Affiliation:
1. Department of Biological Sciences, University at Buffalo, Buffalo, New York 14260
Abstract
ABSTRACT
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
c
I repressor protein. We wished to determine whether changes in the intracellular ionic environment influence the lysis-lysogeny decision of the bacteriophage λ
imm434
. Our findings show that the ionic composition within bacterial cells varies with the cation concentration in the growth media. When λ
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.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
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