In marine ecosystems, viruses are 15-fold more abundant than bacteria and archaea, which constitute more than 90% of the living biomass in the oceans. By killing ~20% of bacteria and archaea per day, viruses shape the marine microbial population dynamics and control the global geochemical cycles. As the most abundant photosynthetic organisms on Earth, the unicellular cyanobacteria Prochlorococcus and Synechococcus are responsible for as much as 50% of carbon fixation in oligotrophic oceans. Viruses (cyanophages) can lyse cyanobacterial cells and inhibit their carbon fixation, serving as critical components of the marine carbon cycle. The daily light-dark cycle regulates the growth and carbon fixation of cyanobacteria, and also influences the life cycle of cyanophages. In this project, students will use molecular biology, bioinformatics and biochemistry methods to study the interaction of cyanobacteria and cyanophage under daily light-dark cycles.