Charfreitag, O. and W.-E. Krumbein
Geomicrobiology, ICBM, Carl von Ossietzky University Oldenburg, P.O.B. 2503, D-26111 Oldenburg, Germany
Cyanobacteria of the genus Synechococcus are important primary producers in the Sea.Viruses can be important to maintain diversity of microbial communities and for mineral cycling. In this study viruses of Synechococcus spp. from the Western Baltic Sea were investigated. Seventeen strains of phycoerythrin-containing Synechococcus were isolated from the Western Baltic Sea . The seasonal abundance of cyanophages infecting two of the strains was investigated in 1995 and 1996. The highest titers of Synechococcus-phages (2,5 x 104 ml-1) were found in September 1996, the lowest (<1 ml-1) in spring and early summer 1996. There was a threshold of about 104 Synechococcus cells ml-1, above which viral propagation was efficient. Several viruses infecting Synechococcus sp. were isolated in 1992/93 and 1995/96. The isolated phages belong to the group of Siphoviridae. At least one morphological type of phage belonging to the Myoviridae was additionally apparent in high concentration. Only one of the Synechococcus-strains was lysed by abundant cyanophages in 1992/93, whereas several Synechococcus-strains were lysed in 1995/96. The isolated viruses were described morphologically and by restriction length analysis.
These results indicate that viruses infecting Synechococcus spp. are an abundant and dynamic component in the Western Baltic Sea. The data emphasize further that they could be an impotant factor to maintain diversity of the Synechococcus population.