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PubMed2005

Alteration of tail fiber protein gp38 enables T2 phage to infect Escherichia coli O157:H7.

Artificial control of phage specificity may contribute to practical applications, such as the therapeutic use of phages and the detection of bacteria by their specific phages. To change the specificity of phage infection, gene products (gp) 37 and 38, expressed at the tip of the long tail fiber of T2 phage, were exchanged with those of PP01 phage, an Escherichia coli O157:H7 specific phage. Homologous recombination between the T2 phage genome and a plasmid encoding the region around genes 37-38 of PP01 occurred in transformant E. coli K12 cells. The recombinant T2 phage, named T2ppD1, carried PP01 gp37 and 38 and infected the heterogeneous host cell E. coli O157:H7 and related species. On the other hand, T2ppD1 could not infect E. coli K12, the original host of T2, or its derivatives. The host range of T2ppD1 was the same as that of PP01. Infection of T2ppD1 produced turbid plaques on a lawn of E. coli O157:H7 cells. The binding affinity of T2ppD1 to E. coli O157:H7 was weaker than that of PP01. The adsorption rate constant (ka) of T2ppD1 (0.17 x 10(-9)(ml CFU(-1) min(-1)) was almost 1/6 that of PP01 (1.10 x 10(-9)(ml CFU(-1) min(-1))). In addition to the tip of the long tail fiber, exchange of gene products expressed in the short tail fiber may be necessary for tight binding of recombinant phage.

Bacteriophage T4↗
PubMed1976

Altered properties of deoxyribonucleic acid polymerase I isolated from the membrane of bacteriophage T4-infected Escherichia coli.

Previous studies have shown that a large fraction of the host cell deoxyribonucleic acid (DNA) polymerase I (EC 2.7.7.7) becomes associated with the cell membrane shortly after infection with bacteriophages T4 and T7. The present investigation of the bound enzyme revealed that the polymerase activity can be eluted from the membrane with chelating agents, and that the material thus obtained shows many properties that distinguish it from purified DNA polymerase I. These include its chromatographic behavior, sedimentation rate, sensitivity to anti-DNA polymerase I antiserum, and activity with synthetic and natural DNA primers. Several of these physical and biological parameters were shown to revert slowly during storage to those exhibited by the purified enzyme. Efforts to determine whether the unusual properties of the membrane enzyme resulted from its association with DNA failed to support that possibility. These observations suggest that either the cause or the result of membrane binding of DNA polymerase I is a transient change in conformation or structure of the enzyme, with a resultant change in its enzymatic activity.

Cell Membrane↗
PubMed1969

The relationship of DNA replication to the control of protein synthesis in protoplasts of T4-infected Escherichia coli B.

The relationship of DNA replication to the control of early enzyme synthesis and the formation of late proteins was studied in protoplasts of E. coli B cells infected with an amber mutant, T4am130. In this phage-host system the bacterial DNA is not completely degraded, and the onset and the extent of phage DNA synthesis could be regulated by use of 5-fluorodeoxyuridine and thymidine. It was found that DNA replication is necessary for the transcription of "late" regions of the phage genome and, thus, for the synthesis of late proteins. In addition, the sustained synthesis of late RNA and the tail-fiber protein was shown to require the continued replication of DNA. Furthermore, the mechanism regulating the cessation of early enzyme synthesis appeared to become operative shortly after the onset of DNA replication and required a limited amount of DNA synthesis for its full expression.

Carbon Isotopes↗
PubMed1981

The structure of the capsular polysaccharide (K5 antigen) of urinary-tract-infective Escherichia coli 010:K5:H4. A polymer similar to desulfo-heparin.

The capsular polysaccharide was isolated from Escherichia coli 010:K5:H4; it could not be obtained from a uncapsulated (K5-) mutant. It contains N-acetylglucosamine and glucuronic acid in a molar ratio of 1:1. Acid hydrolysis of the acidic polysaccharide as well as Smith degradation and degradation by deamination of the carboxyl-reduced polysaccharide suggested that the polysaccharide is composed of a disaccharide repeating unit. The data obtained by methylation analysis and nuclear magnetic resonance spectroscopy indicated that the repeating sequence of the capsular polysaccharide is the 4-beta-glucuronyl-1,4-alpha-N-acetylglucosaminyl unit. This structure is similar to that of desulfo-heparin.

Acetylation↗
PubMed1983

Cell-wall lipopolysaccharide of the urinary-tract-infective Escherichia coli 04:K12:H-. Structure of the polysaccharide chain.

