- Volume 131, Issue 5, 1985
Volume 131, Issue 5, 1985
- Biochemistry
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Mercuric Reductase Enzymes from Streptomyces Species and Group B Streptococcus
Mercury volatilization (Hg2+ reductase) activity has been found with Hg2+-resistant isolates of three Streptomyces species and with three Hg2+-resistant strains of group B Streptococcus from clinical sources in Japan. Hg2+ reductase activities in crude cell extracts showed the temperature sensitivity, the requirement for an added thiol compound and the characteristic dependence on NAD(P)H cofactors of similar enzymes isolated from other bacteria.
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Glutamine Synthetase from Pseudomonas syringae pv. tabaci: Properties and Inhibition by Tabtoxinine-β-lactam
More LessGlutamine synthetase from Pseudomonas syringae pv. tabaci was purified 500-fold. Maximum activity was observed with 10 mm-glutamate, 20 mm-ATP and 4 mm-NH4Cl. The enzyme exhibited substrate inhibition; higher levels of glutamate, Mg. ATP or NH4Cl decreased its activity. The γ-glutamyltransferase activity was inhibited by Mg2+ (75% at 10mm-Mg2+). The enzyme was heat stable and there appeared to be only one form present. Tabtoxinine-β-lactam, a hydrolytic product of tabtoxin produced by pv. tabaci, inactivated the enzyme. This inhibition was linear with respect to the concentration of the inhibitor, and enzyme activity could not be recovered by dialysis, acetone precipitation or incubation with crude cell lysate. Mg. ATP and ammonium ions were required for binding of the inhibitor: incubation of tabtoxinine-β-lactam with the enzyme in the presence of both Mg. ATP and ammonium ions resulted in a greater decrease in synthetase activity than incubation with either one or neither component. Tabtoxinine-β-lactam did not inhibit the γ-glutamyltransferase activity of the enzyme if ADP was used in the assay, but did when ATP was used.
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Preliminary Characterization of an Antibiotic Produced by Xanthomonas albilineans Which Inhibits DNA Synthesis in Escherichia coli
More LessChlorosis-inducing isolates of Xanthomonas albilineans, the sugarcane leaf scald pathogen, produced a mixture of antibacterial compounds in culture. The antibiotic mixture, which eluted as a single strongly retarded peak from Sephadex LH-20 in methanol, was bactericidal to Escherichia coli. Inhibition of E. coli was not reversed by added nutrients, and affected cells were not lysed but many accumulated polyphosphate granules. The major antibacterial component, isolated in crystalline form after HPLC, is given the trivial name albicidin. Near the minimum inhibitory concentration, albicidin caused a complete block to DNA synthesis, followed by partial inhibition of RNA and protein synthesis, as assessed by incorporation of radioactive precursors. Spontaneous antibiotic-resistant mutants of E. coli showed no cross-resistance between albicidin and inhibitors of either subunit of DNA gyrase. Mixing albicidin with purified DNA from E. coli did not alter the thermal denaturation behaviour of the DNA, or the absorption spectrum of the antibiotic. PolA+ and PolA– strains of E. coli were equally sensitive to albicidin. indicating that the antibiotic does not bind to or modify DNA. Selective inhibition of DNA synthesis without evidence of DNA binding suggests a specific interaction of albicidin with an essential replication protein.
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- Development And Structure
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Immunogold Localization of p55-Fibril Protein and p25-Spiralin in Spiroplasma Cells
More LessTransmission electron microscopy of thin sectioned cells of the honeybee spiroplasma BC3 revealed evidence of a helically twisted ribbon closely associated with the cytoplasmic surface of the plasma membrane. The cellular distribution of p55-fibril protein as demonstrated by immunogold staining with anti-p55 antibody was consistent with the presence of p55 in this ribbon. We conclude that spiroplasma fibrils are arranged in a single helically twisted ribbon rather than forming a contractile sheath or branched axial fibre. Immunogold staining with anti-p25-spiralin antibody confirmed that this protein is localized in the plasma membrane and also showed that it occurs in extracellular strands. These strands may be antigenically distinct from the integral form of the protein.
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Induction of Spheroplasts in Capnocytophaga ochracea
More LessA gentle technique for preparing spheroplasts of Capnocytophaga ochracea strain 25 is described. Cells in the exponential phase were washed with 1·0 m-NaCl, agitated in 1·0 m-NaCl for 2 h at 30°C and exposed to lysozyme in a Tris/salts buffer, pH 7·0. This procedure resulted in 98% spheroplast formation with complete removal of the peptidoglycan layer as detected by both phase-contrast and electron microscopy in combination with chemical analysis.
