Bacteriophage Lytic Cycle

Also called

bacteriophage · phage · T4 phage · virus · lytic cycle · virus life cycle · capsid · tail sheath · tail fibres · lysis · viral replication · host bacterium · E. coli · virus structure · adsorption and penetration · जीवाणुभोजी · विषाणु · लयन चक्र

Topics

• A bacteriophage is a virus that infects bacteria; its protein capsid holds a double-stranded DNA genome.
• Viruses are not cells: they have no cytoplasm or ribosomes and multiply only inside a living host cell.
• The phage lands tail-first; its tail fibres grip receptors on the bacterial cell wall (adsorption).
• The tail sheath contracts and the core pierces the wall; only the DNA enters, the empty capsid stays outside.
• Phage DNA takes over: host DNA is broken down and host ribosomes make phage proteins and DNA copies.
• New capsids, tails and DNA copies assemble into complete phages inside the bacterium.
• An enzyme (lysozyme) bursts the cell wall: lysis releases 100 to 200 new phages to infect other cells.
• In the lysogenic cycle the phage DNA instead joins the host chromosome and is copied with it for generations.

About this model

A GLB file of about 367 KB, shown in Lably's 3D viewer and, on a phone, placed in your room with AR. Credit: Model, science and animation: Lably (built procedurally with three.js; no downloaded meshes). | CC BY 4.0. Original geometry and animation made for Lably.

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