The O-specific polysaccharide moiety (04 polysaccharide) of the 04 antigen (lipopolysaccharide) from Escherichia coli 04:K12:H- was isolated in pure form by degradation of the lipopolysaccharide and chromatography on Sephadex G-50. The primary structure of the 04 polysaccharide was elucidated by composition, Smith degradation, nuclear magnetic resonance spectroscopy, methylation and oligosaccharide analysis. Oligosaccharides were obtained by deaminating fragmentation of partially and completely de-N-acetylated polysaccharides. The polysaccharide consists of repeating units of the pentasaccharide (formula; see text) which are joined in the polymer through alpha-1, 4-linkages. The 04 polysaccharide has a mean molecular mass of 13800 Da and consists of the core oligosaccharide and about 14 pentasaccharide repeating units.

Carbohydrate Conformation↗
PubMed1976

[Detection of the products of several T4B phage genes among the proteins of infected Escherichia].

Proteins of wild-type phate T4 and its mutants in genes rII, su(30), stII, stIII, rVI-39 and 60 are studied by means of polyacrylamide gel electrophoresis in the presence of sodium dodecylsulphate of membrane fractions and lysates of infected bacteria. Physiological studies of mutants in these genes carried out by the authors and other investigators allow to suggest that when functions are realized, the products of these genes interact with the plasmatic membrane of the infected bacteria. The product of rIIB cystrone has been indentified as the protein of the membrane of an infected bacterium, its molecular weight being about 30 000. The products of genes su(30), stII, stIII and rVI could not be identified either in lysate or in membrane fraction. The function of gene stII is "superstoichiometric", which may be due to the involvement of a very small product amount when the function of gene stII is realized. Mutants in genes 39 and 60 lack one and the same protein with molecular weight of about 40 000 which is a protein of the membrane of an infected bacterium. This protein may be a product of gene 39, and the functional product of gene 60 is necessary to synthesize it.

Bacterial Proteins↗
PubMed1984

Transcription in bacteriophage f1-infected Escherichia coli: RNA synthesized on DNA of deletion mutant PII shows the existence of a two-site terminator.

Two different transcripts are synthesized on the DNA of deletion mutant PII of bacteriophage f1 in E. coli cells infected with this miniphage. Both RNA species appear to be primary transcripts and differ by about 100 nucleotides at their 3'OH end. Mapping of these molecules on the miniphage genome suggests that a two-site terminator is active at the end of the I region of transcription of bacteriophage f1.

Base Sequence↗
PubMed1968

Reversible repression of early enzyme synthesis in bacteriophage T4-infected Escherichia coli.

A mutant of Escherichia coli B, defective in its accumulation of K(+), was found to synthesize protein at a rate proportional to the level of this cation in the growth medium. When bacteriophage T4-infected cells were incubated in growth medium containing 1 mm K(+), phage deoxyribonucleic acid (DNA) was synthesized at a rate 25% that of normal, and phage protein was synthesized at a rate of 50% of normal. Deoxycytidine pyrophosphatase, a phage-directed early enzyme, shut off at a level of 55% that of normal when infected cells were incubated in medium containing 1 mm K(+). However, deoxycytidine pyrophosphatase synthesis resumed in these cells when they were shifted to medium containing the normal K(+) concentration (33 mm). DNA synthesis also attained the rate characteristic of this K(+) concentration. These results suggest that phage DNA synthesis is not sufficient to repress early protein formation and also indicate that the inhibitor of early protein formation is an early function whose synthesis is sensitive to the same repression as that of the early proteins.

Chloramphenicol↗
PubMed1977

Membrane-associated assembly of M13 phage in extracts of virus-infected Escherichia coli.

Assembly of coliphage M13 is known to occur as the viral DNA crosses the cytoplasmic membrane, shedding its virus-coded DNA unwinding protein and acquiring from the membrane approximately 2400 copies of the major coat protein. Conditions are described in which extracts of M13-infected E. coli and membranes prepared from such extracts will support virus assembly at a rate equivalent to that of intact cells. Extracts prepared from cells infected with temperature-sensitive M13 mutants in genes 1, 3, 4, or 5 are temperature-sensitive in this cell-free assembly reaction. Phage assembly in vitro requires magnesium and as yet an unidentified heat-stable cofactor of low molecular weight. The rate of virus assembly is approximately linear with respect to extract concentration over a 10(4)-fold range, consistent with the observation that the entire M13 assembly activity copurifies with the cell membrane fraction.

Cell Membrane↗
PubMed1976

Phleomycin-induced solubilization of deoxyribonucleic acid in uninfected and T bacteriophage-infected Escherichia coli B.

