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» Economics » Microbiology » Topics begins with L » Lyti cycle

Page modified: Wednesday, July 13, 2011 15:03:31

During the virus virusvermehrung one differentiates a lytischen and a lysogenen cycle.

The lytische cyclecycle cycle of a virus is connected with the death of the landlord cell; it lysiert. The again produced viruses to dismiss and know again new cells strike, this concerns virulente viruses. The lysierte bacterium dismisses between 100 and 200 phages (throw size).

The lytische cycle of E. coli with that phages T4 lasts with 37"°C 20 to 30min.

  • Landlord cell - contact with virus (Adsorbtion)
  • "Injection" of the virus gene COM (DNA or RNA)
  • Integration of the virus gene COM into the Wirtsgenom (with RNA viruses only Transskription in DNA then integration)
  • Vermehrung of the Viruspartikel
  • Lyse of the landlord cell
  • Infection of further cells

In the following the procedure for even-numbered phages of the T-row is described, other phages can show deviating operational sequence in some details. The lytische infection cycle runs accurately after under 3.) described pattern: Meet a phage on a be suitable cell and come with it in contact, adsorb he with fiber and spike specific component the cell. With these receptors it concerns among other things antigen structures, Lipoproteine or Lipopolysaccharide on the landlord cell surface, for which the appropriate phage an affinity possesses. This affinity avowedly also strict landlord specificity, to which phages - only the phage, whose proteins from end plate, tail fibers and spikes to the receptor on the landlord cell surface fits, are subject can andocken to the cell "". Is missing if the receptor natural-proves (it around the wrong bacterium acts there) or it through mutation was lost, the cell is insensitively, thus resistant for an infection by the phages concerned. From this resistant clones can develop. Is adsorbed the phage to the cell wall (the process is irreversible and can be regarded thus as an antigen anti-body reaction), a contraction of the tail sheath with simultaneous penetration of the tail pipe runs off by the cell wall. This procedure prepares the injection of the phage DNA and by simultaneous delivery by lytischen phage enzymes, which weaken the cell wall, is supported. With injection of the phage gene COM the empty protein covering from Capsid and injection apparatus on the surface of the landlord cell stays. This one calls Viruspartikel staying without DNA ghost. Immediately after the injection of the phage DNA no phages and/or no phage particles can be proven, this period Eklipse or latency are called in the bacteria cell. With Escherichia coli this latency amounts to about 10 minutes. During this time only apparently nothing happens in the cell. During this phase the entire metabolism of the landlord cell is actually changed over to production by phage construction units. Thus the cell division and the synthesis of bacterial DNA presently/immediately after the injection of the viralen DNA are stopped, as by cellown enzymes the virale DNA is transliterated into one mRNA and proteins is synthesized, which interrupt the bacteriaown DNA synthesis, which divide already existing bacterial DNA into fragments and synthesize from this new phage DNA. In the further process of the infection also so-called "‚late `genes are transliterated, which the synthesis of structure proteins (like head, tail pipe, tail fibers etc.) to cause. These construction units are built up in the landlord cell to new phages. The occurrence first assembled phages terminates the Eklipse. From now on phages are assembled, until the internal pressure of the landlord cell exceeds a certain measure and breaks already the cell wall weakened by a Lysozym similar enzyme, which is synthesized parallel to the synthesis of the phage particles. Thus the again formed phages are set free. One calls this procedure Lysis. One calls phages, which release a Lysis with a landlord cell, virulent.

Articles in category "Lyti cycle"

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» Lactase
» Landlord (medicine)
» LB-medium
» Leeuwenhoek medal
» Limnomikrobiologie
» Lysogener cycle
» Lyti cycle

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