Temperance
The temperance (from the Latin temperance , moderation ) is a property of certain viruses or bacteriophages . In the case of temperate viruses, in contrast to virulent viruses, the virus genome can be incorporated into the genome of the host under certain circumstances ( lysogenic cycle ). This process is site-specific, i.e. H. a certain temperate phage always inserts its DNA at a defined position within the host genome; as inserts, for example, the phage lambda its genetic material is always between the gal and bio operon in the genome of E. coli a. The stably integrated viral DNA (the so-called prophage ) is then replicated with the bacterial genome and passed on to the resulting cells during division, but at this stage it has no negative impact on the physiology of the cell.
However, certain stimuli such as UV radiation or certain chemicals can induce the excision of the viral DNA in the host cell or in its progeny. This leads to a transition into the lytic cycle . In the course of this, the viral DNA is replicated and the bacterial cell is "reprogrammed" for the synthesis of viral envelope proteins , which finally self- assemble with the replicated DNA to form functional viruses and are released as a result of cell lysis .
If, under certain circumstances, the excision not only of the prophage but also of neighboring DNA sequences of the host genome results in the production of a phage which, in addition to the viral DNA, also contains parts of bacterial genetic information. If such a "recombinant" phage infects a cell, not only viral but also bacterial DNA can be integrated into the host genome during the lysogenic cycle . This form of gene transfer between bacteria by viruses is known as (site) specific transduction .