Phleomycin (PM) induces rapid solubilization of deoxyribonucleic acid (DNA), inhibition of cellular mass increase, and loss of viability when added either to growing cultures of Escherichia coli B or an endonuclease I-defective derivative of B. Nonetheless, bacteriophage of the T-even series are produced, albeit to a reduced extent, when PM is added with phage or after infection to E. coli cells. Bacteriophage T4 infection inhibits the ability of PM to bring about the solubilization of DNA; this effect appears to account for most of the resistance of T-even phage replication to PM. The patterns of inhibition of phage yields obtained when PM is added at infection suggest that glucosylation of T-even phage DNA may also have a protective effect. However, PM induces the solubilization of glucosylated and nonglucosylated DNA at approximately the same rate and thermal denaturation studies indicate that the antibiotic binds both types of DNA equally well. The latter experiments also provided evidence that PM dissociates from DNA at temperatures greater than 80 C.

Anti-Bacterial Agents↗
PubMed1975

Excision of pyrimidine dimers in normal and T4-infected Escherichia coli: effect of polA and other mutations.

Strains carrying both polA1 and recBts1 mutations, which are defective in DNA polymerase I and have thermolabile exonuclease V (the recBC enzyme), are viable at 30 degrees C but not at 42 degrees C. These mutants exhibit almost normal rate of dimer excision in vivo even at the restrictive temperature. Similar results were obtained with other polA minus strains. We have also investigated effect of host and phage mutations on excision of dimers in T4-infected cells. Only a small amount of dimer is excised in T4v-1-infected cells whereas an extensive and selective release of dimers takes place in T4D-infected cells. Other phage mutations, including mutations in gene 43 and gene 30, do not affect excision of dimers in infected cells.

Coliphages↗
PubMed1968

Ribonucleic acid synthesis in T2-infected Escherichia coli during "stringent" control.

The leucine auxotroph Escherichia coli 2961 exhibited stringent control of net ribonucleic acid (RNA) synthesis during amino acid starvation. After leucine was exhausted from the medium, the rate of uracil incorporation into RNA rapidly decreased to 2 to 4% of the prestarvation value. Infection of the starved cells with T2 phage stimulated uracil incorporation to a level equivalent to that of unstarved, T2-infected cells. The RNA synthesized during leucine starvation of the T2-infected cells consisted of T2 and E. coli messenger RNA, but stable ribosomal RNA (23S and 16S) did not appear to be synthesized. It is concluded that one or more T2-specific proteins are required to shut off host messenger RNA synthesis. Furthermore, transcription of E. coli and T2 deoxyribonucleic acid is not necessarily coupled to the translation of messenger RNA during stringent control of net RNA synthesis.

Amino Acids↗
PubMed1998

Abundance in sewage of bacteriophages that infect Escherichia coli O157:H7 and that carry the Shiga toxin 2 gene.

Shiga toxin-converting bacteriophages are involved in the pathogenicity of some enteric bacteria, such as Escherichia coli O157:H7, but data on the occurrence and distribution of such phages as free particles in nature were not available. An experimental approach has been developed to detect the presence of the Shiga toxin 2 (Stx 2)-encoding bacteriophages in sewage. The Stx 2 gene was amplified by PCR from phages concentrated from 10-ml samples of sewage. Moreover, the phages carrying the Stx 2 gene were detected in supernatants from bacteriophage enrichment cultures by using an Stx 2-negative E. coli O157:H7 strain infected with phages purified from volumes of sewage as small as 0.02 ml. Additionally, the A subunit of Stx 2 was detected in the supernatants of the bacteriophage enrichment cultures, which also showed cytotoxic activity for Vero cells. By enrichment of phages concentrated from different volumes of sewage and applying the most-probable-number technique, it was estimated that the number of phages infectious for E. coli O157:H7 and carrying the Stx 2 gene was in the range of 1 to 10 per ml of sewage from two different origins. These values were approximately 1% of all phages infecting E. coli O157:H7.

Animals↗
PubMed2004

Abundance in sewage of bacteriophages infecting Escherichia coli O157:H7.