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Ultrastructure of Bacilli and the Bacillary Origin of the Macrophagic Inclusions in Whipple’s Disease
More LessAn electron microscopic and cytochemical study of the Whipple bacillus in jejunal biopsies from three untreated patients was made using fixation procedures developed for the satisfactory preservation of bacterial ultrastructure. The envelopes of the normal- looking bacilli present free in the lamina propria consisted of the following layers. (i) A cytoplasmic membrane with a triple-layered profile and a mean thickness (peak-to- peak distance) of 6.08 nm. (ii) A thick (20 nm) cell wall containing peptidoglycan; the wall had a hitherto undescribed inner layer that contained polysaccharides, possibly teichoic acids. (iii) Surrounding the cell wall, a surface membrane with a symmetric profile and a mean peak-to-peak distance of 4.74 nm. The ultrastructural pattern of the Whipple bacillus wall corresponds to that of Gram- positive bacteria, but with an additional surface membrane. This membrane is different from the outer membrane of Gram- negative bacteria because it has a symmetric profile, is thinner and has no periodic acid-Schiff (PAS)-positive components.
Normal-looking bacilli were seen very rarely inside jejunal macrophages, but degenerating bacteria were abundant in these phagocytes. Electron microscopy and ultrastructural cytochemistry of Whipple bacilli inside jejunal macrophages of the three untreated patients showed that the degenerative process is a sequence that leads to the loss of bacillary forms and to the accumulation of bacterial remnants resistant to degradation by the macrophage. These remnants correspond to the innermost, polysaccharide-containing portion of the bacillus wall. The progressive accumulation of these PAS-positive wall remnants is the origin of the intramacrophagic inclusions that are important in the histological diagnosis of Whipple’s disease. The reported results indicate that in the three patients studied, the Whipple bacillus multiplies extracellularly, the bacteria that are phagocytosed by macrophages being degraded.
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- Ecology
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The Effects of Wall Populations on Coexistence of Bacteria in the Liquid Phase of Chemostat Cultures
More LessWe have examined the effects of wall populations on coexistence between strains of Escherichia coli in the liquid phase of mixed (two-strain) chemostats. The wall populations of the two competing strains became established soon after the start of the cultures and, although the relative abundance of the strains in the liquid phase could change over time by several orders of magnitude, the composition of an established wall population did not change markedly. The bacterial strains examined could not displace an established wall population of a competing strain. The presence of a permanent wall population allowed a strain that was less fit in the liquid phase to coexist with a superior strain. The resulting coexistence did not require that the inferior strain attached to the vessel wall better than the superior strain. We believe that the coexistence developed because the inferior strain survived and reproduced on the vessel wall. The progeny from that wall population then provided replacements for the bacteria that the inferior strain lost through a selective disadvantage in the liquid phase of the culture. By replacing the chemostat vessel, hence eliminating the wall populations, we could distinguish between cases where the coexistence depended on the presence of a wall population and where it resulted from some alternative mechanism.
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The Barrier-Ring Plate Technique for Studying Extracellular Enzyme Diffusion and Microbial Growth in Model Soil Environments
More LessA novel technique has been developed to study complex spatial interactions between microorganisms, enzymes and their substrates in soil using barriers composed of soil and soil components inserted into agar plates. This has allowed the investigation of extracellular enzyme diffusion and microbial growth through soil-like but carefully controlled environments. Using ‘barrier-ring plates’ the effects of small quantities of soil and various soil components on endoglucanase and β-d-glucosidase diffusion was shown. Bentonite, with a relatively high unit surface area and a high cation exchange capacity, reduced the distance diffused by both enzymes. Kaolinite, a clay with a relatively low unit surface area and a low cation exchange capacity, had no effect while the colloidal-size (<2 μm) clay-humic fraction separated from a silt loam soil reduced the distance diffused by endoglucanase by an amount intermediate between that of kaolinite and bentonite. The same barrier-ring plate technique was used to demonstrate how soil components differentially affect the radial growth of a cellulolytic Streptomyces sp. and Trichoderma υiride, T. koningii and Botryotrichum piluliferum.
