Leviviridae

Leviviridae is a family of positive-sense single-stranded RNA viruses. These viruses are known to infect prokaryotes, specifically bacteria. The family currently contains only one genus, Levivirus, and one species, Muscoviridae bacteriophage MS2. The virions are small and non-enveloped, with an icosahedral capsid. The genome is approximately 3,500 nucleotides in length and encodes a limited number of proteins, typically including an RNA-binding protein (maturation protein), a lysis protein, a coat protein, and an RNA replicase.

Leviviridae viruses replicate in the cytoplasm of their bacterial hosts. The viral RNA genome serves directly as messenger RNA, allowing for immediate translation of viral proteins upon entry into the host cell. Replication involves the synthesis of a negative-sense RNA intermediate, which then serves as a template for the production of new positive-sense RNA genomes. The assembly of new virions occurs within the cytoplasm, and progeny are released through lysis of the host cell, mediated by the viral lysis protein.

These phages are well-studied due to their relatively simple structure and rapid replication cycle. Bacteriophage MS2, the representative member of this family, has been a valuable model organism for research in virology, molecular biology, and genetics. Its genetic material has been extensively characterized, and its replication mechanism has provided fundamental insights into RNA virus replication. Leviviridae have also been explored for potential applications in phage therapy, targeting specific bacterial pathogens.