Raw sewage harbors diverse viral populations

Area of Science:

• Virology
• Metagenomics
• Environmental Microbiology

Background:

• Current virology focuses on a limited number of culturable or pathogenic viruses.
• Understanding viral universe size and genome diversity is crucial for pathogen emergence and gene exchange studies.
• Untreated wastewater is an ideal environment for assessing viral diversity due to concentrated virions and diverse hosts.

Purpose of the Study:

• To explore viral diversity in nature using deep sequencing of raw sewage.
• To characterize the viral metagenome of untreated wastewater.
• To assess the extent of known and novel viral diversity in this environment.

Main Methods:

• Enrichment of virion populations from raw sewage.
• Deep sequencing of viral nucleic acids.
• Bioinformatic analysis to identify known and novel viral sequences.

Main Results:

• Identification of 234 known viruses, including 17 human viruses, alongside plant, insect, algal viruses, and bacteriophages.
• Discovery of novel viruses across 51 families, establishing untreated wastewater as the most diverse viral metagenome studied.
• The majority of sequence reads showed no relation to known viruses, indicating vast uncharacterized viral diversity.

Conclusions:

• Untreated wastewater harbors an exceptionally diverse viral community, far exceeding current knowledge.
• The majority of Earth's viruses are yet to be characterized.
• Raw sewage is a critical resource for novel virus discovery and understanding viral diversity.