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RESEARCH PRODUCT

Icosahedral dsDNA Bacterial Viruses with an Internal Membrane

subject

description

The icosahedral double-stranded DNA bacteriophages containing an internal membrane belong to two families, the Tectiviridae and the Corticoviridae. Members of the Tectiviridae have a linear dsDNA genome (e.g., PRD1) and those of the Corticoviridae have a circular genome (the only example being PM2). The DNA is covered by a membrane which is in turn covered by a protein capsid. The infection cycle begins when spikes on the capsid recognize the host cell receptor and the virus starts the delivery of the genome into the cell cytoplasm. The replication of the virus genome occurs in the cytoplasm. The members of the Tectiviridae may be virulent or temperate; PM2 is virulent. Virulent bacteriophages lyse the cell releasing new viral progeny. Temperate bacteriophages can also do this, or they can enter a resting state called lysogeny, staying dormant within the cell until induced. The members of the Tectiviridae can be divided into two groups: bacteriophages with a broad host range among Gram-negative bacteria and bacteriophages with a specific host range infecting Bacillus species. The Gram-negative bacteria-infecting group have extremely similar genome sequences whereas there is more variation in the Gram-positive bacteria-infecting group. These two groups have very similar structures even though they do not share any sequence similarity.