The greedy cyanophage - host vs medium nitrogen sourcing

Viral lysis of microbial hosts releases organic matter; thus, viruses play essential roles in nutrient cycling in marine ecosystems by increasing environmental nutrient availability. Nitrogen (N) is essential for viral replication, which can either be obtained via recycling infected host cell biomass or hijacking host metabolic machinery to acquire N from the environment. The contributions of host-versus-medium derived N for viral protein synthesis is less understood. Waldbauer et al. (2019) applied isotope-labelling and proteomic techniques to explore bacteriophage N sourcing during infection of the cyanobacterium, Synechococcus. 

Biogeochemical models often involve quantitative estimates of virus-mediated recycling of nutrients, where it is assumed that N content of virions released upon lysis cannot exceed the N content of the host. However, the results from this study indicate that the N content of host cells is not a limit on the resources available for phage replication; as ongoing host cell metabolism during infection increases viral productivity through the acquisition of nutrients from the environment via the host. A follow-up from this study could focus on the sourcing of phosphorus for phage protein production during infection, which is also essential for viral replication and could therefore limit phage replication. 

Waldbauer, J. R., Coleman, M. L., Rizzo, A. I., Campbell, K. L., Lotus, J., & Zhang, L. (2019). Nitrogen sourcing during viral infection of marine cyanobacteria. Proceedings of the National Academy of Sciences, 116(31), 15590-15595.