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At least 19 recordsLinked to original sources
PubMed1991

Transcriptional analysis of the restriction and modification genes of bacteriophage P1.

Bacteriophage P1 res and mod genes encode the restriction and modification polypeptides of the Type III restriction enzyme EcoP1. Northern blot analysis using res- and mod-specific probes revealed the presence of two separate transcripts in strains harbouring the EcoP1 restriction and modification genes. Furthermore, by constructing a series of fusions with a promoter less lacZ gene, we show that both the res and mod genes are transcribed from separate promoters. A more detailed investigation of the mod promoter region revealed two promoters located some 70 and 140bp upstream from the translational start codon. In addition, another pair of promoters and a further separate promoter are located more than 500bp upstream from this start codon. Two short open reading frames are located between these distal and proximal promoter clusters. Transcription of the res gene is initiated from within the mod open reading frame from two adjacent promoters. In addition a functional promoter is located on the antisense strand close to the res promoter region. The relationship between the transcription units of the res and mod genes is discussed.

Amino Acid Sequence↗
PubMed1972

The deoxyribonucleic acid modification enzyme of bacteriophage P1.

The bacteriophage P1 modification enzyme, assayed by the specific methylation of unmodified bacteriophage 82 DNA, has been purified 500-fold from a bacteriophage P1 lysogen of Escherichia coli. The enzyme catalyses the incorporation of approximately 20-24 methyl groups per bacteriophage 82 DNA molecule. The sole product of methylation is 6-methylaminopurine. Methylation of unmodified bacteriophage DNA confers protection against a challenge by purified bacteriophage P1 restriction enzyme. The pH optimum is 6.0-6.25: the apparent K(m) for S-adenosyl-l-methionine is 5x10(-6)m.

Ammonium Sulfate↗
PubMed1992

DNA inversion regions Min of plasmid p15B and Cin of bacteriophage P1: evolution of bacteriophage tail fiber genes.

Plasmid p15B and the genome of bacteriophage P1 are closely related, but their site-specific DNA inversion systems, Min and Cin, respectively, do not have strict structural homology. Rather, the complex Min system represents a substitution of a Cin-like system into an ancestral p15B genome. The substituting sequences of both the min recombinase gene and the multiple invertible DNA segments of p15B are, respectively, homologous to the pin recombinase gene and to part of the invertible DNA of the Pin system on the defective viral element e14 of Escherichia coli K-12. To map the sites of this substitution, the DNA sequence of a segment adjacent to the invertible segment in the P1 genome was determined. This, together with already available sequence data, indicated that both P1 and p15B had suffered various sequence acquisitions or deletions and sequence amplifications giving rise to mosaics of partially related repeated elements. Data base searches revealed segments of homology in the DNA inversion regions of p15B, e14, and P1 and in tail fiber genes of phages Mu, T4, P2, and lambda. This result suggest that the evolution of phage tail fiber genes involves horizontal gene transfer and that the Min and Pin regions encode tail fiber genes. A functional test proved that the p15B Min region carries a tail fiber operon and suggests that the alternative expression of six different gene variants by Min inversion offers extensive host range variation.

Amino Acid Sequence↗
PubMed1989

Participation of the lytic replicon in bacteriophage P1 plasmid maintenance.

P1 bacteriophage carries at least two replicons: a plasmid replicon and a viral lytic replicon. Since the isolated plasmid replicon can maintain itself stably at the low copy number characteristic of intact P1 prophage, it has been assumed that this replicon is responsible for driving prophage replication. We provide evidence that when replication from the plasmid replicon is prevented, prophage replication continues, albeit at a reduced rate. The residual plasmid replication is due to incomplete repression of the lytic replicon by the c1 immunity repressor. Incomplete repression was particularly evident in lysogens of the thermoinducible P1 c1.100 prophage, whose replication at 32 degrees C remained almost unaffected when use of the plasmid replicon was prevented. Moreover, the average plasmid copy number of P1 in a P1 c1.100 lysogen was elevated with respect to the copy number of P1 c1+. The capacity of the lytic replicon to act as an auxiliary in plasmid maintenance may contribute to the extraordinary stability of P1 plasmid prophage.

