Myoviridae

Myoviridae is a family of tailed bacteriophages characterized by a distinctive contractile tail. Virions possess icosahedral capsids containing double-stranded DNA and a long, contractile tail that ends in a baseplate with tail fibers. The tail sheath can contract to drive the tail tube through the bacterial cell envelope during infection.

Genomes are linear double-stranded DNA, typically large, ranging from about 30 to over 200 kilobases, encoding hundreds of proteins involved in replication, transcription, particle assembly, and lysis.

Lifecycle is predominantly lytic, though temperate members may exist in some lineages. Infection begins with adsorption to a receptor on Gram-negative bacteria, DNA injection, replication, assembly, and lysis mediated by holins and endolysins.

Ecology and hosts: Many Myoviridae infect Gram-negative bacteria including Escherichia, Salmonella, Vibrio, and Pseudomonas; they are found in soil, freshwater, and marine environments. The Escherichia coli phage T4 is a well-known example and serves as a model system for studying phage biology.

Taxonomy and significance: Myoviridae is a family within the broader group of tailed bacteriophages historically classified under Caudovirales, recognized for their contractile tails. The family comprises numerous genera and species, reflecting diverse host ranges and genome architectures.

Applications and research: Members of Myoviridae have played a central role in molecular biology and genetics and are subjects of ongoing research in phage therapy, bacterial resistance, and phage-host interactions. They remain key models for understanding tail-mediated infection and viral assembly.