English: Chlorella cells and chlorovirus: Paramecium bursaria chlorella virus-1 (PBCV-1). (A) Plaques formed by PBCV-1 on a lawn of C. variabilis NC64A. (B) The ciliate Paramecium bursaria and its symbiotic chlorella cells. (C) The heliozoon Acanthocystis turfacea and its symbiotic chlorella cells. (D) Cross section of a five-fold averaged cryo-EM image of PBCV-1 reveals a long narrow cylindrical spike structure at one vertex and the viral internal membrane (green) surrounding the viral genome asymmetrically. (E) Cross-section of a five-fold averaged cryo-EM of PBCV-1 as the virus is getting ready to release its DNA into the host cell. (F) Attachment of PBCV-1 to the algal cell wall and degradation of the wall at the point of attachment. This occurs within 1–3 min post infection (p.i.). (G) PBCV-1 particles assemble in defined areas in the cytoplasm named virus assembly centers at ~5 h p.i. Note both DNA containing (dark centers) and empty capsids. (H) A model showing that the origin of the PBCV-1 internal membrane arises from nuclei-derived cisternae, which serve as precursors for the single bi-layered virus membrane. Note, the membrane serves as the template for the capsid structures to form virus particles. (I) Localized lysis of the cell plasma membrane and cell wall and release of progeny viruses at ~7 h p.i. Panels D and E are from the cover of J. Virology issue 17, 2012.