Lytic cycle
Say it: LIT-ik SY-kul
The lytic cycle is a viral life cycle in which a phage takes over a bacterial cell, makes many copies of itself, then bursts the cell to release them.
Also: lytic pathway, lytic infection, lytic replication
Definition
What is the lytic cycle?
The lytic cycle is a way a virus reproduces in which it multiplies inside a host cell and then kills the cell by breaking it open, a process called lysis. The term is used mainly for bacteriophages. Virulent phages, such as T4, can follow only the lytic cycle, while temperate phages, such as lambda, can follow either the lytic cycle or the lysogenic cycle.
The cycle is usually taught in five stages. In attachment, the phage binds specific receptors on the bacterial surface. In penetration, it injects its genome while the empty coat stays outside. During biosynthesis, phage genes take over the cell's machinery, often degrading the host chromosome, and direct it to make phage DNA and proteins. In maturation, these parts assemble into new phages. In release, phage proteins break the cell apart: holins punch holes in the inner membrane, endolysins pass through and digest the peptidoglycan wall, and the cell bursts, freeing many new phages at once.
The timing of lysis is controlled by the holin and differs between phages, which affects how many offspring each infected cell releases. In the lab, lytic infection shows up as plaques, clear spots where phages have destroyed patches of a bacterial lawn growing on a dish.
Word parts
Where does the term “lytic cycle” come from?
- lytic
- able to loosen or dissolveGreek lytikos, from lysis, a loosening
- cycle
- circleGreek kyklos
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Terms that go with it
- BacteriophageA bacteriophage, or phage, is a virus that infects bacteria, injecting its genome and using the host cell's machinery to make new phages.
- Lysogenic cycleThe lysogenic cycle is a phage life cycle in which viral DNA joins the host bacterium's chromosome and is copied with it instead of killing the cell.
- VirusA virus is a tiny infectious particle of DNA or RNA inside a protein coat that can multiply only by taking over the machinery of a living host cell.
- CapsidA capsid is the protein shell of a virus that surrounds and protects its genome, built from many repeating protein subunits called capsomeres.
- PeptidoglycanPeptidoglycan is the mesh-like polymer of sugars and short peptides that forms the bacterial cell wall and gives bacteria their shape and strength.
- BacteriumA bacterium is a single-celled prokaryote with no nucleus, found in almost every habitat on Earth, including in and on the human body.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- OpenStax Microbiology, 6.2 The Viral Life Cycle
- Cahill and Young (2018), Phage Lysis: Multiple Genes for Multiple Barriers, Advances in Virus Research
- Clokie et al. (2011), Phages in nature, Bacteriophage
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