Abstract
Virophages are small double-stranded DNA viruses that are parasites of giant DNA viruses that infect unicellular eukaryotes. Here we identify a novel group of virophages, named Dishui Lake virophages (DSLVs) that were discovered in Dishui Lake (DSL): an artificial freshwater lake in Shanghai, China. Based on PCR and metagenomic analysis, the complete genome of DSLV1 was found to be circular and 28,788 base pairs in length, with a G+C content 43.2%, and 28 predicted open reading frames (ORFs). Fifteen of the DSLV1 ORFs have sequence similarity to known virophages. Two DSLV1 ORFs exhibited sequence similarity to that of prasinoviruses (Phycodnaviridae) and chloroviruses (Phycodnaviridae), respectively, suggesting horizontal gene transfer occurred between these large algal DNA viruses and DSLV1. 46 other virophages-related contigs were also obtained, including six homologous major capsid protein (MCP) gene. Phylogenetic analysis of these MCPs showed that DSLVs are closely related to OLV (Organic Lake virophage) and YSLVs (Yellowstone Lake virophages), especially to YSLV3, except for YSLV7. These results indicate that freshwater ecotopes are the hotbed for discovering novel virophages as well as understanding their diversity and properties.
Highlights
Virophages are small double stranded DNA viruses that act as parasites of giant DNA viruses (La Scola et al, 2008; Fischer and Suttle, 2011; Yau et al, 2011; Gaia et al, 2014)
Samples from five different lakes (Xi Lake, Qiandao Lake, Xuanwu Lake, East Lake, and Dishui Lake) in China were analyzed for virophages by using the major capsid protein (MCP) gene specific primers of eight known virophages (Figure 1, Table 2)
To understand the diversity of virophages in freshwater lakes in China, we performed PCR on samples isolated from five different lakes using virophage MCP genes specific primers
Summary
Virophages are small double stranded DNA (dsDNA) viruses that act as parasites of giant DNA viruses (La Scola et al, 2008; Fischer and Suttle, 2011; Yau et al, 2011; Gaia et al, 2014). The first virophage, Sputnik, was isolated in conjunction with the giant DNA virus mamavirus, a relative of mimivirus, from a water-cooling tower in Paris, France (La Scola et al, 2008). Several other virophages were subsequently identified, including Mavirus, a virophage infecting Cafeteria roenbergensis virus (CroV), and Zamilon, a close relative of Sputnik, which was isolated with the Mimiviridae related virus Mont (Fischer and Suttle, 2011; Gaia et al, 2014). Seven complete genomes of Yellowstone Lake virophages (YSLVs) were assembled from Yellowstone Lake metagenomic datasets
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