Lake Kinneret is the largest natural source of fresh water in Israel. Lake cyanobacteria are composed of both unicellular and filamentous types and have predictable seasonal dynamics. However, no information exists about their cyanophages nor how they affect cyanobacterial dynamics. In order to begin assessing the role of cyanophages in this system, we isolated and characterized cyanophages infecting both unicellular and filamentous cyanobacteria and assessed their abundances over the year. The morphology of a phage infecting unicellular Synechococcus spp. was that of a cyanomyovirus with an icosahedral capsid and a contractile tail. The genome of this phage was 180 kb long with 220 open reading frames (ORFs). It contains structural and DNA replication genes homologous to T4 and thus belongs to the T4-like cyanophage family. Moreover, similar to marine cyanophages, it has bacterial-like genes such as the photosystem II D1 protein and a high light inducible protein. A phage that infects Cylindrospermopsis raciborskii had an icosahedral capsid and short tail. The C. raciborskii phage genome is 95 kb long and contains 107 ORFs. It has very few recognizable replication and structural genes and no photosynthesis genes. In order to assess the abundance of these cyanophages in Lake Kinneret we used genomic information to design specific quantitative PCR primers. This showed that the abundance of the C. raciborskii phage changed over the year with low concentrations in winter and higher abundances during the spring and summer. This work provides the first insight into cyanophages and their dynamics in Lake Kinneret.
