple viruses forming plaques on Chlorella-like green alga NC64A.
• * Viruses identified as large polyhedrons (160–190 nm) with double-stranded DNA (dsDNA) genomes of approximately 300 kbp.
• * All isolated viral DNAs hybridized with PBCV-1 DNA, confirming a relationship.
• * Significant genomic variation among isolates, even from the same water source, revealed by DNA restriction digestion.
• * Viruses, including PBCV-1, were categorized into five distinct classes based on their differential resistance to specific DNA restriction endonucleases.
• * The observed variations suggest differences in modified bases within the viral dsDNA genomes.

Conclusions:

• * Freshwater environments harbor diverse viruses infecting Chlorella-like green algae.
• * These viruses share common characteristics with PBCV-1 but exhibit genomic heterogeneity.
• * DNA restriction endonuclease analysis is a valuable tool for differentiating closely related algal viruses and may indicate variations in base modification.