- Volume 5, Issue 2, 1969
Volume 5, Issue 2, 1969
- Articles
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Host Conversion by Prophage Lambda in a Recombination-deficient Mutant of Escherichia coli
More LessSUMMARYA recombination-deficient (rec −) strain, AB2463, of Escherichia coli K 12 yielded λ lysogens of two types. A rare form, AB2463 (λ)(ind), differed from the usual type, AB2463(λ), in showing ultraviolet (u.v.) irradiation induction of the prophage, forming normal numbers of conjugational recombinants and displaying a u.v. response curve similar to that of the parental rec + strain, AB1157. Superinfection of the inducible form with phage 21b2 led either to loss of the prophage or to the infrequent production of a form which was still lysogenic but no longer inducible. In both cases the bacteria regained their rec − condition as a result of the curing treatment. The phage released from AB2463(λ)(ind) was normal λ. It is concluded that the rec + phenotype of AB2463 (λ)(ind) derives from the presence of the prophage and represents a case of host conversion. It is proposed that AB2463 (λ)(ind) is doubly lysogenic for λ and that partial curing yields the rec − single lysogen AB2463(λ).
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Interconversion of rec + and rec − Phenotype in λ Lysogens of Escherichia coli
More LessSUMMARYWhen a λ-lysogenic recombination-deficient (rec−) mutant of Escherichia coli K 12, AB2463(λ), was superinfected with ultraviolet-irradiated λ in the presence of 6-azauracil, there was found among surviving cells a doubly lysogenic form, AB2463 (λ)(ind), with rec + phenotype. The double lysogen obtained by superinfection of AB2463(λ) with λcI857 ind − displayed a rec − phenotype at 30° and rec + characteristics at 40°. Superinfection of AB2463(λ) with phage 434hy2c+h, which lacks the c region of λ, yielded rec − double lysogens. Since heat inactivation of the repressor in AB2463(λ) (λcI857 ind −) produced a rec + form one of the prophages in AB 2463(λ)(ind) may have been incompletely repressed, hence the expression of its recombination function. For its host?converting effect the superinfecting phage appeared to require the c region of its genome. The results of recombination analysis suggested that in AB2463 (λ)(ind) the first prophage was integrated normally while the second prophage occupied a tandem position more distant than usual, and/or existed in a special relationship conferring on it immunity from or the capacity to overcome the repressor function of the cI product in respect of gene recombination function.
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Electron Microscopic Studies of Rubella Virus
More LessSUMMARYElectron microscopy of BHK-21 and BS-C-1 cells infected with rubella virus revealed spherical particles measuring 50 to 85 nm. in diameter and some elongated forms, predominantly in the budding stage, up to 240 nm. in length. The sequential steps in the development of the virion, beginning with the initial budding stage to the completion of the mature form, were studied. In addition, ferritin-labelled rubella antibodies were used to tag virus particles in various stages of maturation. Surface membranes of infected cells which had undergone antigenic changes without morphological alteration were also tagged; presumably such areas are the sites of haemadsorption of pigeon red blood cells to a seemingly normal-appearing cell membrane. Haemadsorption with and without virus particles functioning as bridges between cells is illustrated.
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The Envelope of Vaccinia and Orf Viruses: an Electron-cytochemical Investigation
More LessSummaryOrf and vaccinia virus preparations adsorbed to carbon coated grids were treated in various ways. Two general patterns of degradation were noted. The particle lost its shape and increased in surface area when the internal envelope disintegrated. When the membranous external envelope was degraded no change in virus size or shape was noted. The range of agents that degraded the external envelope suggests that it is a lipid-protein (probably proteolipid) membrane.
The internal envelope was degraded by treatment with ether followed by trypsin but not by the reverse sequence or by either agent alone. From this and other experiments it was deduced that the internal envelope subunits are protein covered by lipid, the major portion of which is phosphoglyceride and triglyceride. The simplest model of the envelope consistent with the evidence comprises an internal envelope subunit protein associated with the polar ends of a layer of orientated phosphoglyceride molecules whose non-polar parts are in turn associated with a layer of triglyceride molecules. The residual space, bounded by adjacent subunits and by the external envelope, is occupied by cholesterol.
