Replication of plasmids derived from Shiga toxin-converting bacteriophages in starved Escherichia coli.
نویسندگان
چکیده
The pathogenicity of Shiga toxin-producing Escherichia coli (STEC) depends on the expression of stx genes that are located on lambdoid prophages. Effective toxin production occurs only after prophage induction, and one may presume that replication of the phage genome is important for an increase in the dosage of stx genes, positively influencing their expression. We investigated the replication of plasmids derived from Shiga toxin (Stx)-converting bacteriophages in starved E. coli cells, as starvation conditions may be common in the intestine of infected humans. We found that, unlike plasmids derived from bacteriophage λ, the Shiga toxin phage-derived replicons did not replicate in amino acid-starved relA(+) and relA(-) cells (showing the stringent and relaxed responses to starvation, respectively). The presence of the stable fraction of the replication initiator O protein was detected in all tested replicons. However, while ppGpp, the stringent response effector, inhibited the activities of the λ P(R) promoter and its homologues from Shiga toxin-converting bacteriophages, these promoters, except for λ P(R), were only weakly stimulated by the DksA protein. We suggest that this less efficient (relative to λ) positive regulation of transcription responsible for transcriptional activation of the origin contributes to the inhibition of DNA replication initiation of Shiga toxin-converting bacteriophages in starved host cells, even in the absence of ppGpp (as in starved relA(-) hosts). Possible clinical implications of these results are discussed.
منابع مشابه
ppGpp-dependent negative control of DNA replication of Shiga toxin-converting bacteriophages in Escherichia coli.
The pathogenicity of enterohemorrhagic Escherichia coli (EHEC) strains depends on the production of Shiga toxins that are encoded on lambdoid prophages. Effective production of these toxins requires prophage induction and subsequent phage replication. Previous reports indicated that lytic development of Shiga toxin-converting bacteriophages is inhibited in amino acid-starved bacteria. However, ...
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ورودعنوان ژورنال:
- Microbiology
دوره 157 Pt 1 شماره
صفحات -
تاریخ انتشار 2011