Iron limitation differentially affects viral replication in key marine microbes

Area of Science:

• Marine microbiology
• Virology
• Biogeochemical cycles

Background:

• Viral lysis is a major driver of microbial mortality in marine ecosystems.
• Iron (Fe) is an essential micronutrient limiting phytoplankton productivity.
• The interplay between microbial iron nutrition and viral lysis dynamics is poorly understood.

Purpose of the Study:

• To investigate how iron availability influences viral infection dynamics in key marine picoplankton.
• To compare the effects of iron limitation on viruses infecting different host types: eukaryotic algae, cyanobacteria, and heterotrophic bacteria.

Main Methods:

• Culturing of marine picoplankton isolates (Ostreococcus, Synechococcus, Vibrio) under iron-limited and iron-replete conditions.
• Monitoring viral infection parameters including latent period and burst size.
• Analyzing viral replication efficiency in relation to host iron status.

Main Results:

• Iron limitation slowed Ostreococcus growth and reduced viral burst sizes, consistent with reliance on host metabolism.
• One Vibrio isolate showed altered viral dynamics (longer latent period, smaller burst size) under iron limitation.
• Another Vibrio isolate and its virus, as well as Synechococcus and its infecting cyanophages, showed no significant impact of iron limitation on viral replication.
• Cyanophages demonstrated efficient replication despite host iron limitation.

Conclusions:

• Viral replication strategies vary significantly in response to host iron availability.
• Certain marine viruses, notably cyanophages, can maintain high replication rates independently of host iron status.
• These findings have implications for understanding microbial population dynamics and carbon cycling in iron-limited oceans.