Temperateness (virology)

Temperance ( from the Latin temperance, moderation ) is a property of certain viruses or bacteriophages. In temperate viruses in contrast to virulent viruses, the virus genome can be installed under certain circumstances, into the genome of the host ( lysogenic cycle). This process is site-specific, that is, a certain tempe renter phage DNA inserted its always at a defined site within the host genome; so, for example, the phage lambda inserts its genetic material always between the gal and bio operon in the genome of E. coli. Stably integrated viral DNA ( the so-called prophage ) is then replicated with the bacterial genome and propagated in the division of the resulting cells, however, in this stage, no negative effect on the physiology of the cell.

Certain stimuli such as UV radiation or certain chemicals, however, can induce the excision of the viral DNA into the host cell or in their offspring. This leads to a transition in the lytic cycle. In the course of the viral DNA is replicated and the bacterial cell is " reprogrammed " in the synthesis of viral coat proteins, eventually with the replicated DNA into functional virus -assemble ( self-assembly ), and are released as a result of cell lysis.

If, under certain circumstances, for excision of the prophage is not only but also of adjacent DNA sequences of the host genome, this leads to the production of a phage, which also carries, in addition to the viral DNA components of bacterial genetic information in itself. Infected such a " recombinant " phage a cell, it can come into the host genome as part of the lysogenic cycle to integrate not only viral but also bacterial DNA. This form of gene transfer between bacteria by viruses is called a ( local ) specific transduction.

• Virology