Affiliation:
1. Institute of Biology, University of Szczecin, 71-412 Szczecin, Poland
2. Institute of Biological Science, Faculty of Biological Sciences, University of Zielona Góra, 65-516 Zielona Góra, Poland
3. Institute of Veterinary Medicine, Faculty of Biological and Veterinary Sciences, Nicolaus Copernicus University in Toruń, 87-100 Toruń, Poland
Abstract
In this paper, the characteristics of 40 so far described virophages—parasites of giant viruses—are given, and the similarities and differences between virophages and satellite viruses, which also, like virophages, require helper viruses for replication, are described. The replication of virophages taking place at a specific site—the viral particle factory of giant viruses—and its consequences are presented, and the defence mechanisms of virophages for giant virus hosts, as a protective action for giant virus hosts—protozoa and algae—are approximated. The defence systems of giant viruses against virophages were also presented, which are similar to the CRISPR/Cas defence system found in bacteria and in Archea. These facts, and related to the very specific biological features of virophages (specific site of replication, specific mechanisms of their defensive effects for giant virus hosts, defence systems in giant viruses against virophages), indicate that virophages, and their host giant viruses, are biological objects, forming a ‘novelty’ in biology.