ISOLATION AND CHARACTERIZATION OF A DNA VIRUS INFECTING FELDMANNIA SIMPLEX (PHAEOPHYCEAE)

We report on the isolation and characterization of a virus that is formed in modified zoidangia of the marine brown alga Feldmannia simplex (Crouan) Hamel (Ectocarpales, Phaeophyceae). Isolated virus particles had a buoyant density of about 1.35 g.mL(-1) in CsCl equilibrium gradients. They contained one major polypeptide (MW = 55,000) and at least six additional polypeptides (MW = 15,000-120,000). Four of these proteins were glycosylated, The viral genome consisted of double-stranded DNA and formed two freely migrating fractions in pulsed-field-gel electrophoresis, namely linear DNA with a size of 220 kilobase pairs, and fragments of 10-60 kilobase pairs. However, electron microscopic examination revealed that a substantial fraction of the viral DNA occurred as closed circles. We suggest that the viral DNA in native particles is circular but tends to break at random sites during the preparation.