Cyanophage Diversity and Community Structure in Dead Zone Sediments.

Area of Science:

• Marine microbiology
• Viral ecology
• Biogeochemistry

Background:

• Viruses cause significant daily mortality in marine prokaryotes, influencing microbial diversity and biogeochemical cycles.
• Cyanophages, viruses infecting cyanobacteria, release nutrients and carbon, impacting marine ecosystems.
• Cyanobacteria form blooms and are crucial in nitrogen fixation, contributing to oxygen depletion and dead zones.

Purpose of the Study:

• To investigate the diversity and community structure of cyanophages and cyanobacteria in Baltic Sea dead zone sediments.
• To analyze cyanophage and cyanobacteria in relation to oxygen gradients (oxic, hypoxic, anoxic).
• To understand the potential impact of cyanophages on cyanobacterial gene expression and nutrient cycling in dead zones.

Main Methods:

• Sampling of surface sediments along an oxygen gradient in the Baltic Sea.
• DNA and RNA sequencing to identify and analyze cyanophage and cyanobacterial communities.
• Bioinformatic analysis of partial genome contigs and RNA transcripts.

Main Results:

• Cyanophages were detected across all sampled stations.
• Hypoxic-anoxic sediments showed higher cyanophage alpha diversity and distinct beta diversity compared to oxic sediments.
• Detected cyanophages potentially affect cyanobacterial photosystem and phosphate regulation; key genera include Dolichospermum/Anabaena, Synechococcus, and Cyanobium.

Conclusions:

• Dead zone sediments harbor unique cyanophage communities, suggesting environmental selection.
• Cyanophage activity in dead zones may influence cyanobacterial gene expression and nutrient turnover.
• Viral lysis of cyanobacteria likely contributes to high carbon, phosphorus, and nitrogen turnover in anoxic marine environments.