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At least 73 records · Page 4Linked to original sources
PubMed1964

LYSIS-FROM-WITHOUT OF STAPHYLOCOCCUS AUREUS STRAINS BY COMBINATIONS OF SPECIFIC PHAGES AND PHAGE-INDUCED LYTIC ENZYMES.

Ralston, Doris J. (University of California, Berkeley) and Mary McIvor. Lysis-from-without of Staphylococcus aureus strains by combinations of specific phages and phage-induced lytic enzymes. J. Bacteriol. 88:676-681. 1964-Several typing phages, adsorbed in sufficient concentrations to their homologous propagating strains, altered the cell surface so as to render the cells sensitive to rapid and synergistic lysis by extra-cellular additions of wall lysins. Lysis was effected both by lysins induced by the individual phages and by phage K(1) virolysin. Phage K(1) also rendered cells sensitive to the lysins of the typing phages. With the exception of lysins from PS 53, 70, and 77, none of the lysins nor purified phages tested separately caused significant lysis of living cells. Lysis-from-without in Staphylococcus aureus appears to be a stepwise process: sensitization by phage followed by digestion of the wall by lysin.

Bacteriolysis↗
PubMed2005

Synonymous codon usage bias in 16 Staphylococcus aureus phages: implication in phage therapy.

To reveal the factors influencing architecture of protein-coding genes in staphylococcal phages, relative synonymous codon usage variation has been investigated in 920 protein-coding genes of 16 staphylococcal phages. As expected for AT rich genomes, there are predominantly A and T ending codons in all 16 phages. Both Nc plot and correspondence analysis on relative synonymous codon usage indicates that mutation bias influences codon usage variation in the 16 phages. Correspondence analysis also suggests that translational selection and gene length also influence the codon usage variation in the phages to some extent and codon usage in staphylococcal phages is phage-specific but not S. aureus-specific. Further analysis indicates that among 16 staphylococcal phages, 44AHJD, P68 and K may be extremely virulent in nature as most of their genes have high translation efficiency. If this is true, then above three phages may be useful for curing staphylococcal infections.

Animals↗
PubMed2004

Homology between two different Salmonella phages: Salmonella enterica serovar Typhimurium phage P22 and Salmonella enterica serovar Anatum var. 15 + phageepsilon34.

A distinguishing feature of many microorganisms, belonging to the Gram negative group of bacteria, is the presence of the lipopolysaccharide on their cell surface. Salmonella is a prominent member of this group of bacteria. Many Salmonella phages use the LPS as the initial receptor in the infection process and they can distinguish subtle changes in the LPS molecules. The phage protein that is responsible for recognition of these cells is the tail or tailspike protein (TSP). Those TSPs, which use LPS as a receptor, are prokaryotic LPS-binding proteins. As an initial step in using phage TSPs as model systems for a detailed molecular genetic analysis of protein-LPS interactions, a comparison of two phages and their TSPs from two different Salmonella bacterial viruses (phages), Salmonella enterica serovar Typhimurium phage P22 and Salmonella enterica serovar Anatum var. 15 + phage epsilon34, is being carried out. This present study shows significant viral protein homology between many viral structural proteins from these two phages including their TSPs. Significantly this report suggests a general structural motif for part of the TSP of phages and suggests that a more detailed comparative analysis of these TSPs is warranted.

Animals↗
PubMed2001

[Autoplaque formation in a Pseudomonas fluorescens strain: phage-like particles and transactivation of the defective phage].

Natural bacteriophages of Pseudomonas fluorescens are rare and its temperate phages have not been described so far. In search for these phages, we have found that one of the P. fluorescens strains forms numerous small transparent autoplaques of different size and shape, which contained material reproducible on the same strains. When centrifuged in a cesium chloride gradient, this material yielded a band in the density zone of about 1.3 g/cm3, where protein components or bacteriophages with a relatively low content of nucleic acid are usually located. In the band material, electron microscopy revealed phagelike particles with empty and mostly undamaged heads and tails carrying in their distal region a formation resembling contracted sheath. DNA isolated from the preparation consisted of two components: a distinct 54-kb fragment, and a diffuse fragment ranging in size from 20 to 9.5 kb. Treatment of the large DNA fragment with various endonucleases yielded 42.2- and 29.5-kb fragments (on average for different endonucleases); whereas the same treatment of the diffuse fragment yielded two- to three distinct fragments with the overall molecular sizes of 8.9 and 6.2 kb (for different nucleases). We have suggested that cells harbor two different genetic elements whose interaction results in the autoplaque appearance and in the formation of negative colonies after infection with the autoplaque material. One of the two elements displays properties of a defective prophage with disturbed DNA synthesis and assembly, whereas the other exhibits the properties of a transposable phage. After complementation or some other interaction between these elements (transactivation, prophage induction caused by repressor inactivation), a bulk of defective phage particles devoid of DNA and a few DNA-containing particles were produced. It remains unclear whether both DNA types are contained in the same or different particles. The phage (or a system of elements) referred to as PT3 is noninducible. The phage mutants forming larger negative colonies (NCs) were also revealed. Some of bacterial mutants resistant to PT3 infection produce the mutant phage with small and turbid NCs. PT3 produces no NCs on the lawns of other strains of the same or other pseudomonade species. This is the first case of describing a natural temperate bacteriophage in P. fluorescens. The two different elements of this phage may represent the same genome of the defective prophage divided into two portions within a bacterial chromosome, each of which is capable of packaging into the phage head.

