LARGE-SCALE PRODUCTION AND PLAQUE TITRATION OF EUROPEAN CHLORELLA VIRUSES

Viruses of the exsymbiotic green freshwater algae Chlorella, family Ph ycodnaviridae, appear to be distributed worldwide but those found in N orth American algae have been characterized in detail. The distinct Eu ropean Chlorella viruses were studied and it was necessary to adapt bo th large scale purification and the plaque titration assay to the host organisms' different physiology and to our specific laboratory needs. In the virus purification scheme, a precipitation step with polyethyl ene glycol was introduced which allows high yield recovery of infectiv e particles from large volumes by rapid low-speed centrifugation. In t he plaque assay, a standardized algal culture was introduced. The infl uence of other factors, e.g. circadian rhythm, on plaque growth is als o described. (C) 1997 Elsevier Science B.V.