Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Coliphages”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources
PubMedDate not supplied

[Effect of chitosan derivatives on the reproduction of Coliphages T2 and T7].

The effect of chitosan derivatives with different degrees of polymerization and deamination, as well as of chitosan 6-O-sulfate and chitosan N-succinate-6-O-sulfate, on the reproduction of coliphages T2 and T7 in Escherichia coli and on the growth of this bacterium was studied. Chitosan derivatives decreased the yield of coliphages and exhibited bactericidal activity. The efficiency of inhibition of viral infection and the bactericidal activity of chitosan were found to be dependent on the degree of its polymerization. At the same time, there was no correlation between the degree of chitosan deamination and the extent of inhibition of viral infection. Anionic chitosan derivatives virtually did not possess antiviral or bactericidal activity. It is assumed that chitosan blocks some stages of phage reproduction. The decrease in the phage-producing ability of E. coli may also be due to the bactericidal effect of chitosan.

Anti-Bacterial Agents↗
PubMed1964

INFLUENCE OF NONIONIC SURFACTANTS ON BACTERIOPHAGE INFECTIONS. I. EFFECT OF TRITON WR-1339 ON T2 COLIPHAGE INFECTION.

Rose, Michael J., Jr. (Veterans Administration Hospital, Washington, D.C.), Stephen A. Aron, and Bernard W. Janicki. Influence of nonionic surfactants on bacteriophage infections. I. Effect of Triton WR-1339 on T(2) coliphage infection. J. Bacteriol. 87:933-938. 1964.-Plaques formed by T(2) phage on cultures of Escherichia coli strain B from nutrient broth which contained 0.5% Triton WR-1339 were considerably smaller than those formed on cultures from control broth. Pretreatment of phage particles with Triton did not result in small plaques. Results of population studies showed that treated and control cultures had the same growth rates. Similarly, characteristic physiological reactions of treated cultures were the same as those of the controls. Investigation of the phage growth cycle demonstrated that neither the adsorptive phase nor the latent period was affected by cultivation of the host in Triton. However, the burst size of treated cultures was significantly less than that of control cultures. Analysis of the one-step growth curve data showed that Triton did not inhibit bursting of infected cells. It was concluded that the smaller plaque size was a reflection of a reduced yield of mature virulent phage particles from the Triton-treated cultures.

Adsorption↗
PubMed2003

Site-specific recombination in human cells catalyzed by the wild-type integrase protein of coliphage HK022.

The activity of the Integrase (Int) protein encoded by coliphage HK022 was tested in a human cell culture. Plasmids were constructed as substrates that carry the sites of the integration reaction (attP and attB) or the sites of excision (attL and attR). The site-specific recombination reactions were monitored in cis and in trans configurations by the expression of the green fluorescent protein (GFP) as a reporter. Cells cotransfected with the substrate plasmid(s) and with a plasmid that expresses the wild-type Int show efficient integration as well as excision in both configurations. The wild-type Int was active in the human cells without the need to supply the accessory proteins integration host factor (IHF) and excisionase (Xis) that are indispensable for the reaction in the bacterial host.

Catalysis↗
PubMed1997

Metal- and DNA-binding properties and mutational analysis of the transcription activating factor, B, of coliphage 186: a prokaryotic C4 zinc-finger protein.

Coliphage 186 B is a 72-amino acid protein belonging to the Ogr family of analogous transcription factors present in P2-like phage, which contain a Cys-X2-Cys-X22-Cys-X4-Cys presumptive zinc-finger motif. The molecular characterization of these proteins has been hampered by their insolubility, a difficulty overcome in the present study by obtaining B as a soluble cadmium-containing derivative (CdB). Atomic absorption spectroscopy showed the presence of one atom of cadmium per molecule of purified CdB. The UV absorption spectrum revealed a shoulder at 250 nm, characteristic of CysS-Cd(II) ligand-to-metal charge-transfer transitions, and the difference absorption coefficient after acidification (delta epsilon 248, 24 mM-1 cm-1) indicated the presence of a Cd(Cys-S)4 center. Gel mobility shift analysis of CdB with a 186 late promoter demonstrated specific DNA-binding (KD, app 3-4 microM) and the protein was shown to activate transcription in vitro from a promoter-reporter plasmid construct. The B DNA-binding site was mapped by gel shift and DNAase I cleavage protection experiments to an area between-70 and -43 relative to the transcription start site, coincident with the consensus sequence, GTTGT-N8-TNANCCA, from -66 to -47 of the 186 and P2 late promoters. Inactive B point mutants were obtained in the putative DNA-binding loop of the N-terminal zinc-finger motif and in a central region thought to interact with the Escherichia coli RNA polymerase alpha-subunit. A truncated B mutant comprising the first 53 amino acids (B1-53) exhibited close to wild-type activity, showed a DNA-binding affinity similar to that of the full-length protein, and could be reconstituted with either Cd or Zn. Gel permeation analysis revealed that B1-53 was a majority dimeric species whereas wild-type B showed larger oligomers. 186 B therefore exhibits a potentially linear organization of functional regions comprising an N-terminal C4 zinc-finger DNA-binding region, a dispensable C-terminal region involved in protein self-association, and a central region that interacts with RNA polymerase.

