Lysogenic cycle


Lysogenic cycle

) can release it, causing proliferation of new phages via the lytic cycle. Lysogenic cycles can also occur in eukaryotes, although the method of incorporation of DNA is not fully understood.

Mixed cycles

Following are some types of viruses that replicate by the lysogenic cycle, but also partly by the lytic cycle.

Bacteriophages

Some DNA phages, called temperate phages, only lyse a small fraction of bacterial cells; in the remaining majority of the bacteria, the phage DNA becomes integrated into the bacterial chromosome and replicates along with it. In this lysogenic state, the information contained in the viral nucleic acid is not expressed. The model organism for studying lysogeny is the lambda phage. Roughly 50-60 nucleotides are taken out of the lysogenic pathway and used.

Lysogenic conversion

In some interactions between lysogenic phages and bacteria, lysogenic conversion may occur. It is when a temperate phage induces a change in the phenotype of the bacteria infected that is not part of a usual phage cycle. Changes can often involve the external membrane of the cell by making it impervious to other phages or even by increasing the pathogenic capability of the bacteria for a host.

Examples:
* "Corynebacterium diphtheriae" produces the toxin of diphtheria only when it is infected by the phage β. In this case, the gene that codes for the toxin is carried by the phage, not the bacteria.
* "Vibrio cholerae" is a non-toxic strain that can become toxic, producing cholera toxin, when it is infected with the phage CTXφ.
* "Clostridium botulinum" causes botulism.
* "Streptococcus pyogenes" causes scarlet fever.
* Shiga toxin
* Tetanus

Extra genes present in prophage genomes which do not have a phage function but (may) act as fitness factors for the lysogen are termed "morons". [cite journal |author=Canchaya C, Proux C, Fournous G, Bruttin A, Brüssow H |title=Prophage genomics |journal=Microbiol. Mol. Biol. Rev. |volume=67 |issue=2 |pages=238–76 |year=2003 |url=http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=156470 |pmid=12794192 |doi=10.1128/MMBR.67.2.238-276.2003]

References


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • lysogenic cycle — noun A form of viral reproduction involving the fusion of the nucleic acid of a bacteriophage with that of a host, followed by proliferation of the resulting prophage See Also: lytic cycle …   Wiktionary

  • lytic cycle — noun The normal process of viral reproduction involving penetration of the cell membrane, nucleic acid synthesis and lysis of the host cell See Also: lysogenic cycle …   Wiktionary

  • Bacteriophage — This article is about a biological infectious particle; for other uses, see phage (disambiguation). A bacteriophage (from bacteria and Greek φάγειν phagein to eat ) is any one of a number of viruses that infect bacteria. The term is commonly used …   Wikipedia

  • Transduction (genetics) — Transduction Transduction is the process by which DNA is transferred from one bacterium to another by a virus.[1] It also refers to the process whereby foreign DNA is introduced into another cell via a viral vector. Trans …   Wikipedia

  • lysogeny — The phenomenon by which a bacterium is infected by a temperate bacteriophage whose DNA is integrated into the bacterial genome and replicates along with the bacterial DNA but remains latent or unexpressed; triggering of the lytic cycle may occur… …   Medical dictionary

  • Lysogen — A lysogen or lysogenic phage is a phage that can exist as a prophage within its host organism. A prophage is the phage DNA in its dormant state, and is either integrated into the host bacteria s chromosome or more rarely exists as a stable… …   Wikipedia

  • Virus — This article is about the biological agent. For other uses, see Virus (disambiguation). For a generally accessible and less technical introduction to the topic, see Introduction to viruses. Viruses …   Wikipedia

  • Microbiology — An agar plate streaked with microorganisms …   Wikipedia

  • Pilus — Schematic drawing of bacterial conjugation. 1 Donor cell produces pilus. 2 Pilus attaches to recipient cell, brings the two cells together. 3 The mobile plasmid is nicked and a single strand of DNA is then transferred to the recipient cell. 4… …   Wikipedia

  • Aerobic organism — Aerobic and anaerobic bacteria can be identified by growing them in a liquid culture: 1: Obligate aerobic bacteria gather at the top of the test tube in order to absorb maximal amount of oxygen. 2: Obligate anaerobic bacteria gather at the bottom …   Wikipedia


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.