A new virus infecting the unicellular blue-green alga, Synechococcus strain NRC-1, has been isolated. The virus, named S-1, possesses a head 500 Å in diameter and a narrow, noncontraotile tail 1400 Å in length. The sedimentation coefficient of whole virus particles is 353 S and the buoyant density is 1.501 g/cm3. The major structural proteins have molecular weights of 10,000, 11,000, and 39,000 daltons. S-1 DNA has a contour length of 13.3 ± 0.3 μm and a S20, w of 30.8 ± 1.5 S. These values imply a molecular weight of 23-26 × 106 daltons. The buoyant density in CsCl of S-1 DNA is 1.729 g/cm3, suggesting a GC content of 70%. A slightly higher value, 74%, is derived from the thermal denaturation temperature of S-1 DNA.
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This work was supported by leesearch Grant GB 17514 from the National Science Foundation. K.W.A. was recipient of the James Franck Dissertation Fellowship in Biophysics. We thank Professor IT. Swift for use of his electron microsl:ope and G. Grofman for photographic assist:mcve.
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