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The Structural and Functional Diversity of Adenovirus Capsid Components
More LessAdenoviruses offer a number of advantages for integrated morphological and functional studies of structural virus components. During the course of multiplication of these viruses structural components are produced in considerable excess. These components are soluble, both in the traditional and in the true sense of the word, and have dimensions which allow their examination by electron microscopy. In addition most of these soluble components can be easily identified by a number of different biological tests.
During the last four years there has been a considerable accumulation of information on structural and biological characteristics of adenovirus capsid components (cf. Norrby, 1968a). This new phase of intensive studies of structural adenovirus components was initiated by the demonstration that vertex capsomeres differed immunologically from non-vertex capsomeres and that they carried projections (Valentine & Pereira, 1965; Norrby, 1966a). In the present article an attempt is made to give a brief summing up of our present state of knowledge in this field.
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The Inactivation of Virus in Cultured Shoot Tips of Nicotiana rustica L.
More LessSUMMARYThree weeks after inoculation, cherry leaf roll virus and arabis mosaic virus were each detected in the apices of at least seven axillary buds above the inoculated leaves of Nicotiana rustica plants. Such infected apices were grown into young plants on Linsmaier and Skoogy’s (1965) medium, and their virus content tested after 14 to 135 days; 50 to 78% were apparently free from cherry leaf roll virus and 69% from arabis mosaic virus. In a more detailed test with cherry leaf roll virus, the proportion of virus-free plants increased from 50% after 16 days to 100% after 108 days. Similar plants grown for 30 weeks remained free of symptoms and detectable virus.
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Serological Reactions of Bovine Diarrhoea Viruses with Anticellular and Antivirus Sera Produced in Rabbits
More LessSummaryRabbit antisera to bovine kidney cells neutralized several naturally occurring strains as well as laboratory modified strains of bovine diarrhoea virus. Antisera to porcine kidney cells failed to neutralize bovine diarrhoea virus even when cultured in porcine kidney cells. These anticellular sera failed to neutralize the viruses of infectious bovine rhinotracheitis, vesicular stomatitis, bovine enterovirus, vaccinia, and parainfluenza-3. Anticellular sera reacted specifically with homologous cells in an indirect immunofluorescent test, but did not form lines of precipitation with cell contents prepared by ultrasonic disruption. These preparations, however, formed multiple lines with antivirus sera, indicating that the antibody produced in rabbits against virus-infected cells differed in some way from the antibody produced in rabbits against whole cells or cell contents.
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A Kinetic Analysis of the Synthesis in BHK 21 Cells of RNAs Specific for Semliki Forest Virus
More LessSummaryA kinetic analysis of formation of Semliki Forest virus-specific RNAs revealed that 22 S RNA was synthesized first and accumulated within or on a structure not disrupted by homogenization, but disrupted by detergent treatment, presumably a lipid-containing membrane or vesicle. When sampled at the end of the latent period of virus growth the 22 S RNA consisted of a mixture of two RNAs, double- and single-stranded. The amount of double-stranded 22 S RNA remained constant thereafter with no complementary RNA synthesized after the latent period of virus growth.
Appearing during the latter portion of the latent period were 26 S RNAs and 42 S virus RNA. The rate at which 26 S RNA accumulated remained constant throughout infection thereafter, whereas that of 42 S virus RNA was maximal at the time of maximal virus accumulation.
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Characterization of Lytic Bacteriophages of Bacilius thuringiensis
More LessSummaryA group of six phages, GV-1 to GV-6, was characterized. These phages use a strain of Bacillus thuringiensis var. galleriae, serotype V, esterase type 5, as host. The phages were divided into three types: Group I, phages GV-1, GV-2 and GV-4; Group II, phages GV-3 and GV-5; Group III, phage GV-6. Their morphology, plaque morphology, host range, serum neutralization, adsorption rates, one-step growth characteristics, calcium requirements, thermal inactivation and stability were examined. Distinction between the groups was clear-cut, and sufficient differences were observed between individual phages within a group to allow differentiation. Group I phages do not resemble any of the phages previously reported as replicating in B. thuringiensis; group II phages resembled the B. subtilis phage GA-1 (Bradley, 1965); GV-6 phage may be similar to a previously reported B. thuringiensis phage (Chapman & Norris, 1966).
