Thursday, November 06, 2025 - 1 p.m. to 2 p.m.
Spaulding Hall
Please join us for the DBS Fall Seminar Series
Dr. Nathan Ahlgren - Clark University
November 6th, 2025
1:00PM - 2:00PM in Spaulding G25
Phage-bacteria Dynamics in the Oceans: A Symphony of Cyanophage
Marine cyanobacteria contribute to ~25% of primary production in the oceans. Phages that infect them (cyanophages) exert importance influence on the evolution, physiology, and productivity of their hosts, but we are still understanding the complex relationships that occur between the diverse populations of both. By combining classic phage-host infection assays of isolates and culture-independent analysis of natural communities, we are elucidating the complex interaction network and dynamics of this model phage-host system in the oceans. Analysis of five years of monthly samples from the Pacific reveals a prominent signal of seasonality among diverse cyanophage ‘species’, but also more complex sporadic and persistent patterns. Similar analysis but on a weekly scale in Narragansett Bay, Rhode Island again uncovers highly diverse phage and host communities with remarkable repeated seasonal succession of cyanobacteria host populations, but dampened seasonality in cyanophages. Host-range analysis of over a hundred host and phage isolates from Narragansett Bay uncovers complex patterns of nestedness within broad-scale modularity, but also high prevalence of resistance. These patterns appear to relate to high prevalence of defense genes in the hosts. Taken together, this work indicates that the hundreds to thousands of distinct, co-occurring ‘species’ found in natural populations of cyanobacteria and cyanophage have distinct roles they play, much like members of an orchestra, that collectively produce a complex symphony in the oceans.
