Leviviridae

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Leviviridae
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Family:	Leviviridae

The Leviviridae is a family of RNA viruses that infect bacteria, specifically Escherichia coli and other Enterobacteriaceae. These viruses are characterized by their small, icosahedral capsids and single-stranded, positive-sense RNA genomes. The family is divided into two genera: Levivirus and Allolevivirus.

Structure

Leviviridae virions are non-enveloped and have a diameter of approximately 26 nm. The capsid is composed of 180 copies of a single coat protein arranged in a T=3 icosahedral symmetry. The genome is a linear, single-stranded RNA molecule of about 3,500 to 4,200 nucleotides in length.

Genome and Replication

The genome of Leviviridae viruses encodes four proteins: the maturation protein, the coat protein, the lysis protein, and the replicase protein. The replicase protein is an RNA-dependent RNA polymerase that is essential for the replication of the viral RNA.

Replication occurs in the cytoplasm of the host cell. The virus attaches to the host cell via the maturation protein, which binds to the bacterial pilus. After entry, the viral RNA is translated by the host's ribosomes to produce the viral proteins. The replicase protein then synthesizes a complementary negative-sense RNA strand, which serves as a template for the production of new positive-sense RNA genomes.

Pathogenesis

Leviviridae viruses are lytic, meaning they cause the destruction of the host cell upon release of new virions. The lysis protein is responsible for disrupting the host cell membrane, leading to cell lysis and the release of progeny virions.

Ecology

Leviviridae viruses are found in a variety of environments, including soil, water, and the intestines of animals. They play a role in the regulation of bacterial populations and can be used as model systems for studying RNA virus biology.

Applications

Due to their simplicity and well-characterized genetics, Leviviridae viruses are used as model organisms in molecular biology and virology research. They have been instrumental in understanding the mechanisms of RNA replication and translation.

Also see

• RNA virus
• Bacteriophage
• Icosahedral virus
• Escherichia coli