Bacterial virulence factors such as toxins are often encoded by bacteriophages. Among other examples, factors encoded by phages have been described in some of the emerging or re-emerging pathogens, including the pyrogenic exotoxin A production in group A streptococci, the cholera toxin in Vibrio cholerae, or enterotoxin production in enterohemorrhagic (EHEC) strains of E. coli. Most described virulence factors in Shiga toxin (Stx)-producing E. coli strains are located in mobile genetic elements such as plasmids and bacteriophages. Stx, which are one of the most important virulence elements in Shiga toxin-producing E. coli (STEC), are encoded in the genome of temperate bacteriophages infecting E. coli and other Enterobacteriaceae. Studies on Stx phages indicate that they are transmitted between different bacteria in vivo and in vitro. Phages could also be transmitted extraintestinally, hence the observed presence of infectious Shiga toxin phages in sewage and in fecally contaminated rivers. Stx phages also show a higher persistence under natural inactivation and disinfectant treatments in aquatic environments.This background shows that phages or lysogenic strains carrying Stx2 phages might be the natural reservoir of Stx2 genes and that lysogenization could be the main cause of the emergence of STEC strains, as suggested by several authors. It has also been suggested that lysogenization/conversion processes could take place in food and water and probably inside the human and animal gut. Ingestion of Stx2 phages could produce conversion of non-Stx2-E. coli strains, present inside the gut and producing new pathogenic strains. To control these phenomena, it is first necessary to gain more information about the distribution of Stx phages in the environment. For this purpose, a method of detecting Stx2 phages present in environmental water samples has been developed. The particularity of this method is that it allows detection of all (infectious and noninfectious) Stx2 phages in a water sample; in a second stage, the method allows detection of those phages able to infect and replicate on E. coli O157:H7. Although this method has been applied to Stx2 phages able to infect E. coli O157:H7, it is also applicable to detection in the natural environment of other genes carried by other bacteriophages and other bacteria.

Bacteriophages↗
PubMed1978

Folate polyglutamates in T4D bacteriophage and T4D-infected Escherichia coli.

The folate compound which is a structural component of the Escherichia coli T-even bacteriophage baseplates, has been identified as the hexaglutamyl form of folic acid using a new chromatographic procedure (Baugh, C.M., Braverman, E. and Nair, M.G. (1974) Biochemistry 13, 4952-4957). It has also been found that the host cell contains a variety of polyglutamyl forms of folic acid. The major form is the triglutamate (about 50%) but small amounts of higher molecular weight folates including the octaglutamate (1.8%) have been identified. Upon infection with wild-type T4D bacteriophage there is a shift in the distribution of the folate compounds so that the folyl polyglutamyl compounds having the higher molecular weights are increased. Infection of E. coli with baseplate mutants of T4D containing an amber mutation in gene 28 resulted in the formation of significant amounts (over 7%) of folate compound(s) of molecular weight much higher than those observed either in uninfected cells or cells infected with wild-type T4D. It is suggested that the T4D gene 28 product functions to cleave glutamate residues from high molecular weight folyl polyglutamates to increase the availability of the folyl hexaglutamate for virus assembly.

Coliphages↗
PubMed2000

Occurrence of phages infecting Escherichia coli O157:H7 carrying the Stx 2 gene in sewage from different countries.

Shiga toxin-converting bacteriophages are involved in the pathogenicity of some enteric bacteria, such as Escherichia coli O157:H7. Recent studies have demonstrated a relatively high presence of Shiga toxin 2 phages in sewage from Spain, but no data on sewage from other areas were available. In order to evaluate the presence of such phages in sewage from diverse geographical origins, 33 sewage samples, including samples from eight different European countries as well as from New Zealand and South Africa were analysed. Using an experimental approach based on the detection of Stx 2 gene by a phage enrichment culture followed by PCR, bacteriophages infecting E. coli O157:H7 carrying the Shiga toxin 2 gene were detected in 15 of the samples studied. Results presented here show that the presence of phages carrying the Stx 2 gene is common in sewage from developed countries.

Bacterial Toxins↗
PubMed1998

Stochastic kinetic analysis of developmental pathway bifurcation in phage lambda-infected Escherichia coli cells.

Fluctuations in rates of gene expression can produce highly erratic time patterns of protein production in individual cells and wide diversity in instantaneous protein concentrations across cell populations. When two independently produced regulatory proteins acting at low cellular concentrations competitively control a switch point in a pathway, stochastic variations in their concentrations can produce probabilistic pathway selection, so that an initially homogeneous cell population partitions into distinct phenotypic subpopulations. Many pathogenic organisms, for example, use this mechanism to randomly switch surface features to evade host responses. This coupling between molecular-level fluctuations and macroscopic phenotype selection is analyzed using the phage lambda lysis-lysogeny decision circuit as a model system. The fraction of infected cells selecting the lysogenic pathway at different phage:cell ratios, predicted using a molecular-level stochastic kinetic model of the genetic regulatory circuit, is consistent with experimental observations. The kinetic model of the decision circuit uses the stochastic formulation of chemical kinetics, stochastic mechanisms of gene expression, and a statistical-thermodynamic model of promoter regulation. Conventional deterministic kinetics cannot be used to predict statistics of regulatory systems that produce probabilistic outcomes. Rather, a stochastic kinetic analysis must be used to predict statistics of regulatory outcomes for such stochastically regulated systems.

Bacteriophage lambda↗