DNA, Viral↗
PubMed1975

[Results of typing staphylococci isolated from cows and their milk products using the basic set of phages and local phages].

The basic set of phages recommended for typing staphylococci from cattle and also of local phages were approbated. Staphylococci cultures (950 in all) isolated in various regions of the Soviet Union from milk, milk produce and from cows suffering from mastitis were studied. Percentage of cultures typed by the phages of the basic set proved to be 78.3. Thirty different phage patterns were revealed among staphylococcal cultures lysed by phages. Lytic activity was the greatest in phages of group IV of the basic set. It is suggested that local phage 34k can be used as an additional phage permitting to subdivide the prevailing phage types within group IV into a number of new ones.

Animals↗
PubMed1979

[Functional interactions of the genomes of Shigella sonnei phages and Escherichia coli phage T4 in mixed infection].

A comparative study of Shigella sonnei phages U and G and Escherichia coli phage T4 has shown that enzymes coded for by the Sh. sonnei phages can functionally substitute for some T4-coded products. This finding in indicative of an evolutionary relationship between T-even phages and disenteric phages U and G. The U phage is uncapable to compensate amber mutants for the genes that control the conversion of cytosine into 5-hydroxymethyl cytosine (5-HMC) and the glucosylation of the latter, which agrees with our earlier finding that the U phage DNA contains no 5-HMC. U and G phages are also found to exclude the T4 phage in the course of mixed infection.

Bacteriophages↗
PubMed1999

Isolation of chloroform-resistant mutants of filamentous phage: localization in models of phage structure.

Interaction of fd or M13 filamentous phage with a chloroform/water interface induces morphological change, contracting the filaments sequentially into shortened rods (I-forms), and then into spheroidal particles (S-forms). To further investigate this phage contraction, 34 and 26 chloroform-resistant isolates of fd and M13, respectively, were selected after chloroform treatment of wild-type phages at pH 8. 2 and 4 degrees C. DNA sequencing of gene VIII of the 34 fd isolates revealed five different mutants: these were D5H, M28L, V31L, I37T, and S50T. All 26 M13 isolates were I37T. These mutants exhibited variable sensitivity to chloroform, but all contracted much more slowly than wild-type phage during treatment at 4 degrees C. They all contracted like wild-type phage at 37 degrees C. Site-directed mutagenesis showed that the indicated single mutations carried the chloroform resistance. In structural models of the phage, the D5H locus is on the outside and the S50T locus is on the inside. The M28L and I37T loci are buried in a mostly hydrophobic region in the middle. Although these four mutants are spread out radially, they are localized in the axial direction into a thin disk in the model. The last mutant locus, V31L, is out of this disk, but this locus is proximal to the M28L and I37T loci and also in contact with the surface via a deep hydrophobic hole or depression. These five mutants, their locations, and their variable affects on contraction suggest that chloroform-induced contraction involves a specific mechanism rather than a generalized solvent-induced denaturation and that the critical structural changes occur in a localized level in the phage. These results add weight to suggestions that the sequential contraction of filaments-->I-forms-->S-forms mimic corresponding steps in phage penetration, and, in the reverse order, for phage assembly.

Bacteriophage M13↗
PubMed1979

Primary structure of an EcoRI fragment of lambda imm434 DNA containing regions cI-cro of phage 434 and cII-o of phage lambda.

Digestion of phage lambda imm434 DNA with restriction endonuclease EcoRI yields 7 fragments. The shortest among them (1287 bp) contains the right part of the phage 434 immunity region and the phage DNA portion proximal to it. The complete primary structure of this fragment has been determined using the chemical method of DNA sequencing. Hypothetical amino-acid sequences of proteins coded by the cro gene of phage 434 and the cII gene of phage lambda, as well as NH2-terminal amino-acid sequences of the cI protein of phage 434 and the O protein of phage lambda, have been deduced solely on the basis of the DNA sequence. The fragment studied contains also the pR and probably prm promoters and the oR operator of phage 434. The sequence coding for them differs from the respective DNA sequence of phage lambda.

