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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.
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.
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.
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]
P1 is a temperate bacteriophage that infects Escherichia coli and some other bacteria. When undergoing a lysogenic cycle the phage genome exists as a plasmid in the bacterium [1] unlike other phages (e.g. the lambda phage) that integrate into the host DNA.
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 ...
Lambda phage is a non-contractile tailed phage, meaning during an infection event it cannot 'force' its DNA through a bacterial cell membrane. It must instead use an existing pathway to invade the host cell, having evolved the tip of its tail to interact with a specific pore to allow entry of its DNA to the hosts.