Bacteriophage

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A type of virus that infects bacteria. Literally mean, "bacteria eater". Composed of a nucleic acid molecule that is surrounded by a protein structure. It attaches itself to a susceptible bacterium and infects the host cell.

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Bacteriophage

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Lytic Cycle Step 1

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Phage attaches to host cell and injects DNA

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Lytic Cycle Step 2

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Phage DNA circularizes and enters lytic cycle or lysogenic cycle

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Lytic Cycle Step 3

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New phage DNA and proteins are synthesized and assembled into virions.

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Lytic Cycle Step 4

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Cell lyses, releasing phage virions

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Lysogenic Cycle Step 3B

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Phage DNA intergrates within the bacterial chromosome by recombination, becoming a prophage

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Lysogenic Cycle Step 4B

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Lysogenic bacterium reproduces normally

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Lysogenic Cycle Step 5

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Occasionally, the prophage may excise from the bacterial chromosome by another recombination event, initiating a lytic cycle

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Specialized Transduction Step 1

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Prophage exists in galactose-using host (gal-gene)

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Specialized Transduction Step 2

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Phage genome excises, carrying with it the adjacent gal gene from the host

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Specialized Transduction Step 3

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Phage matures and cell lyses, releasing phage carrying gal gene

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Specialized Transduction Step 4

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Phage infects a cell that cannot utilize galactose

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Specialized Transduction Step 5

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Along with the prophage, the bacterial gal gene becomes integrated into the new host's DNA

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Specialized Transduction Step 6

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Lysogenic cell can now metabolize galactose