Amino Acid Sequence↗
PubMed1996

Defining the SOS operon of coliphage 186.

We have sequenced the LexA-controlled operon of coliphage 186 that carries the tum gene, whose product is necessary for UV induction of the 186 prophage. The operon consists of orf95 and orf97, and we have identified orf95 as the tum gene. The major translation products from orf95 result from internal initiations and modulate Tum activity. Tum is the product of the full-length Orf95 protein. The second gene of the operon, orf97, is of unknown function but, while it has little effect on prophage induction, its presence in the cell totally blocks infection of that cell by 186.

Amino Acid Sequence↗
PubMed1979

Permutation of the DNA in small-headed virions of coliphage P1.

Use of restriction endonucleases Bg/II, EcoRI, BamHI, and HindIII, has established that in small-headed (P1S) virions of coliphage P1, as a population, the entire genome found in big-headed (P1B) virions is represented. In addition, the origin and direction of DNA packaging are identical in P1S and P1B virions.

Coliphages↗
PubMed1976

Growth of coliphage BF23 on rough strains of Salmonella typhimurium: the bfe locus.

Coliphage BF23 develops in Salmonella typhimurium rough strains. The phage is neither restricted nor modified by S. typhimurium. The growth patterns of the phage were slightly different in S. typhimurium than in Escherichia coli, although phage propagated on S. typhimurium is identical to the phage propagated in E. coli by several criteria used. Mutants of S. typhimurium resistant to BF23 were isolated and found to map (by P22- and Pl-mediated transduction) in the same position as bfe mutants of E. coli. The order of genes was: metB - argC - bfe - rif - purD - metA. Phage BF23 does not form plaques on smooth S. typhimurium strains, since the phage fails to adsorb irreversibly to smooth cells. Nevertheless, on solid agar, the phage prevents growth of many (but not all) smooth strains. Moreover, UV- and alkali-inactivated phage BF23, although unable to form plaques on sensitive hosts, retains the ability to prevent growth of the host on solid medium. This ability is sensitive to protease and resistant to DNAse and RNase. Heat treatment of the phage causes rapid loss of the cell-growth-preventing-ability whereas the ability to form plaques is lost much more slowly. These results lead to a proposal that phage BF23 virions carry a colicin-like factor that kills sensitive cells.

Coliphages↗
PubMed1977

Interaction of E. coli RNA polymerase with promotors of coliphage T5: the rates of complex formation and decay and their correlation with in vitro and in vivo transcriptional activity.

The genome of virulent coliphage T5 contains about 30 sites which form stable complexes with E. coli RNA polymerase. Some of these sites bind RNA polymerase with high rates, others form extremely stable complexes as compared with promotors of other E. coli systems. The transcriptional activity of these promotors in vivo and in vitro reflects the rate of complex formation with RNA polymerase rather than the stability of the enzyme/promotor complex. The fastest, i.e. the most active promotors are found in the "early" region of gene expression followed by promotors of the "preearly" class. The few binding sites for the E. coli holoenzyme within the "late" region react more slowly with the enzyme.

Binding Sites↗
PubMed1979

Restriction cleavage maps of coliphages 186 and P2.

