A GIANT SINGLE STRANDED DNA VIRUS WITH AN ORIGIN IN DOUBLE STRANDED DNA PHAGE

Single stranded DNA viruses are some of the most successful yet simple pathogens on the planet, found in every environment and infecting organisms from all three domains of life. One of the ocean’s most diverse and abundant primary producers, diatoms, are one of the few known hosts for ssDNA viruses in the ocean. A ssDNA virus was isolated and characterized using the diatoms Pseudo-nitzschia multiseries and Thalassiosira pseudonana. The P. multiseries DNA virus (PmDNAV) has two linear genome segments, 9,682 and 28,403 nt in length, the largest genome of any ssDNA virus. It also has an unusual gene complement for ssDNA viruses including a DNA polymerase B indicating novel replication dynamics for an ssDNA virus. The virus had no homology to previously sequenced ssDNA viruses and instead was more closely related to double stranded DNA viruses and prophage that are integrated into bacterial genomes. The virus indicates that a new type of ssDNA viruses originated from dsDNA viruses. These characteristics suggest that the PmDNAV has a unique lifestyle for ssDNA viruses and represents a new lineage of ssDNA viruses.