phage conversion; a change in the properties of a bacterial cell as a result of its infection with a temperate bacteriophage. For example, a number of strains of the diphtheria bacillus acquire the capacity to form diphtheria toxin immediately after penetration of the phage into the cell and retain that capacity until the moment of the cell’s dissolution (lysis). If lysogenization (the inclusion of a temperate phage in the genome of the bacterium in the form of a prophage) occurs as a result of the infection, the newly acquired properties become hereditary. Loss of the prophage leads to the loss by the bacterium of the properties that originated during the lysogenic conversion. Thus, lysogenic conversion is due to the addition to the bacterial genome of new genetic information, introduced into the bacterial cell by the phage genome.
Changes in the properties of a bacterium through infection with a temperate phage can also result from transduction. However, unlike the changes brought about by transduction, those resulting from lysogenic conversion last only as long as the phage or prophage is present in the cell. Lysogenic conversion may result in inhibition or intensification of enzyme activity or changes in pathogenic properties, colony morphology, or resistance to antibiotics.
A. N. MAISURIAN