Base Sequence↗
PubMed1994

Monoclonal antibodies that recognise filamentous phage: tools for phage display technology.

We generated six hybridoma cell lines that secrete monoclonal antibodies (mAb) which specifically bind filamentous phage coat proteins. Two of these mAb recognise epitopes that include the N terminus of the coat protein III (pIII), while two others are specific for the N terminus of the major coat protein VIII (pVIII). These mAb are valuable tools to study phage assembly and structure. Furthermore, we describe two examples of how these mAb can be exploited in the construction and screening of peptide libraries displayed by the filamentous phase major coat protein. We have used one of these mAb to develop a sensitive ELISA with crude phage supernatants. This assay allows rapid screening of large numbers of clones from random peptide phage libraries. Some of the anti-phage mAb described here can interfere with wild-type phage propagation, while phage carrying modifications in their coat proteins are insensitive to growth inhibition. We have exploited this observation as a tool to favour the growth of phage displaying peptides fused to pVIII, with respect to vector phage.

Amino Acid Sequence↗
PubMed2003

A morphologic study of filamentous phage infection of Escherichia coli using biotinylated phages.

Using biotinylated phage (BIO-phages), we observed the infection of filamentous phages into Escherichia coli JM109 morphologically. BIO-phages and BIO-phage-derived proteins, mainly pVIII, were detected in E. coli by using the avidin-biotin-peroxidase complex method with electron microscopy. Infected cells revealed positive staining on the outer and inner membranes and in the periplasmic space. Some cells showed specific or predominant staining of the outer membrane, whereas others showed predominant staining of the inner membrane or equivalent staining of the outer and inner membranes. The periplasmic spaces in some infected cells were expanded and filled with reaction products. Some cells showed wavy lines of positive staining in the periplasmic space. BIO-phages were detected as thick filaments or clusters covered with reaction products. The ends of the infecting phages were located on the surface of cells, in the periplasmic space, or on the inner membrane. These findings suggest that phage major coat proteins are integrated into the outer membrane and that phages cause periplasmic expansion during infection.

Biotinylation↗
PubMed1997

Filamentous phage infection-mediated gene expression: construction and propagation of the gIII deletion mutant helper phage R408d3.

We describe the use of transcriptional fusions to the phage shock protein (psp) promoter. These fusions are expressed only when cells are infected by filamentous phage. In an application, the psp promoter was fused to the protein coding part of filamentous phage gene III (gIII). Protein III (pIII) is needed to complement mutant f1 phage containing a deletion of gIII, but its synthesis also renders cells resistant to infection. By inducing pIII production from psp-gIII only in the cells that are already infected with phage, it was possible to obtain plaques from phage in which gIII had been completely deleted. gIII was deleted from two helper phages: R408 and VCSM13, which were then propagated on cells containing the psp-gIII fusion. These two phages were tested for use in a phage display method that requires generation of noninfectious, phagemid-containing virion-like particles. Both helpers worked, but R408d3 was superior to VCSM13d3, because it generated about 1800-times fewer background infectious particles.

Capsid Proteins↗
PubMed2004

Selection of internalizing ligand-display phage using rolling circle amplification for phage recovery.

Selection of phage libraries against complex living targets such as whole cells or organs can yield valuable targeting ligands without prior knowledge of the targeted receptor. Our previous studies have shown that noninfective multivalent ligand display phagemids internalize into mammalian cells more efficiently than their monovalent counterparts suggesting that cell-based selection of internalizing ligands might be improved using multivalently displayed peptides, antibodies or cDNAs. However, alternative methods of phage recovery are needed to select phage from noninfective libraries. To this end, we reasoned that rolling circle amplification (RCA) of phage DNA could be used to recover noninfective phage. In feasibility studies, we obtained up to 1.5 million-fold enrichment of internalizing EGF-targeted phage using RCA. When RCA was applied to a large random peptide library, eight distinct human prostate carcinoma cell-internalizing peptides were isolated within three selection rounds. These data establish RCA as an alternative to infection for phage recovery that can be used to identify peptides from noninfective phage display libraries or infective libraries under conditions where there is the potential for loss of phage infectivity.

Bacteriophages↗
PubMed2002

An improved helper phage system for efficient isolation of specific antibody molecules in phage display.

