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Journal of Bacteriology, April 2007, p. 3115-3123, Vol. 189, No. 8
0021-9193/07/$08.00+0     doi:10.1128/JB.01857-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Effect of Salt Shock on Stability of {lambda}imm434 Lysogens{triangledown}

Paul Shkilnyj and Gerald B. Koudelka*

Department of Biological Sciences, University at Buffalo, Buffalo, New York 14260

Received 11 December 2006/ Accepted 4 February 2007

The affinities of the bacteriophage 434 repressor for its various binding sites depend on the type and/or concentration of monovalent cations. The ability of bacteriophage 434 repressor to govern the lysis-lysogeny decision depends on the DNA binding activities of the phage's cI repressor protein. We wished to determine whether changes in the intracellular ionic environment influence the lysis-lysogeny decision of the bacteriophage {lambda}imm434. Our findings show that the ionic composition within bacterial cells varies with the cation concentration in the growth media. When {lambda}imm434 lysogens were grown to mid-log or stationary phase and subsequently incubated in media with increasing monovalent salt concentrations, we observed a salt concentration-dependent increase in the frequency of bacteriophage spontaneous induction. We also found that the frequency of spontaneous induction varied with the type of monovalent cation in the medium. The salt-dependent increase in phage production was unaffected by a recA mutation. These findings indicate that the salt-dependent increase in phage production is not caused by activation of the SOS pathway. Instead, our evidence suggests that salt stress induces this lysogenic bacteriophage by interfering with 434 repressor-DNA interactions. We speculate that the salt-dependent increase in spontaneous induction is due to a direct effect on the repressor's affinity for DNA. Regardless of the precise mechanism, our findings demonstrate that salt stress can regulate the phage lysis-lysogeny switch.

* Corresponding author. Mailing address: Department of Biological Sciences, University at Buffalo, Cooke Hall, North Campus, Buffalo, NY. Phone: (716) 645-2363, ext. 158. Fax: (716) 645-2975. E-mail: koudelka{at}buffalo.edu

{triangledown} Published ahead of print on 16 February 2007.

Journal of Bacteriology, April 2007, p. 3115-3123, Vol. 189, No. 8
0021-9193/07/$08.00+0     doi:10.1128/JB.01857-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

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