Alleles↗
PubMed1983

Replication-control functions block the induction of an SOS response by a damaged P1 bacteriophage.

UV-damaged bacteriophage P1 causes an SOS response in infected bacteria that can be measured colorimetrically with the aid of a lambda pL-lacZ fusion strain of Escherichia coli. This response is blocked by a P1 prophage. Evidence is offered that the blockage is caused by the concerted action of the incompatibility determinant incA and the immunity (c1 and c4) repressors of the prophage. We suggest that indirect induction of lambda by damaged P1 is caused by the abortive initiation of replication in either of two modes, one under incA control, the other under c1 control and indirectly (via ant, the determinant of a repression antagonist) under c4 control.

Bacteriophage lambda↗
PubMed1964

DRUG RESISTANCE OF ENTERIC BACTERIA. IV. ACTIVE TRANSDUCING BACTERIOPHAGE P1 CM PRODUCED BY THE COMBINATION OF R FACTOR WITH BACTERIOPHAGE P1.

Kondo, Eiko (Gunma University, Maebashi, Japan), and Susumu Mitsuhashi. Drug resistance of enteric bacteria. IV. Active transducing phage P1 CM produced by the combination of R factor with phage P1. J. Bacteriol. 88:1266-1276. 1964.-During an investigation of the transduction of R factors with phage P1, a phage lysate capable of transducing the character of chloramphenicol resistance (CM(r)) in extremely high frequency was obtained. The transduction of the CM(r) character with the lysate was consistently accompanied by lysogenization with the phage used for transduction. This lysate exhibits no beneficial effect with normal P1, and no effect is produced by decreasing the multiplicity of infection. A single infection with the phage allows the formation of plaques as well as CM(r) lysogenic cells at the center of the plaque. Both the transducing and plaque-forming activities of the lysate were lost by neutralization with anti-P1 phage serum, and its absorption to the host bacteria was enhanced by the addition of Ca(++). Thus, it was concluded that a derivative of P1 phage (P1 CM) was isolated which had not only the ability to transduce the CM(r) character but also the capacity to form plaques; i.e., the CM(r) gene of R factor is specifically associated with the genome of phage P1. No detectable differences were noted between P1 CM and normal P1 phage in density-gradient analyses in CsCl, in stability of lysogenization, in ability to transduce chromosomal markers, and in the mode of induction from lysogenic cells by ultraviolet irradiation. The instance of transduction of the CM(r) character described here may also be considered as an example of lysogenic conversion, in the sense that the alteration in CM(r) character is inseparable from lysogenicity.

Bacteria↗
PubMed1968

Multiplication of bacteriophage P1 mutants in Shigella dysenteriae strain Sh(P1).

From bacteriophage P1, 10 mutants (P1cl) were isolated which are impaired in their ability to lysogenize Shigella dysenteriae Sh and which fail to make plaques when plated on Sh(P1). When Sh(P1) is infected with P1cl, a considerable proportion of the infected cells is converted into infectious centers, which eventually release P1cl but not P1. This phage release occurs over a period of several hours, during which a manyfold multiplication of infectious centers takes place. In the course of this multiplication, surviving bacteria, lysogenic for P1 only, are produced by segregation. At high multiplicity of infection, Sh(P1) are killed without producing any phage.

Bacteriophages↗
PubMed1981

Genetic studies of H group plasmids by bacteriophage P1 transduction.

