Dynamics of Baltic Sea phages driven by environmental changes

Area of Science:

• Marine microbiology
• Virology
• Ecology

Background:

• Phage predation is a key driver of bacterial mortality in aquatic ecosystems, influencing nutrient cycling and microbial community structure.
• Understanding temporal phage population dynamics is crucial for deciphering their role in microbial succession.

Purpose of the Study:

• To investigate temporal changes in phage diversity and abundance infecting specific bacterial hosts.
• To characterize novel phages and their genomic features.
• To assess phage influence on bacterial succession in a Baltic Sea mesocosm experiment.

Main Methods:

• Isolation of 121 phage strains infecting three bacterial hosts.
• Genome analysis of isolated phages.
• Mesocosm experiment with nutrient amendments.
• Monitoring phage abundance in relation to phytoplankton blooms and bacterial hosts.

Main Results:

• Discovery of a novel Flavobacterium phage genus with unique gene sets for nucleotide modification and cell surface glycosylation.
• Identification of another novel phage genus exhibiting stable microdiversity across experimental conditions.
• Phages infecting Rheinheimera showed high genomic consistency.
• Phage populations peaked post-phytoplankton bloom, correlating with summer months in the Baltic Proper.

Conclusions:

• Novel phage diversity exists in marine environments, with some lineages showing remarkable genomic stability.
• Phages play a significant role in the succession of heterotrophic bacteria, particularly those associated with phytoplankton blooms.
• These findings enhance our understanding of phage-host interactions and their ecological impact in aquatic systems.