In order to classify bacteriophage ST1, information on its genome and morphology are required. Digestion of the genome of bacteriophage ST1 by the restriction enzyme EcoRI suggests that its genome was double stranded DNA. By using TEM, the bacteriophage was found to have an isometric head with a noncontractile tail. According to the International Committee on Taxonomy of Viruses, tailed bacteriophage with double stranded DNA are classified in the the Caudovirales order. This order contains three families, namely, the Myoviridae (with long, contractile tail), the Siphoviridae (with long, noncontractile tail), and the Podoviridae (with short tail). Based on its genomic and morphological characteristics, the bacteriophage ST1 was tentatively classified as a member of Siphoviridae family.