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Agrobacterium rhizogenes Promotes the Initial Growth of Bare Root Stock Almond
More LessBare root stock almond trees treated with Agrobacterium rhizogenes 232 had a larger root number and root mass after 90 d than those treated with autoclaved or filter-sterilized bacterial suspensions, or with medium alone. Treatment with A. rhizogenes 232 also led to significant increases in leaf number, stem diameter and shoot elongation during the first growing season after treatment. The bacterium was recoverable from both the rhizosphere and the bulk soil around the treated roots, but never from uninoculated control roots. Thus, the reaction of almond to A. rhizogenes was not a pathological one even though this bacterium is classified as a pathogen.
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- Genetics And Molecular Biology
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Nucleotide Sequence and Complementation Analysis of a Polycistronic Sporulation Operon, spoVA, in Bacillus subtilis
P. FORT and J. ERRINGTONWe have determined the nucleotide sequence of a 3706 bp stretch of Bacillus subtilis chromosomal DNA that complements all known spoVA mutations. The sequence contains five consecutive large open reading frames capable of encoding proteins of molecular weights ranging from approximately 15000 to 36000. Analysis using integrational plasmids suggests that the region is likely to be transcribed as a single mRNA. A novel form of complementation analysis, based on derivatives of bacteriophage ϕ105 carrying the cloned spoVA locus, has been used to define four distinct complementation groups among the eight previously characterized spoVA mutations. The spoVA locus is the largest polycistronic sporulation operon yet characterized.
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Lysis of Escherichia coli by Cloned ϕX174 Gene E Depends on its Expression
U. BLÄSI, B. HENRICH and W. LUBITZThe lysis gene E of bacteriophage ϕX174 was cloned under transcriptional control of the lefthanded lambda promoter, giving rise to plasmid pSB12. Plasmid pSB22, identical to pSB12 except for an amber mutation in gene E, was constructed in the same way. Induction of the cloned wild-type gene by heat inactivation of the thermosensitive λ cI857 repressor resulted in lysis of the host bacteria. With plasmid pSB22 only amber suppressor strains of Escherichia coli lysed after heat inactivation of λ cI857. Lysis of E. coli was shown to depend on the rate of gene E translation and on the growth phase of the bacteria. Stationary cells could not be lysed by the gene E product (gpE), even if present in sufficient amounts to lyse growing cells. By isotopic labelling gpE could be detected among the proteins synthesized in normal E. coli as well as in minicells. Determination of gene E expression suggested that gpE synthesis is translationally regulated.
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Phage pilHα: a Phage Which Adsorbs to IncHI and IncHII Plasmid-coded Pili
Phage pilHα was specific for bacterial strains, of various genera, harbouring plasmids of the HI and HII incompatibility groups. Plaque formation was temperature sensitive in that plaques formed at 26°C but not at 37°C. Plaques were fairly clear, irregular in outline and varied from pin point to about 2 mm in diameter on all hosts where plaques were detected. The phage had an isometric hexagonal outline with a diameter of 25 nm. It contained RNA but differed from all but one other plasmid-dependent RNA phage by being sensitive to chloroform. It adsorbed along the length of the shafts of IncHI and HII plasmid-coded pili.
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Evolution of Tn21-related Transposons: Isolation of Tn2425, which Harbours IS161
More LessThe isolation of two multi-resistance transposons, Tn2425 and Tn1831, and their relation to Tn21 and Tn2424, is described. A 1·7 kb segment present in Tn2424 and Tn2425 was identified as an IS element by rec-independent transposition, resulting in a Cointegrate structure that carries two direct repeated copies of the IS element. By the isolation of this IS element we demonstrated that transposition is one mechanism leading to sequence variations in Tn21-like structures, especially in the region between the mer operon and the sul gene.
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Plasmid Fusions Mediated by One End of TnA
More LessWe have observed plasmid fusions in a recA background mediated by a single end of TnA. These occur when transposase is provided either in cis or in trans. Insertions of the plasmid carrying the TnA inverted repeat sequence occur at many sites in the target plasmid. The point of fusion on the plasmid carrying TnA sequences always appears to be located in the region which carries the TnA inverted repeat sequence. In contrast to the transposition of an intact TnA element, plasmid fusions mediated by one end of TnA are very rare events. The implications of our results for models of transposition are discussed.
