bacteriophage phi X 174

Bacteriophage phi X 174 is a small, tailless icosahedral virus belonging to the family Microviridae and genus Microvirus. It infects Escherichia coli (E. coli) bacteria and contains a circular single-stranded DNA (ssDNA) genome of approximately 5,386 nucleotides—the first DNA genome ever sequenced. The virion consists of a protein capsid composed mainly of F and G proteins with additional H and J proteins; the core contains the viral ssDNA. Upon infection, the phage attaches to E. coli via its G protein binding to lipopolysaccharides on the bacterial surface and injects its genome into the host cell using H protein as a pilot for DNA entry. Replication proceeds through synthesis of a complementary negative strand forming double-stranded intermediates that serve as templates for mRNA transcription and further ssDNA synthesis by rolling circle replication. Phi X 174 encodes overlapping genes due to its compact genome; key proteins include A (replication), B (capsid morphogenesis), C (phage maturation), D (assembly), E (host cell lysis via inhibition of peptidoglycan synthesis by targeting MraY enzyme in complex with SlyD from host), F/G/H/J/K structural or assembly roles. Clinically, bacteriophage phi X 174 is used as an investigational T cell-dependent neoantigen for assessing antibody responses in patients with suspected primary immunodeficiencies such as common variable immunodeficiency or hypogammaglobulinemia[6]. It also serves as a model organism in molecular biology research and quality control applications such as water testing[4][8].

Other names

Escherichia coli bacteriophage Phi X174Microvirus φX174