title: Mechanisms that Determine the Differential Stability of Stx⁺ and Stx(-) Lysogens.
abstract: Phages 933W, BAA2326, 434, and λ are evolutionarily-related temperate lambdoid phages that infect Escherichia coli. Although these are highly-similar phages, BAA2326 and 933W naturally encode Shiga toxin 2 (Stx⁺), but phage 434 and λ do not (Stx(-)). Previous reports suggest that the 933W Stx⁺ prophage forms less stable lysogens in E. coli than does the Stx(-) prophages λ, P22, and 434. The higher spontaneous induction frequency of the Stx⁺ prophage may be correlated with both virulence and dispersion of the Stx2-encoding phage. Here, we examined the hypothesis that lysogen instability is a common feature of Stx⁺ prophages. We found in both the absence and presence of prophage inducers (DNA damaging agents, salts), the Stx⁺ prophages induce at higher frequencies than do Stx(-) prophages. The observed instability of Stx⁺ prophages does not appear to be the result of any differences in phage development properties between Stx⁺ and Stx(-) phages. Our results indicate that differential stability of Stx⁺ and Stx(-) prophages results from both RecA-dependent and RecA-independent effects on the intracellular concentration of the respective cI repressors.
authors.affiliation: Department of Biological Sciences, University at Buffalo, Buffalo, NY 14260, USA. mpcolon@buffalo.edu.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Colon
authors.affiliation: Department of Biological Sciences, University at Buffalo, Buffalo, NY 14260, USA. doloncha@buffalo.edu.
authors.forename: Dolonchapa
authors.initials: D
authors.lastname: Chakraborty
authors.affiliation: Department of Biological Sciences, University at Buffalo, Buffalo, NY 14260, USA. yonatanp@buffalo.edu.
authors.forename: Yonatan
authors.initials: Y
authors.lastname: Pevzner
authors.affiliation: Department of Biological Sciences, University at Buffalo, Buffalo, NY 14260, USA. koudelka@buffalo.edu.
authors.forename: Gerald B
authors.initials: GB
authors.lastname: Koudelka
mesh_terms: D010582:Bacteriophage lambda / Q000235:genetics / Q000502:physiology*; D004926:Escherichia coli / Q000821:virology; D008242:Lysogeny; D039002:Prophages / Q000235:genetics / Q000502:physiology*; D022641:Shiga Toxin 2 / Q000235:genetics*
chemical_list: D022641:Shiga Toxin 2
keywords: RecA; Shiga toxin; bacteriophage; induction; virulence