ISOLATION AND MOLECULAR CHARACTERIZATION OF 5 MARINE CYANOPHAGES PROPAGATED ON SYNECHOCOCCUS SP STRAIN WH7803

Five marine cyanophages propagated on Synechococcus sp. strain WH7803 were isolated from three different oceanographic provinces during the months of August and September 1992: coastal water from the Sargasso S ea, Bermuda; Woods Hole harbor, Woods Hole, Mass.; and coastal water f rom the English Channel, off Plymouth Sound, United Kingdom. The five cyanophage isolates were found to belong to two families, Myoviridae a nd Styloviridae, on the basis of their morphology observed in the tran smission electron microscope. DNA purified from each of the cyanophage isolates was restricted with a selection of restriction endonucleases , and three distinguishably different patterns were observed. DNA isol ated from Myoviridae isolates from Bermuda and the English Channel had highly related restriction patterns, as did DNA isolated from Stylovi ridae isolates from Bermuda and the English Channel. DNA isolated from the Myoviridae isolate from Woods Hole had a unique restriction patte rn. The genome size for each of the Myoviridae isolates was ca. 80 to 85 kb, and it was ca. 90 to 100 kb for each of the Styloviridae isolat es. Southern blotting analysis revealed that there was a limited degre e of homology among all cyanophage DNAs probed, but clear differences were observed between cyanophage DNA from the Myoviridae and that from the Styloviridae isolates. Polypeptide analysis revealed a clear diff erence between Myoviridae and Styloviridae polypeptide profiles, altho ugh the major, presumably structural, protein in each case was ca. 53 to 54 kDa.