Bacteriophage Ecology Group

Bacteriophage Ecology Group Bacteriophage Ecology Group

Intemperate

Direct descendant of a temperate phage that is able to successfully infect otherwise homoimmune lysogens but unable to display lysogeny.

The term intepemperate is used equivalently to "virulent" to describe temperate phage mutants that are no longer controlled by a homoimmune prophage's repressor protein and therefore both not controlled by the repressor associated with other phages nor able to repress their own lytic cycles and thus unable to display lysogenic cycles. It is a preferable term to virulent owing to the number additional meanings associated with both "virulent" and "virulence". See, for example, virulent phage.

From the glossary of The Bacteriophage Lambda (1971) (p. 777), this is definition of "virulent": "A virulent or intemperate phage species is one unable to lysogenize its host. Virulent mutants of λ are able to grow in immune cells as a result of mutational loss of ability to bind repressor."

Also from the glossary of The Bacteriophage Lambda (1971) (p. 773) note also this definition of "clear" (as in, "clear" plaque): "Lambda and other temperate phages form plaques that are turbid owing to growth of cells surviving the infection. Mutants forming clear plaques (clear mutants) establish immunity loss efficiently and permit fewer cells to survive."

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