narrator: matt sullivan, a researcher in chisholm's lab, has been working on isolating these viruses.tified three different viruses affecting the population. using dna sequencing, the team then determines which genes are in these viruses and how they affect the prochlorococcus host cell. surprisingly, they are finding that viruses may not only be helping to kill off these cells, but also to help their hosts adapt to different conditions. sullivan: so, my goal's all in understanding right now the kinds of viruses that are there and how the interaction between the virus and the host cell happens. and wh'snteresti about that is that we can interpret from the genes that are there what processes they're interacting with the host with. so, in one instance, some of these viruses contain core photosynthesis genes. they're actually able to boost photosynthesis during infection in these particular hosts. narrator: a virus infects its host by injecting its genetic material into the cell, causing the cell's biochemistry to switch over to making more virus particles. sometimes dna from the two sou