Chlorella viruses as a source of novel enzymes

A special advantage has been conferred upon Chlorella cells as tools in bio technology when viruses (Phycodnaviridae) infecting Chlorella cells were di scovered and isolated. The viruses are large icosahedral particles (150-200 nm in diameter), containing a giant, 330-380 kbp long, linear dsDNA genome . Recently, the nucleotide sequence of the 330,740-bp genome of PBCV-1, the prototype virus of Phycodnaviridae, was determined, and up to 702 open rea ding frames (ORFs) were identified along the genome. The possible genes pre sent include those encoding a variety of enzymes involved in the modificati on of DNA, RNA, protein and polysaccharides as well as those involved in th e metabolism of sugars, amino acids, lipids, nucleotides and nucleosides. M any of these genes are actually expressed during viral infection, with func tional enzymes detected in the host cytoplasm or incorporated into the viri on. The successful utilization of these viral enzymes as various DNA restri ction and modification enzymes (Cvi enzymes) that are now commercially avai lable is well documented. Also noteworthy are virion-associated chitinase a nd chitosanase activities that have potentially important applications in t he recycling of natural resources. The virions of Chlorella viruses contain more than 50 different structural proteins, ranging in size from 10 to 200 kDa. Some of these proteins may be replaced with useful foreign proteins u sing recombinant DNA technology. The proteins of interest can be recovered easily from the viral particles, and collected by centrifugation after comp lete lysis of the host Chlorella cells.