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Characterization of Temperate Bacteriophages of Bacillus thuringiensis
More LessSUMMARYEight phages lysogenic for Bacillus thuringiensis var. galleriae which elicit the lytic response in B. thuringiensis var. subtoxicus were isolated by induction of the host strains. We have divided these phages into three groups: group I, phages GT-1 to GT-5; group II, GT-6 and GT-7; group III, GT-8. The following properties of the phages were examined: morphology, host range, serum neutralization, adsorption rates, one-step growth characteristics and thermal inactivation rates. The three groups are readily distinguishable on the basis of morphology and host range. Group II and III show a high degree of homology in regard to their host range, serum neutralization, one-step growth and thermal inactivation characteristics. The phages bear a certain resemblance to previously reported virulent phages of B. thuringiensis (Chapman & Norris, 1966; Colasito & Rogoff, 1969).
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Effect of Temperature on the Multiplication of an Influenza Virus
More LessSummaryThe temperature characteristic of the RNA-dependent RNA polymerase induced after infection with fowl plague virus was determined. At temperatures below 34° the energy of activation in vitro was 16 kcal./mol. greater than above this temperature. The rate of synthesis of virus haemagglutinin and neuraminidase decreased rapidly below 34°. At low temperatures the activity of the virus RNA polymerase may be rate limiting for virus multiplication. At 41° the virus RNA polymerase was unstable in vitro as well as in vivo. The synthesis of virus haemagglutinin and neuraminidase, however, was unimpaired. At 44° virus subunits were not produced. The host cells withstood 44° without any irreversible harm during the time of the experiment. It is uncertain whether or not at elevated temperatures the activity of the viral RNA polymerase was also rate limiting.
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Purification of Encephalomyocarditis Virus
More LessSummaryBy combining the techniques of acid precipitation, organic solvent extraction, enzyme treatment and differential centrifugation, concentration of encephalomyocarditis virus more than 1000-fold with 30% to 50% yield and a degree of purification of more than 1 × 104 was achieved. Yield was estimated by adding virus labelled with 32P to crude virus and measuring the percentage recovery both of the radioactive label and of the total number of plaque forming units in the final product. The degree of purification was determined by adding both 32P-and 3H-labelled, uninfected host-cell material to crude virus and measuring the extent to which the final product was contaminated with radioactive label. Pure virus comprised a homogeneous preparation of polyhedral particles with a particle to plaque forming units ratio of 250 ± 40 and gave a single, symmetrical peak in the analytical ultracentrifuge.
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Induced Ribonucleic Acids in Cells Infected with Vesicular Stomatitis Virus
More LessSummaryRNA molecules labelled in BHK 21 cells following infection with vesicular stomatitis virus in the presence of Actinomycin D and 32PO4 were examined. A complex pattern was obtained when the RNA was centrifuged in sucrose gradients, at least five radioactive peaks being found. These had sedimentation coefficients in sucrose gradients in 0.1 M-sodium acetate, pH 5.0, of approx, 38 S, 28 S, 20 S, 12 S and less than 4 S. Two, 2, 12, 16 and 8% respectively of the radioactive RNA was resistant to ribonuclease 1 μg./ml. Treatment of the unfractionated induced RNA with ribonuclease 1 μg./ml. yielded a product which had a heterogeneous sedimentation profile (7 to 11 S) in sucrose gradients. Recentrifuging individual fractions of this peak in separate gradients confirmed that the ribonuclease-resistant RNA was heterogeneous. The ribonuclease-resistant RNA also gave a heterogeneous profile in caesium sulphate gradients, with a density range of 1.61 to 1.65 g./ml. The induced RNA which sedimented most slowly in the sucrose gradients could be separated from the labelled cellular 4 S RNA by filtration through Sephadex G-75. The base composition of this RNA was significantly different from those of the faster sedimenting induced RNA molecules. Its association with vesicular stomatitis virus infection was confirmed by the failure to detect a similar slowly sedimenting RNA in uninfected cells or in cells infected with foot-and-mouth disease virus.
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Volume 5 (1969)
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Volume 4 (1969)
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Volume 3 (1968)
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Volume 2 (1968)
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Volume 1 (1967)