"Molecular Organization and Intracellular Assembly of Cyanophage Syn5 Infecting Marine Photosynthetic Synechocococcus WH8109".

Jonathan King, Dept. of Biology, MIT, Cambridge, MA 02139

Marine photosynthetic cyanobacteria are responsible for a large fraction of oceanic organic carbon fixation. Cyanophages may play an important role in regulating the marine ecosystem by influencing cyanobacteria communities and mediating lateral gene transfer. Syn5 infecting Synechococcus WH8109 was isolated by J. Waterbury and F. Valois of WHOI.  Conditions for growing the cells and phage to high titer have been developed, allowing characterization of the phage genome, structural proteins, virion organization including the unique horn structure, and intracellular assembly. Advances in electron cryo-tomography (cryoET) yields significant enhancement of image contrast facilitating the direct identification –without fixation and embedding - of carboxysomes, polyribosomes, as well as phage precursors. Phages are assembled through formation of a procapsid empty of DNA, followed by active filling through a portal vertex. This is the pathway found for Adenovirus, Herpesvirus, and all enteric DNA phages, including T4, Lambda, T7, and P22.  The results suggest that the DNA virus morphogenetic pathway evolved from an early common ancestor among marine Cyanophages long before the emergence of terrestrial animals.

Raytcheva, D.A., Haase-Pettingell, C., Piret, J.M. and King, J. (2011) Intracellular assembly of Cyanophage Syn5 proceeds through a scaffold-containing procapsid. J. Virology, 85, 2406-2415.

Pope, W.H., Weigele, P.R., Chang, J., Pedulla, M.L., Ford, M.E., Houtz, J.M., Jiang, W., Chiu, W., Hatfull, G.F., Hendrix, R.W., and King, J. (2007) Genome sequence, structural proteins and capsid organization of the Cyanophage Syn5: A "Horned" bacteriophage of marine Synechococcus. J. Mol. Biol., 368, 966-981.