Based on the size of its genome, or complete DNA sequence, the microbe dubbed CroV is the second to be considered a "giant virus". The only virus with a larger genome -- Mimivirus -- lives in fresh water.
CroV's enormous, and surprising, genetic code further blurs the boundary between viruses and cellular life, said the researchers who discovered it. According to them, CroV is equipped with genes that allow it to repair its genome, synthesize sugars and even gain more control over the machinery that it hijacks within the host cells to replicate itself, LiveScience reported.
"They take over the cell, and they basically run the cell," said Matthias Fischer, who described CroV for his doctoral dissertation at the University of British Columbia. He added that the production of new CroV viruses within an infected cell resembles an assembly line.
Viruses are essentially genetic material wrapped in a thin protein coat, and they must use the goods of a host in order to make more of themselves. Traditionally, viruses were considered nonliving. But, these discoveries about CroV add more weight to the argument that viruses are alive, Fischer said.
Fischer found that CroV's genome contains approximately 730,000 base pairs, the building blocks of DNA. Mimivirus has a genome of about 1.2 million base pairs. Despite its size, CroV is a threat only to the relatively small. It infects a common, single-celled grazing creature called Cafeteria roenbergensis.
Not surprisingly, the infection kills Cafeteria roenbergensis, according to Curtis Suttle, also a University of British Columbia researcher who worked on the study. This tiny creature may be the most abundant eukaryote, or complex celled organism, in the ocean and perhaps the world, he said. This category includes all animals, plants and many other organisms, Suttle said.
The research is published in the online edition of the Proceedings of the National Academy of Sciences.