PhytoParasite · Pirsonia-Coscinodiscus as an emerging marine model system for microbial host-parasite interactions

Marine ecosystems are dependent on complex ecological networks. One such network is the ""microbial loop"" which defines global oceans by influencing carbon cycling through the fixation and release of carbon by microorganisms. Although carbon fixation is well understood, factors beyond predation that impact cell death and carbon release remain understudied . Microbial marine parasites can greatly impact carbon release by driving the collapse of massive algal blooms and impacting phytoplankton population sizes. However, our understanding of the mechanisms governing these host-parasite interactions are limited, largely due to a lack of tractable model systems. The PhytoParasite project will address this issue by developing an emerging host–parasite model system comprised of the bloom–forming diatom, Coscinodiscus radiatus, and the zoosporic parasite, Pirsonia diadema, with the goal of answering fundamental questions about the ecological implications, molecular mechanisms, and evolution of phytoplankton parasites. To this end, I will (1) investigate the ecological implications of these parasites by using live–cell fluorescence microscopy to understand the effects of environmental factors on infection dynamics, (2) identify genes involved in parasitism and host responses by performing single–cell RNA sequencing during infection progression, and (3) uncover the mechanisms underlying the parasitic interaction and its evolutionary history using functional experiments and comparative genomics. This work will reveal the ecological implications and genetic underpinning of this important interaction, help develop a framework for understanding the evolution of eukaryotic parasitism, and importantly provide a new model system for understanding microbial interactions in our rapidly changing oceans.""