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Distinct Infection Dynamics and Ecological Success among Closely Related Marine Cyanophages: Why the Differences?

Periodic Reporting for period 3 - PhageDiff (Distinct Infection Dynamics and Ecological Success among Closely Related Marine Cyanophages: Why the Differences?)

Reporting period: 2018-09-01 to 2020-02-29

Viruses are extremely abundant in the oceans and impact the marine ecosystem by influencing the abundance, diversity and evolution of their hosts. However, our understanding of the differences among distinct phylogenetic lineages within a virus family are conspicuously lacking. In this project we are investigating the differences and similarities between clade A and clade B cyanophages from the T7-like virus family that infect the ecologically important primary producing unicellular cyanobacteria belonging to the genera Synechococcus and Prochlorococcus.
We found that clade A phages have a more rapid infection cycle, produce more viral progeny per cycle and are more virulent than the clade B phages. We also found that the clade B cyanophages are more abundant under nearly all of environmental conditions we sampled. Furthermore, clade B phages infect more of the cyanobacteria than the clade A phages in nearly all waters. Therefore, intriguingly, it is the less virulent phage lineage with the slower infection cycle and lower progeny production that is more successful in nature.
These above findings raise the question as to the genetic underpinnings for the differences in infection properties and distribution patterns between these two lineages. To this end we developed a genetic inactivation system for the T7-like cyanophages and have begun to assess the effect on infection of a series of genes that differ between the lineages.
These studies will shed light on the link between genetics, physiology and ecology in this important and abundant group of cyanophages and will shed light as to their impact of cyanophages on the growth and photosynthetic output of unicellular cyanobacteria in the oceans.