Bacteriophage P1 transduction was used to study the incompatibility group H1 plasmid pRG1251, molecular weight 120 x 10(6), and the incompatibility group H2 plasmid pSD114, molecular weight 166 x 10(6). The order of resistance (R) determinants on pSD114 was deduced from transduction and segregation experiments to be chloramphenicol-tetracycline-kanamycin-streptomycin. Resistance to tellurium and to coliphages, which are properties also encoded by many H2 plasmids, were not transduced with the other markers. On pRG1251, the ampicillin and tetracycline resistance markers appear to be located together, as do the chloramphenicol, streptomycin, and sulfamethoxazole resistance markers. Frequently, blocks of R determinants were transposed to the P1 genome or to the Escherichia coli chromosome. P1 DNA was isolated which carried the chloramphenicol, streptomycin, and sulfamethoxazole markers from pRG1251 and had a molecular weight of 64 x 10(6). Other P1 prophages carried R determinants from pSD114 and had molecular weights of 86 x 10(6). A plasmid of molecular weight 124 x 10(6) was also isolated which contained incompatibility determinants from P1 (incompatibility group Y) and from the H2 group plasmid. The mechanism of formation of these unusual plasmid species is discussed.

Anti-Bacterial Agents↗
PubMed1973

The deoxyribonucleic acid-modification enzyme of bacteriophage P1. Subunit structure.

The bacteriophage P1 modification enzyme was purified 1400-fold from induced lysogens of a thermoinducible mutant of bacteriophage P1. The most purified fraction, when analysed by polyacrylamide-gel electrophoresis in sodium dodecyl sulphate, showed two principal stained bands. The two bands co-sedimented in a glycerol gradient with the modification activity, at a rate which, when compared with the rate of sedimentation of marker proteins, corresponds to a sedimentation coefficient in water of 6S. The mobilities of the bands on sodium dodecyl sulphate-polyacrylamide-gel electrophoresis corresponded to polypeptides of molecular weight 70000 and 45000 and they were present in equimolar amounts. It was concluded that the 6S species of the enzyme is a dimer of unlike subunits.

Ammonium Sulfate↗
PubMed1989

Use of a biotinylated DNA probe to detect bacteria transduced by bacteriophage P1 in soil.

Presumptive bacteriophage P1 transductants of Escherichia coli, isolated from soil inoculated with lysates of transducing phage P1 and E. coli, were confirmed to be lysogenic for phage P1 by hybridization with a biotinylated DNA probe prepared from the 1.2-kilobase-pair HindIII 3 fragment of bacteriophage P1. No P1 lysogens of indigenous soil bacteria were detected with the DNA probe. The sensitivity and specificity of the DNA probe were assessed with purified and dot blot DNA, respectively. In addition, two techniques for the lysis and deproteinization of bacteria and bacteriophages on nitrocellulose filters were compared. These studies indicated that biotinylated DNA probes may be an effective alternative to conventional radiolabeled DNA probes for detecting specific gene sequences in bacteria indigenous to or introduced into soil.

Bacteria↗
PubMed1987

A mutational analysis of the bacteriophage P1 recombinase Cre.

Bacteriophage P1 encodes a 38,600 Mr site-specific recombinase, Cre, that is responsible for reciprocal recombination between sites on the P1 DNA called loxP. Using in vitro mutagenesis 67 cre mutants representing a total of 37 unique changes have been characterized. The mutations result in a wide variety of phenotypes as judged by the varying ability of each mutant Cre protein to excise a lacZ gene located between two loxP sites in vivo. Although the mutations are found throughout the entire cre gene, almost half are located near the carboxyl terminus of the protein, suggesting a region critical for recombinase function. DNA binding assays using partially purified mutant proteins indicate that mutations in two widely separated regions of the protein each result in loss of heparin-resistant complexes between Cre and a loxP site. These results suggest that Cre may contain two separate domains, both of which are involved in binding to loxP.

Amino Acid Sequence↗
PubMed1994

Purification and DNA-binding activity of the PacA subunit of the bacteriophage P1 pacase enzyme.

The bacteriophage P1 packaging site (pac) cleavage enzyme (pacase) consists of two phage encoded proteins, PacA and PacB. Both proteins are necessary for the recognition and cleavage of pac and for subsequent packaging of cleaved DNA into phage particles. We have purified PacA to homogeneity from a bacterial strain that overproduces the protein. Purified PacA complements an Escherichia coli extract containing the PacB protein for DNA cleavage at the pac site and recognizes and binds to methylated pac DNA independently of PacB in gel retardation experiments. The latter property of PacA is absolutely dependent on the presence of a wildtype E. coli extract, suggesting that E. coli host proteins play a role in the pac cleavage reaction.

