Lysogenic cycle

Lysogenic cycle as a proliferative form of viruses and phage is referred to, in which the temporarily DNA integrated into the genome of the host and the host cell is not lysed. The Lysogenic cycle describes the Erregerpersistenz for viruses.

Expiration

  • Host cell contacted with a virus ( adsorption)
  • " Injection " of the phage genome, or exposing ( uncoating Sheet or release) of the viral nucleic acid ( DNA or RNA)
  • Integration of the viral genome into the host genome or without integration as an episome or cccDNA present. Retroviruses takes place only transcription of the RNA into DNA, the DNA integration.
  • Rests as prophage or provirus, or cccDNA episome
  • When induced by certain environmental factors enters the virus in the lytic cycle

Lysogenic cycle of phages

In addition to the virulent phage and those occur, thus " moderate" than the rent tempe, are referred to. This name comes from the fact that these phages infect their host cells, but not necessarily lyse. Lysis may, but need not occur. Such a non- lytic infection cycle is called lysogenic.

The lysogenic cycle runs virtually the same analogy to the lytic infection cycle, in terms of adsorption and injection. After the injection, however, there does not to an eclipse, or the metabolism of the host cell is converted to the phage reproduction, the phage DNA binds to the annular genome of the host cell and integrated into the latter.

Lysogenic cycle in phage lambda

The E. coli phage lambda, this integration is effected at a defined location close to the gal operon, and a recombination event. In this case, the host and phage DNA can be cut to form cohesive ends, then re- attached by means of various enzymes. The phage genome is called after this incorporation by André Lwoff prophage. Such a prophage can remain integrated in the genome of the host cell indefinitely and be passed with each cell division of the host to its daughter cells - under certain circumstances it is permanently integrated into the genetic material of the host and thus represents represents a special form of mutation

Transition from the lysogenic to the lytic cycle

A bacterial population containing prophage is used as a lysogen, i.e. generating a lytic principle designated. However, such a culture is quite capable of forming phage, for example after a ( minor, since UV radiation is one of the few means to damage sustained viruses ) UV irradiation or addition of mutagenic substances. Here, there is a so-called induction, which means that the prophage is separated from the bacterial genome, and there is a vegetative propagation and formation of mature phage, followed by lysis as in a lytic infection cycle. Some viruses such as the HIV virus remain several years to decades in the lysogenic cycle, and then moves into a lytic cycle.

Plasmid Lambda phage
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