Award: OCE-1332740

There are millions of viruses in a liter of seawater. Luckily these viruses don?t affect humans, but primarily bacteria that specialize on living in the ocean. Even though they are tremendously abundant, we still have little idea about the role these viruses. Estimates about viral-caused mortality, and therefore the impact of viruses on marine nutrient cycling, vary widely. One thing is clear, however. Marine viruses are extremely diverse and vary greatly in which bacterial hosts they infect and kill. In this project, we aimed to understand more about "who infects whom" – which viruses infect which bacteria. We used a network-based framework to investigate marine virus-host interactions in the ocean. The research focused on cyanophages, viruses that infect Synechococcus, an ecologically important bacterium in the oceans. To investigate "who infects whom," we used laboratory coevolution experiments and genome sequencing to identify genetic signature of cyanophage-Synechococcus interactions. We identified particular regions of the viral genome that appear to be responsible for determining whether a cyanophage can infect its host. We also compared these results to hundreds of genome sequences from a natural cyanophage population off the coast of southern California. This analysis showed that this population is coevolving with its bacterial host over a five year collection period. Finally, we improved a protocol called viral-tagging which can be used to investigate which viruses infect which hosts, without having to isolate the host bacteria. We demonstrated that the method can be used to estimate the proportion of Synechococcus cells that each virus can infect. At UCI, this project supported the training of 9 undergraduate students, 3 PhD students, and a postdoc. We also established an outreach program at Crystal Cove State Park in Newport Beach, CA. The Park is host to more than 1.2 million visitors and 10,000 K-12 students a year. The program has been expanded to include several other PIs at UCI. UCI undergraduates now begin the program in the fall, completing training about translating science to the public throughout the academic year before working on translating our lab?s research, and the importance of microorganisms in ecosystem functioning, to a variety of educational programs at the park. Last Modified: 08/24/2017 Submitted by: Jennifer B Martiny The project resulted in a new dataset containing cyanophage sequences submitted to BCO-DMO (658729), which builds on a previous dataset (3507) that report the environmental data from the same water samples. The project also resulted in curricular materials for 7th graders as part of a citizen science project in Crystal Cove State Park. Background material for this lesson about the role microorganisms play in decomposition is under review as a distinct publication. Last Modified: 10/25/2017 Submitted by: Jennifer B Martiny