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Structure of phage ΦX174 capsid Schematic drawing of a Sinsheimervirus (aka Phix174microvirus) virion. The phi X 174 (or ΦX174) bacteriophage is a single-stranded DNA virus that infects Escherichia coli.
The "early", "middle" (DNA replication), and "late" genes (virus structure), roughly represent the time course of gene expression. [74] Bacteriophage genomes can be highly mosaic, i.e. the genome of many phage species appear to be composed of numerous individual modules. These modules may be found in other phage species in different arrangements.
Longer (or shorter) DNA can be included in fd phage, since more (or fewer) protein subunits can be added during assembly as required to protect the DNA, making the phage convenient for genetic studies. [37] [38] The length of the phage is also affected by the positive charge per length on the inside surface of the phage capsid. [39]
The phage first adheres to the cell surface with its tail parallel to or leaning at an angle to the cell surface in the pre-infection stage. The tail then firmly stands on the cell surface and extends its fibers horizontally, rendering the phage infection-competent, after which viral DNA is released into the cell through an extensible tube. [21]
The 'helper' phage infects the bacterial host by first attaching to the host cell's pilus and then, after attachment, transporting the phage genome into the cytoplasm of the host cell. Inside the cell, the phage genome triggers production of single stranded phagemid DNA in the cytoplasm. This phagemid DNA is then packaged into phage particles.
The phage is covered by a protective protein coat. The T2 phage can quickly turn an E. coli cell into a T2-producing factory that releases phages when the cell ruptures. Experiments conducted in 1952 by Alfred Hershey and Martha Chase demonstrated how the DNA of viruses is injected into the bacterial cells, while most of the viral proteins ...
Assembled major coat protein, exploded view. The virion is a flexible filament (worm-like chain) about 6 nm in diameter and 900 nm long.Several thousand copies of a small (50 amino-acid residues) elongated alpha-helical major coat protein subunit (the product of gene 8, or p8) in an overlapping shingle-like array form a hollow cylinder enclosing the circular single-stranded DNA genome.
M13 is one of the Ff phages (fd and f1 are others), a member of the family filamentous bacteriophage ().Ff phages are composed of circular single-stranded DNA (), which in the case of the m13 phage is 6407 nucleotides long and is encapsulated in approximately 2700 copies of the major coat protein p8, and capped with about 5 copies each of four different minor coat proteins (p3 and p6 at one ...