The
Caudovirales are an order of
viruses also known as the
tailed bacteriophages. Under the
Baltimore classification scheme, the
Caudovirales are group I viruses as they have double stranded
DNA (dsDNA) genomes, which can be anywhere from 18,000 base pairs to 500,000 base pairs in length. The virus particles have a distinct shape; each virion has an
icosohedral head that contains the viral genome, and is attached to a flexible tail by a connector protein. The order encompasses a wide range of viruses, many of which containing genes of similar nucleotide sequence and function. Some tailed bacteriophage genomes can vary quite significantly in nucleotide sequence, however, even among the same genus. Due to their characteristic structure and possession of potentially
homologous genes, it is believed these bacteriophages possess a common origin.