Bacterial Proteins↗
PubMed1999

Identification and characterization of the single-stranded DNA-binding protein of bacteriophage P1.

The genome of bacteriophage P1 harbors a gene coding for a 162-amino-acid protein which shows 66% amino acid sequence identity to the Escherichia coli single-stranded DNA-binding protein (SSB). The expression of the P1 gene is tightly regulated by P1 immunity proteins. It is completely repressed during lysogenic growth and only weakly expressed during lytic growth, as assayed by an ssb-P1/lacZ fusion construct. When cloned on an intermediate-copy-number plasmid, the P1 gene is able to suppress the temperature-sensitive defect of an E. coli ssb mutant, indicating that the two proteins are functionally interchangeable. Many bacteriophages and conjugative plasmids do not rely on the SSB protein provided by their host organism but code for their own SSB proteins. However, the close relationship between SSB-P1 and the SSB protein of the P1 host, E. coli, raises questions about the functional significance of the phage protein.

Amino Acid Sequence↗
PubMed1982

Suppression of the lexC (ssbA) mutation of Escherichia coli by a mutant of bacteriophage P1.

A new mutant of bacteriophage P1 designated lxc that suppresses the phenotype of lexC and ssbA mutants of Escherichia coli was isolated and characterized. The properties of lexC mutants suppressed by the lxc mutation include temperature sensitive growth at 42 degrees C, sensitivity to ultraviolet light and alkylating agents, and a nonmutagenic response following exposure to ultraviolet irradiation. A bac mutant of bacteriophage P1 that suppresses the temperature sensitivity of dnaB mutants does not affect the phenotype of lexC or ssbA mutants. Neither the lxc or bac mutations affect the ultraviolet light sensitivity of strains with the mutations uvrA155, lexA102, or recA56.

Coliphages↗
PubMed1987

Multiple repressor binding sites in the genome of bacteriophage P1.

After digestion of bacteriophage P1 DNA with EcoRI in the presence of P1 repressor, 6 repressor binding sites were identified in 5 of 26 EcoRI fragments. Binding sites were localized by the decreased mobility of DNA fragment-repressor complexes during electrophoresis and by DNase protection ("footprinting") analysis. The repressor binding sites, or operators, comprise a 17-base-pair-long consensus sequence lacking symmetrical elements. Three operators can be related to known genes, whereas the function of the others is still unknown. The mutant P1 bac, rendering ban expression constitutive, is identified as an operator-constitutive mutation of the ban operon.

Bacteriophages↗
PubMed1983

Genome fusion mediated by the site specific DNA inversion system of bacteriophage P1.

The genome of bacteriophage P1 contains a segment which is invertible by site specific recombination between sequences near the outside ends of the inverted repeats which flank it. Immediately adjacent to this C segment is the coding sequence for cin, the enzyme catalyzing inversion. We show that multicopy plasmids carrying cin and the sequences at which it acts (cix) can form dimers in the absence of the host recA function. Further, such plasmids can be cotransduced with P1 markers at high frequency from recA lysogens, indicating cointegration with the P1 genome. It is thus demonstrated that a system whose primary role is the inversion of a specific DNA segment can also mediate intermolecular recombination.

Bacterial Proteins↗
PubMed1977

Effects of mutations in the immunity system of bacteriophage P1.

A mutant of bacteriophage P1 that made an altered c1 repressor is described. The mutant c1 product had two configurations: in lysogens, at high temperatures, it permitted constitutive expression of the normally repressed DNA replication function ban and was insensitive to the action of ant, a product expressed by the virulent mutant P1virs and by the heteroimmune phage P7 (formerly phiamp+) and normally able to overcome c1 repression; in mutant lysogens at low temperatures, the mutant repressor was apparently normal (able to repress ban and sensitive to ant action). Genetic studies of this mutant led to the isolation of a derivative that formed unstable lysogens. These studies suggested that the ban product was normally under c1 control; they further showed that ant overcame c1 repression by inactivating c1 rather than by creating a bypass of repressor activity.

Coliphages↗