Lavidaviridae

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Lavidaviridae
Kingdom:	Bamfordvirae
Phylum:	Nucleocytoviricota
Class:	Megaviricetes
Order:	Imitervirales
Family:	Lavidaviridae

Lavidaviridae is a family of viruses that are known to infect giant viruses within the family Mimiviridae. These viruses are unique in that they are considered "virophages," meaning they parasitize other viruses. The name "Lavidaviridae" is derived from "Lavid," which is a reversal of "Dival," a reference to the Mimivirus host, and "viridae," a common suffix for virus families.

Characteristics

Lavidaviridae are small, double-stranded DNA viruses that have a circular genome. They are known for their ability to interfere with the replication of their host giant viruses, thereby reducing the fitness of the host virus. This interaction is a form of parasitism, where the virophage benefits at the expense of the giant virus.

Genome

The genome of Lavidaviridae is relatively small, typically around 19-20 kilobases in length. It encodes for a limited number of proteins, including those necessary for replication and capsid formation. The genome is circular and double-stranded, which is a common feature among many virophages.

Structure

Lavidaviridae virions are icosahedral in shape and have a diameter of approximately 50-70 nanometers. The capsid is composed of proteins encoded by the virophage genome, and it encloses the circular DNA genome.

Life Cycle

Lavidaviridae have a unique life cycle that involves co-infection with a giant virus. When a host cell is co-infected with both a giant virus (such as a Mimivirus) and a Lavidaviridae virophage, the virophage hijacks the replication machinery of the giant virus. This results in the production of new virophage particles while simultaneously inhibiting the replication of the giant virus.

Host Interaction

The interaction between Lavidaviridae and their giant virus hosts is complex. The virophage relies on the giant virus to provide the necessary environment and machinery for replication. However, the presence of the virophage reduces the replication efficiency of the giant virus, which can lead to a decrease in the overall production of giant virus particles.

Ecological and Evolutionary Significance

Lavidaviridae play a significant role in the ecology of aquatic environments, where they are often found. By parasitizing giant viruses, they can influence the population dynamics of these viruses and their hosts, which are often protists. This interaction can have cascading effects on microbial communities and nutrient cycles.

From an evolutionary perspective, Lavidaviridae provide insights into the complexity of virus-virus interactions and the evolution of parasitism. Their existence challenges traditional views of viruses as simple pathogens and highlights the intricate relationships that can exist between different viral entities.

Also see

• Mimiviridae
• Virophage
• Giant virus
• Virus classification