Associations between picocyanobacterial ecotypes and cyanophage host genes across ocean basins and depth

• Published in: PeerJ
• Main Authors: Clara A. Fuchsman, David Garcia Prieto, Matthew D. Hays, Jacob A. Cram
• Format: Article in Journal/Newspaper
• Language: English
• Published: PeerJ Inc. 2023
• Subjects: Prochlorococcus; Cyanophage; Viral host gene; Virus; Cyanobacteria; Network analysis; Medicine; R; Biology (General); QH301-705.5; Pacific; North Atlantic
• Online Access: https://doi.org/10.7717/peerj.14924; https://doaj.org/article/b04c4375102c4346a124077758de3b35

Background Cyanophages, viruses that infect cyanobacteria, are globally abundant in the ocean’s euphotic zone and are a potentially important cause of mortality for marine picocyanobacteria. Viral host genes are thought to increase viral fitness by either increasing numbers of genes for synthesizing nucleotides for virus replication, or by mitigating direct stresses imposed by the environment. The encoding of host genes in viral genomes through horizontal gene transfer is a form of evolution that links viruses, hosts, and the environment. We previously examined depth profiles of the proportion of cyanophage containing various host genes in the Eastern Tropical North Pacific Oxygen Deficient Zone (ODZ) and at the subtropical North Atlantic (BATS). However, cyanophage host genes have not been previously examined in environmental depth profiles across the oceans. Methodology We examined geographical and depth distributions of picocyanobacterial ecotypes, cyanophage, and their viral-host genes across ocean basins including the North Atlantic, Mediterranean Sea, North Pacific, South Pacific, and Eastern Tropical North and South Pacific ODZs using phylogenetic metagenomic read placement. We determined the proportion of myo and podo-cyanophage containing a range of host genes by comparing to cyanophage single copy core gene terminase (terL). With this large dataset (22 stations), network analysis identified statistical links between 12 of the 14 cyanophage host genes examined here with their picocyanobacteria host ecotypes. Results Picyanobacterial ecotypes, and the composition and proportion of cyanophage host genes, shifted dramatically and predictably with depth. For most of the cyanophage host genes examined here, we found that the composition of host ecotypes predicted the proportion of viral host genes harbored by the cyanophage community. Terminase is too conserved to illuminate the myo-cyanophage community structure. Cyanophage cobS was present in almost all myo-cyanophage and did not vary in proportion with ...