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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.
A prophage is a bacteriophage (often shortened to "phage") genome that is integrated into the circular bacterial chromosome or exists as an extrachromosomal plasmid within the bacterial cell. [1] Integration of prophages into the bacterial host is the characteristic step of the lysogenic cycle of temperate phages.
During fd phage assembly, the phage DNA is first packaged into a linear intracellular nucleoprotein complex with many copies of the phage gene 5 replication/assembly protein. The gene 5 protein is then displaced by the gene 8 coat protein as the nascent phage is extruded across the bacterial plasma membrane without killing the bacterial host.
In contrast, during electroporation the lipid molecules are not chemically altered but simply shift position, opening up a pore which acts as the conductive pathway through the bilayer as it is filled with water. Electroporation is a dynamic phenomenon that depends on the local transmembrane voltage at each point on the cell membrane.
Electroporation – use of an electrical field to increase cell membrane permeability. Phage therapy – therapeutic use of bacteriophages. Transfection – means of inserting DNA into a cell. Transformation (genetics) – means of inserting DNA into a cell. Viral vector – commonly used tool to deliver genetic material into cells.
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.
3. The phage DNA then moves through the cell to the host's DNA. 4. The phage DNA integrates itself into the host cell's DNA, creating prophage. 5. The prophage then remains dormant until the host cell divides. 6. After the host cell has divided, the phage DNA in the daughter cells activate, and the phage DNA begins to express itself.
The phage particle adsorbs onto the surface of the bacterium using the tail fibers for specificity. The tail sheath contracts and the DNA of the phage is injected into the host cell. The host DNA recombination machinery or the cre enzyme translated from the viral DNA recombine the terminally redundant ends and circularize the genome.