Isolation and partial chemical characterization of a virus-like particle from a eukaryotic alga

A virus-like particle (VLP) associated with the green alga Cylindrocapsa geminella has been purified and partially characterized. The Cylindrocapsa VLP (C-VLP) has a polygonal profile in sectional view, ranges in diameter from 200 to 230 nm, and has a complex, multilayered capsid. Purified VLPs, when analyzed by SDS-polyacrylamide gel electrophoresis, contained at least 10 proteins ranging in molecular weight from 10,000 to 160,000. The C-VLP contains DNA, most probably double-stranded, having an estimated molecular weight of 175-190 x 10(6). Intracellular VLPs were only observed within single-celled germlings and all cultures examined produced the VLP. Generally, only 4-6% of the single-celled germlings contained VLPs, which resulted in cell death. The physicochemical and biological characteristics of the C-VLP support the conclusion that the C-VLP is, in fact, a virus.