Diverse microviruses circulating in invertebrates within a lake ecosystem

Area of Science:

• Microbiology
• Virology
• Ecology

Background:

• Microviruses (family Microviridae) are abundant single-stranded DNA bacteriophages found in diverse environments.
• Previous research primarily focused on microviruses in vertebrate gut microbiomes, leaving invertebrate-associated microviruses understudied.
• Freshwater ecosystems represent a significant, yet largely unexplored, reservoir for microvirus diversity.

Purpose of the Study:

• To investigate the diversity and distribution of microviruses in invertebrate hosts and associated environmental samples from a freshwater lake.
• To characterize novel microvirus genomes and classify them within existing and proposed microvirus subfamilies.
• To explore potential ecological associations between microviruses and different invertebrate groups and environmental compartments.

Main Methods:

• Analysis of microvirus genomes from various invertebrate taxa (Chironomidae, Gastropoda, Odonata, Sphaeriidae, Unionidae) and environmental samples (water, sediment) using gene-sharing networks.
• Genomic classification of 463 distinct microvirus genomes into established and proposed subfamilies (Gokushovirinae, Pichovirinae, Alpavirinae, Occultatumvirinae/Tainavirinae) and an undefined cluster.
• Principal coordinate analysis to assess associations between microvirus genomes and sample types, including invertebrate groups and environmental compartments.

Main Results:

• Identification and characterization of 463 distinct microvirus genomes, significantly expanding known microvirus diversity.
• Genomic classification revealed dominance of the Gokushovirinae subfamily (382 genomes) and presence in Pichovirinae, Group D, and proposed subfamilies.
• Observed inverse associations between microviruses in benthic sediment and the Odonata group, and correlative associations with 'defended' invertebrates (Gastropoda, Sphaeriidae, Unionidae).

Conclusions:

• This research substantially broadens the known genomic diversity of microviruses, particularly within freshwater invertebrate-associated viromes.
• The study highlights the ecological significance of microviruses in freshwater ecosystems and their varied associations with invertebrate hosts.
• Findings underscore the need for further classification and ecological investigation of these underrepresented bacteriophages.