R-061. Biogeography of Sulfolobus islandicus Viruses
Biogeographic patterns have recently been observed in microbial species however, whether biogeographic patterns exist in viruses is currently under debate. This is important because mobile genes ride on viruses and other genetic elements and can become part of the host genome during infection and integration. Here we explore the biogeography of viruses from geothermal hot springs using signatures of viral interactions found in the genomes of seven fully sequenced Sulfolobus islandicus strains from three geographically isolated populations found in Lassen National Park, Yellowstone National Park, and the Mutnovsky Volcano in Kamchatka, Russia. First, we identify provirus elements of the Sulfolobus spindle-shaped virus (SSV) and compare them to five published SSV sequences. Using MCL clustering, which clusters genes based on sequence similarity score from amino acid BLAST, we grouped all of the viral genes into two categories: those found in every virus (core) and those not found in every virus (variable). Of 80 gene clusters there are seven core gene clusters and 73 variable gene clusters, 39 of which are unique to a single virus. A parsimony tree from a concatenated alignment of the seven core genes from nine total viruses shows a biogeographic structure. Second, we show that CRISPRs (clustered regularly interspaced short palindromic repeats) can be used as a tool to identify signals of biogeography in host, virus, and the interaction between the two. The seven genomes contain a total of 18 CRISPR loci and 1208 spacers, 205 of which match a database sequence. 61% of the matches are to viruses and 10% of the matches are to plasmids. A sequence comparison of spacer hits to sequenced and integrated viruses shows a biogeographic pattern in recent interaction between viruses and S. islandicus. We also show that these sequences can be used to identify seven new viruses integrated into S. islandicus genomes. Sulfolobus viruses show biogeographic patterns in both sequence and interaction with their host.