Abstract
Bacteriophage P1 is among the best described bacterial viruses used in molecular biology. Here, we report that deficiency in the host cell DksA protein, an E. coli global transcription regulator, improves P1 lytic development. Using genetic and microbiological approaches, we investigated several aspects of P1vir biology in an attempt to understand the basis of this phenomenon. We found several minor improvements in phage development in the dksA mutant host, including more efficient adsorption to bacterial cell and phage DNA replication. In addition, gene expression of the main repressor of lysogeny C1, the late promoter activator Lpa, and lysozyme are downregulated in the dksA mutant. We also found nucleotide substitutions located in the phage immunity region immI, which may be responsible for permanent virulence of phage P1vir. We suggest that downregulation of C1 may lead to a less effective repression of lysogeny maintaining genes and that P1vir may be balancing between lysis and lysogeny, although finally it is able to enter the lytic pathway only. The mentioned improvements, such as more efficient replication and more “gentle” cell lysis, while considered minor individually, together may account for the phenomenon of a more efficient P1 phage development in a DksA-deficient host.
Highlights
Bacteriophage P1, along with λ phage and T4, is among the best described bacterial viruses in molecular biology
We discovered that a host cell deficiency in DksA affects bacteriophage P1 life cycle leading to its improved lytic development; we attempt to understand the basis of this effect by using genetic and microbiological approaches
P1vir lytic development is improved in the absence of the DksA protein
Summary
Bacteriophage P1, along with λ phage and T4, is among the best described bacterial viruses in molecular biology. Icd inhibits host cell division which provides time needed for either establishing lysogeny or entering into the lytic pathway [13] Another player in this complex regulation is the Lxc corepressor encoded by the immT region. The late genes, including those whose products are involved in phage morphogenesis, packaging of virus particles and cell lysis, are typically expressed from specific promoter sequences whose transcription requires a phage-encoded regulator, the Lpa protein, defined as an RNA polymerase binding factor [16]. Assembled and accumulated phage particles are released from the host cell due to the action of phage-encoded lysozyme, whose function is controlled by a system of holin and antiholin proteins (LydA and LydB) [17] In their development, bacteriophages rely on and are affected by multiple host regulatory processes and factors. PART II: Functional Transcriptomics of the E. coli DksA-Deficient Cell upon Phage P1vir Infection
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