The restriction enzymes BamHI, Bg/II, EcoRI, HindIII, PstI, XbaI and XhoI have been used to cleave DNA isolated from the related coliphages P2 and 186 for analysis on 1% agarose gels. Three approaches were used to map the sites of cleavage: a) analysis dependent upon the existence of cohesive termini and availability of viable P2-186 hybrids; b) analysis of double digests and redigests of isolated fragments with a second enzyme and c) analysis of partial digests by transfer to nitrocellulose and hybridization with a single fragment. This last approach and the results obtained from it are detailed in a separate paper (Saint and Egan, 1979). The number of sites of each enzyme are as follows: a) 186, BamHI-7, Bg/II-1, EcoRI-3, HindIII-2, PstI-22, XbaI-0 and Xho-I-1; b) P2, BamHI-3, Bg/II-2, EcoRI-3, HindIII-0, PstI-O, XbaI-1 and XhoI-O. All of these sites have been mapped with the exception of PstI for 186, where only the five sites in the right 35% (the control region) have been mapped.

Coliphages↗
PubMed1978

Electron microscopic analysis of in vitro transcriptional complexes: mapping of promoters of the coliphage T5 genome.

Transcriptional complexes formed in vitro with coliphage T5 DNA as template were analyzed by electron microscopy and the number and location of starting sites utilized by E. coli RNA polymerase were determined. Of the 40 promoters characterized in this way, 6 map in the two terminal "pre-early" regions, 29 in the "early" and 5 in the "late" region. The direction of transcription within the different regions determined in this study agrees with earlier findings derived from RNA synthesized in vivo.

Coliphages↗
PubMed1982

Coliphage 434 tof Protein: NH2-terminal amino acid sequence and kinetic and equilibrium measurements of DNA binding.

Coliphage 434 tof protein was purified to a substantially pure state from lambda imm434 cI dv carrier cells. The minimum molecular weight is 7,500 +/- 500 as estimated by polyacrylamide gel electrophoresis. The amino acid sequence of the nine NH2-terminal residues was determined, by manual Edman degradation of the intact protein, to be Met-Gln-Thr-Leu-Ser-Glu-Arg-Leu-(Lys)-. The purified protein at low concentrations binds specifically to lambda imm434 dv DNA and at high concentrations also binds to lambda imm21 dv and lambda dv DNA. The curve of the specific binding is of Michaelis type, while that of the nonspecific binding is sigmoidal. The specific binding does not show marked temperature dependency at 4 degrees - 37 degrees C. We have analyzed the equilibrium and kinetic data of specific binding. The equilibrium dissociation constant is 1.9 X 10(-11) M at O degree C. The association rate constant and the dissociation rate constant are 1.1-2.9 X 10(8) M-1s-1 and 2.7 X 10(-3)s-1, respectively, at 0 degrees C. The half life of the tof protein-operator DNA complex is 260 s. These results suggest that the tof protein-operator interaction is much weaker than the interaction between the cI repressor and the operator reported by other workers.

Amino Acid Sequence↗
PubMed1983

Factors affecting the enumeration of coliphages in sewage and sewage-polluted waters.

The count of coliphages in naturally polluted waters was found to be dependent on many experimental factors. If Escherichia coli C was used as a host strain, consistently higher counts were obtained than with other strains (B,K-12-derivatives). This could be explained partly by the absence of a restriction system in C. A nutrient medium (modified Scholtens' agar, MSA) was developed with optimal concentrations of calcium- and magnesium-ions. MSA was compared with other media used for phage work and was found to give higher counts than all but one medium, Phage Assay Agar (PAA), which performed equally. If plating was done in a single agar layer in a large-size Petri-dish, higher counts were found than with the well-known double-agar-layer method.

Coliphages↗
PubMed1977

Host factor for coliphage Q beta RNA replication: presence in procaryotes and association with the 30S ribosomal subunit in Escherichia coli.

The Host Factor required for in vitro coliphage Q beta RNA replication, a heat-stable RNA binding protein present in uninfected Escherichia coli, has been detected by both immunological and functional tests in Acinetobacter calcoaceticus, Klebsiella pneumoniae, Pseudomonas aeruginosa and Pseudomonas putida. It was not detectable by these criteria in Bacillus stearothermophilus, Bacillus subtilis, Caulobacter crescentus, Micrococcus lysodeikticus, Rhodopseudomonas capsulata or Saccharomyces cerevisiae. In Escherichia coli the Host Factor protein has been shown to be associated with ribosomes. It is demonstrated here that this association is specific for the 30S ribosomal subunit.

Acinetobacter↗
PubMed1986

Control of gene expression in the P2-related template coliphages. III. DNA sequence of the major control region of phage 186.

