Infection of bacterioplankton in the Baltic Sea by lytic and lysogenic viruses

About half of the photosynthetically fixed carbon in the ocean is processed by bacterioplankton. This activity is influenced by viral infection through regulation of bacterioplankton biomass and community composition. The average 10-100 billion viruses per liter seawater infect bacteria and lyse them directly after viral multiplication (lytic viruses) or become incorporated into bacterial genomes (lysogenic viruses). While it is well known today that viruses are abundant, infectious and important in marine waters, detailed information is scarce. It is generally believed that viruses are host-specific and that the production by viruses, and thereby, bacterial mortality, in marine waters is mainly by lytic infection. The evidence for these notions is rather circumstantial, which partly stems from a limited knowledge on I)  lysogenic virus-host systems in natural seawater, and II) the complexity of lytic viral infection. The research projects outlined here are ongoing and preliminary data has been obtained. The projects introduces new approaches to examine aspects of marine lytic and lysogenic viruses in the Baltic Sea. An understanding of virus-host dynamics will contribute to a better understanding of nutrient cycling in the Baltic Sea.

Part 1. Examine host-range and in situ abundance of lysogenic viruses: Phage curing of marine bacterial isolates to examine host-range of lysogenic viruses and the vulnerability of the isolates to viral infection.

Part 2. Determine the complexity of lytic viral infection in a marine virus-host pair. A suite of Cellulophaga baltica strains and their viruses are examined to reveal the complexity of infection patterns in marine plankton.