by Stephen T. Abedon Ph.D. Steve Abedon, Ph.D., has taught well over 100 individual classes and ~10 individual courses (including introductory biology, microbiology, physiology, biochemistry, etc.) over his 30+ years as a college professor. He has over 150 publications, including multiple monographs, and is ranked in the top 1 or 2 percent among researchers of all disciplines worldwide. His research focuses on bacteriophage biology and phage therapy. (abedon.1@osu.edu)
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phage.org/terms/intemperate.html · Abedon’s Books · DOI: 10.5281/zenodo.20173633
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The term intemperate is used equivalently to "virulent" to describe temperate phage mutants that are no longer controlled by a homoimmune prophage's repressor protein. These phages therefore are neither controlled by the repressor associated with other phages nor able to repress their own lytic cycles and thus unable to display lysogenic cycles. Intemperate can be a preferable term to virulent owing to the number of additional meanings associated with both "virulent" and "virulence". See, for example, virulent phage as well as virulent mutant.
From the glossary of Hershey (1971), p. 777, this is a 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."
From the glossary of Hershey (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 less efficiently and permit fewer cells to survive."
Abedon, S.T. (2026). Phage Terms. https://terms.phage.org · 10.5281/zenodo.20173633
Every term in the Glossary of Bacteriophage Terms. The current page is highlighted purple.