The long term objectives of this project are to elucidate the mechanisms of viral infection and resistance in cyanonbacteria, to apply this knowledge so that the processes of photosynthesis, nitrogen fixation and cellular differentiation can be studied more effectively. Since these processes are fundamental for plant growth thorough understanding of them is crucial to future development of agriculture and improved nutrition. Specifically the cyanobacterium, Anabena variabilis will be infected independently with seven different naturally occurring viruses (cyanophage) and cells resistant to each virus type will be isolated. The virus resistant cell types will then be compared to the sensitive cells to explore the mechanism of virus infection and resistance. These comparisons will be performed by gel electrophoretic analysis of the virus proteins, digestion of cellular and virus DNA with restriction endonucleases and analysis of the DNA fragments by gel electrophoresis and nucleic acid hybridization. DNA fragments identified as involved in cyanophage infection or resistance will be transferred through recombinant DNA methodologies to E. coli host-vector systems for more detailed study.