Abstract
BackgroundThe lysis-lysogeny decision in the temperate coliphage λ is influenced by a number of phage proteins (CII and CIII) as well as host factors, viz. Escherichia coli HflB, HflKC and HflD. Prominent among these are the transcription factor CII and HflB, an ATP-dependent protease that degrades CII. Stabilization of CII promotes lysogeny, while its destabilization induces the lytic mode of development. All other factors that influence the lytic/lysogenic decision are known to act by their effects on the stability of CII. Deletion of hflKC has no effect on the stability of CII. However, when λ infects ΔhflKC cells, turbid plaques are produced, indicating stabilization of CII under these conditions.ResultsWe find that CII is stabilized in ΔhflKC cells even without infection by λ, if CIII is present. Nevertheless, we also obtained turbid plaques when a ΔhflKC host was infected by a cIII-defective phage (λcIII67). This observation raises a fundamental question: does lysogeny necessarily correlate with the stabilization of CII? Our experiments indicate that CII is indeed stabilized under these conditions, implying that stabilization of CII is possible in ΔhflKC cells even in the absence of CIII, leading to lysogeny.ConclusionWe propose that a yet unidentified CII-stabilizing factor in λ may influence the lysis-lysogeny decision in ΔhflKC cells.
Highlights
The lysis-lysogeny decision in the temperate coliphage l is influenced by a number of phage proteins (CII and CIII) as well as host factors, viz. Escherichia coli HflB, HflKC and HflD
Role of HflKC on the proteolysis of CII in vivo E. coli HflKC inhibits the proteolysis of all the membranous substrates of HflB (e.g., SecY, YccA) [18]
We measured the stability of CII expressed from the plasmid pKP219 in wild type and in AK990 (ΔhflKC) cells
Summary
We find that CII is stabilized in ΔhflKC cells even without infection by l, if CIII is present. We obtained turbid plaques when a ΔhflKC host was infected by a cIII-defective phage (lcIII67). This observation raises a fundamental question: does lysogeny necessarily correlate with the stabilization of CII? Our experiments indicate that CII is stabilized under these conditions, implying that stabilization of CII is possible in ΔhflKC cells even in the absence of CIII, leading to lysogeny This observation raises a fundamental question: does lysogeny necessarily correlate with the stabilization of CII? Our experiments indicate that CII is stabilized under these conditions, implying that stabilization of CII is possible in ΔhflKC cells even in the absence of CIII, leading to lysogeny
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