The PstI fragment (65.5% to 77.4%) of coliphage 186, known genetically to encode the major control genes, has been sequenced, and an analysis performed to assess coding capacity, transcription-translation signals, and to identify any other significant features. Our analysis indicates that the region encodes: seven genes, including the int and cI genes, which overlap, the late control gene B, and two genes, named CP75 and CP76, encoding potential DNA-binding proteins; a promoter pB and terminator tB for the rightward transcription of the B gene, and we predict the existence of this transcript in a lysogen; a promoter pL and terminator tL for leftward transcription that encodes the int and cI genes, and represents the presumed lysogenic transcript; a promoter pR for rightward transcription to give the presumed (early) lytic transcript that is overlapping and convergent with the lysogenic transcript; and finally, a potential operator site for repressor binding in the region of the pR promoter. Preliminary evidence is presented to support this analysis.

Base Sequence↗
PubMed1988

Control of gene expression in the P2-related temperate coliphages. V. The use of sequence analysis of 186 Vir mutants to indicate presumptive repressor binding sites.

The prophage of coliphage 186 produces a repressor protein that is required for maintenance of lysogeny and that renders lysogenic cells immune to superinfection by 186. The repressor is likely to be a DNA-binding protein that prevents transcription of the 186 early-lytic genes from promoter pR. To identify the binding site of the repressor, we have isolated virulent mutants that are able to form plaques in the presence of repressor and determined their DNA sequences around pR. The mutants all have mutations in an inverted repeat within pR, and we predict that this repeat is the primary binding site of the repressor. Many of the mutants have second mutations near pR, which allow them to form plaques in the presence of higher concentrations of repressor. The sequences containing these "secondary" mutations show no homology with the putative repressor-binding site, and the role of these mutations in virulence is not clear.

Base Sequence↗
PubMed1988

Structure of the ends of the coliphage N4 genome.

The coliphage N4 genome, a linear and double-stranded DNA of approximately 72,000 bases in length, has unique (non-permuted) direct terminal repeats of 390 to 440 base-pairs in length with 3' extensions. The very terminal sequences were determined by the Maxam-Gilbert method after 5' or 3' labeling, while sequences of internal fragments were determined by the dideoxy chain terminator method after cloning them onto M13 phage DNA. The left end of the N4 genome is relatively precise at its 5' terminus, while microheterogeneity of length exists at the 3'-terminal extensions. The predominant species had a 5 or 6 base 3' protruding sequence, 3' CATAA or 3' CATAAA. On the other hand, the right end is variable; there are at least six discrete ends differing from each other by approximately ten base-pairs and giving rise to the variability of the length of the terminal repeats. Each of the six discrete ends has a microheterogeneity of length, especially at the 3' termini. These properties of the terminal redundancy are discussed in conjunction with the mechanism whereby N4 DNA is replicated and processed.

Base Sequence↗
PubMed1989

DNA replication studies with coliphage 186. II. Depression of host replication by a 186 gene.

Using pre-labelling rather than pulse-labelling studies to determine rates of replication, we have shown that coliphage 186 infection is accompanied by a depression in host DNA replication. We have isolated mutants of the phage gene involved and mapped them in the early region of the phage genome. Sequencing the mutants ultimately led us to the identification of the gene that we have named the dhr gene.

Base Sequence↗
PubMed1990

Control of gene expression in the temperate coliphage 186. VIII. Control of lysis and lysogeny by a transcriptional switch involving face-to-face promoters.

The lysogenic and early lytic operons of the temperate coliphage 186 are transcribed divergently. Primer extension mapping of the 5' ends of these in vivo transcripts showed that the rightward lytic promoter, pR, and the leftward lysogenic promoter, pL, are arranged face-to-face, with their transcripts overlapping by 60 bases. We examined the control of transcription from pR and pL using galK as a reporter gene. The product of the lysogenic cI gene strongly repressed pR transcription while allowing pL transcription. The product of the lytic apl gene (formerly CP75) strongly repressed pL transcription while allowing pR transcription. Thus, the cI-pR-pL-apl region functioned as a transcriptional switch, determining whether transcription was lytic or lysogenic. Also, the cI gene product was able to stimulate pL, possibly by alleviating an inhibition of pL transcription caused by convergent transcription from pR. Other consequences of the face-to-face promoter arrangement are discussed.

Base Sequence↗