Phage display technology has been applied in many fields of biological and medical sciences to study molecular interactions and especially in the generation of monoclonal antibodies of human origin. However, extremely low display level of antibody molecules on the surface of phage is an intrinsic problem of a phagemid-based display system resulting in low success rate of isolating specific binding molecules. We show here that display of single-chain antibody fragment (scFv) generated with pIGT3 phagemid can be increased dramatically by using a genetically modified Ex-phage. Ex-phage has a mutant pIII gene that produces a functional wild-type pIII in suppressing Escherichia coli strains but does not make any pIII in non-suppressing E.coli strains. Packaging phagemids encoding antibody-pIII fusion in F+ non-suppressing E.coli strains with Ex-phage enhanced the display level of antibody fragments on the surfaces of recombinant phage particles resulting in an increase of antigen-binding reactivity >100-fold compared to packaging with M13KO7 helper phage. Thus, the Ex-phage and pIGT3 phagemid vector provides a system for the efficient enrichment of specific binding antibodies from a phage display library and, thereby, increases the chance of obtaining more diverse antibodies specific for target antigens.

Amino Acid Sequence↗
PubMed2006

Eliminating helper phage from phage display.

Phage display technology involves the display of proteins or peptides, as coat protein fusions, on the surface of a phage or phagemid particles. Using standard technology, helper phage are essential for the replication and assembly of phagemid particles, during library production and biopanning. We have eliminated the need to add helper phage by using 'bacterial packaging cell lines' that provide the same functions. These cell lines contain M13-based helper plasmids that express phage packaging proteins which assemble phagemid particles as efficiently as helper phage, but without helper phage contamination. This results in genetically pure phagemid particle preparations. Furthermore, by using constructs differing in the form of gene 3 that they contain, we have shown that the display, from a single library, can be modulated between monovalent (phagemid-like) and multivalent display (phage-like) without any further engineering. These packaging cells eliminate the use of helper phage from phagemid-based selection protocols; reducing the amount of technical preparation, facilitating automation, optimizing selections by matching display levels to diversity, and effectively using the packaged phagemid particles as means to transfer genetic information at an efficiency approaching 100%.

Bacteria↗
PubMed1979

Adenosine triphosphate content in Lactobacillus casei and the blender-resistant phage-cell complex-forming ability of cells on infection with PL-1 phage.

The intracellular ATP content of Lactobacillus casei ATCC 27092 grown in a glucose-containing medium was almost constant (2 to 3 microgram/mg dry wt. cells) through the early to middle stage of logarithmic phase, but it was lowered to less than 0.1 microgram/mg after cessation of growth owing to the exhaustion of available glucose. All the cells in the early stage of stationary phase were still viable and thus considered to be in a starved state. When such starved cells were infected with PL-1 phages in a tris-maleate buffer of pH 6.0, the process of forming blender-resistant phage-cell complexes signifying the complete injection of phage genomes into the cells was much inhibited. There was a good correlation between the ATP content of cells and the extent of the formation of blender-resistant phage-cell complexes and the correlation coefficient between them was 0.89 + 0.09 at the 95% confidence limit. On the other hand, the process of forming both the phage-adsorbed cells and the anti-phage serum-resistant phage-cell complexes were not affected by the ATP content of cells. Feeding of glucose to such starved cell cultures caused the cells to restore both the ATP content and the ability to form blender-resistant phage-cell complexes. Such restoration was also observed when the starved cells collected by centrifugation were incubated in a glucose-containing medium. The significance of the intracellular level of high energy compounds such as ATP for the mechanism of the injection of phage genomes into the cells is discussed.

Adenosine Triphosphate↗
PubMed1987

Characterization of Vibrio eltor typing phages: properties of the Eltor phage e4.

Biophysical characteristics of Vibrio eltor phage e4, a key phage in the Vibrio cholerae typing scheme were studied. This icosahedral phage was found to contain 12 structural polypeptides with mol. wt. ranging from 25,000 to 120,000. One of these polypeptides of mol. wt. 50,000 accounted for most of the structural proteins present and was probably the major phage capsid protein. The phage genome comprised a single linear, double-stranded DNA molecule, 69.2 kbp in length (45.6 X 10(6) mol. wt.) as determined by electron microscopy and restriction fragment analyses. The G + C content was 34.6%. Electron microscopy data indicated that unlike the DNAs of other cholera phages, phage e4 DNA is not circularly permuted. Adsorption under normal conditions was biphasic with rate constants of 1.02 X 10(-9)/ml/min up to 60% adsorption and 3 X 10(-10)/ml/min thereafter. Intracellular phage multiplication was characterized by a latent period of 27 min. The burst size was approximately 100 phage particles per infected cell.

Adsorption↗