We are interested in the role of bacteria and their viruses (bacteriophages) in marine ecological processes and the molecular mechanism of their adaptation to the environment. We are using phages that infect the unicellular cyanobacterium Prochlorococcus as a model system. This cyanobacterium is the smallest but the most abundant photosynthetic organism on Earth and it is the dominant primary producer in the oceans. Our ultimate goal is to understand marine ecosystem functioning from the molecular level. We are trying to answer the following questions: How do marine viruses use the host metabolic and signaling networks to adapt to various environmental conditions? How do bacteria and their viruses influence nutrient cycling in the marine ecosystem? How will climate change affect marine microorganisms?