Frequency of virus-resistant hosts determines experimental community dynamics

Area of Science:

• Aquatic Ecology
• Microbial Ecology
• Evolutionary Biology

Background:

• Bacterial viruses (phages) significantly impact host populations ecologically and evolutionarily.
• Cyanophages influence primary production, nutrient cycling, and planktonic food webs, especially during cyanobacterial blooms.
• The eco-evolutionary consequences of phage resistance in bloom-forming cyanobacteria are understudied.

Purpose of the Study:

• To investigate how varying frequencies of phage-resistant genotypes in Nodularia spumigena affect experimental plankton community dynamics.
• To understand the role of phage resistance in nutrient cycling and community composition under different nitrogen conditions.

Main Methods:

• Established experimental plankton communities with Nodularia spumigena, the cyanophage 2AV2, Chlorella vulgaris, and Brachionus plicatilis.
• Varied initial frequencies of phage-resistant Nodularia genotypes (0%, 5%, 50%) across treatments.
• Cultured communities under nitrogen-limited and nitrogen-rich conditions.

Main Results:

• The frequency of phage-resistant Nodularia genotypes controlled community dynamics.
• High resistance (50%) allowed Nodularia to dominate and retain intracellular nitrogen despite phage presence.
• Low resistance (0%, 5%) resulted in Nodularia lysis, nitrogen transfer to Chlorella and rotifers, and subsequent dominance by Chlorella.

Conclusions:

• Phage resistance evolution in cyanobacteria is a key factor shaping plankton community structure and function.
• Even small phages can exert significant control over aquatic ecosystems through eco-evolutionary feedbacks.
• Understanding phage-resistance dynamics is crucial for predicting the fate of cyanobacterial blooms and associated nutrient cycles.