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Mutagenesis of a Rhizobium Plasmid Carrying Hydrogenase Determinants
More LessTransposon Tn5-mob, a Tn5 derivative containing the mobilization site of plasmid RP4, was introduced into Rhizobium leguminosarum strain 128C53 on the suicide vector pSup5011. Transposon insertions into the plasmids of strain 128C53 were selected after mating the mutagenized population with a non-nodulating R. leguminosarum recipient. In this way, a tenfold enrichment was effected for plasmid-linked mutations. Transconjugants that had received mutagenized symbiotic plasmids were applied individually to the roots of pea seedlings and, after three weeks, the resulting nodules were screened for the absence of hydrogenase activity. Eight hydrogenase-deficient (Hup–) mutants of R. leguminosarum strain 128C53 were isolated. Physical and genetic analyses suggest that each Hup– mutant was due to a single insertion of Tn5-mob into the symbiotic plasmid, pRL6JI. All mutations were suppressible by pHU1, a cosmid clone carrying some of the hup genes of Rhizobium japonicum.
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Inhibitory Reactions between Natural Isolates of Streptomyces
More LessNine different strains of Streptomyces (‘S. scabies’) have been isolated from scab lesions on potato tubers. These strains were obtained from different cultivars grown in different geographical areas. Four different types of inhibitory reactions were observed when these strains were tested in pairs with each other. Three of these inhibitory reactions resembled the lethal zygosis phenotype that has been reported for other species of Streptomyces. All of the strains exhibited at least two of these inhibitory reactions and were sensitive to the inhibitory reactions of at least six of the other isolates. Five of these isolates were shown to harbour plasmid DNA.
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Structural Organization of a Hypermethylated Nuclear DNA Component in Physarum polycephalum
More LessDigestion of Physarum polycephalum nuclear DNA using the restriction endonuclease HpaII generates two components, distinguishable on the basis of their molecular size. The high-molecular-weight, HpaII-resistant component, which accounts for 20% of the DNA, contains a fivefold greater concentration of 5-methylcytosine residues than the low-molecular-weight HpaII-digested fraction. Segments of hypermethylated (M+) DNA are largely composed of a single, long, highly repeated sequence, and this major element is sometimes associated with other less highly repetitive sequences in the M+ DNA fraction. Restriction mapping of cloned Physarum M+ DNA segments, and Southern blot analysis of genomic DNA using subcloned segments of M+ DNA as a probe, provide evidence for sequence variation within different copies of the dominant highly repeated element, and possibly the other associated repeats in M+ DNA, and additionally that almost complete tandemly repeated copies of the major repeat are found in some M+ DNA segments.
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The Effect of Ploidy on the Stability of Plasmodial Heterokaryons in Physarum polycephalum
More LessThe stability of actively growing heterokaryons made by fusing haploid and diploid plasmodia of Physarum polycephalum has been investigated with the aid of genetic markers affecting plasmodial colour and amino acid requirements. All heterokaryons initially expressed the dominant alleles present in both component plasmodia, but after a few subcultures every heterokaryon synthesized from a haploid plus a diploid plasmodium changed to express the recessive alleles carried by the haploid component. In contrast, heterokaryons synthesized from combinations of haploid plasmodia remained stable throughout many subcultures. No evidence was found for the segregation of incompatibility alleles responsible for heterokaryon instability, although the possibility could not be excluded that a gene closely linked to mat A was involved. A direct test of the effect of ploidy on heterokaryon stability was carried out, in which the use of isogenic haploid and diploid plasmodia allowed the effect of incompatibility genes to be eliminated. Again the phenotype of every haploid plus diploid heterokaryon changed to that of the haploid component, whereas haploid plus haploid heterokaryons remained stable. Variations in the relative sizes of the haploid and diploid plasmodia altered the speed, but not the direction, of the changes observed. Analysis of progeny indicated that the changes in phenotype were due to loss of diploid nuclei from the heterokaryons.
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Genetic Analysis in Streptomyces chrysomallus
More LessA circular linkage map was developed for Streptomyces chrysomallus, a producer of actinomycin C. The map order of various marker loci was deduced from matings and to a minor extent from protoplast fusions. The map strongly resembles that of Streptomyces coelicolor A3(2). The recombination frequencies were low and highly variable (from 10–9 to 5 × 10–6). Plasmid pIJ303 expressed its thiostrepton resistance gene in S. chrysomallus but did not promote chromosomal transfer or induce the Ltz+ phenotype. The data provide a background of genetics for investigations of antibiotic synthesis in this strain.
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Stability of a Catabolic Plasmid in Continuous Culture
More LessA wild-type strain of Pseudomonas putida PPK1, carrying a non-conjugative TOL plasmid, was grown in continuous culture under carbon-limitation with m-toluate as growth substrate. When the medium was changed to benzoate a plasmid-free strain appeared after about 100 h. After this event the proportion of plasmid-containing bacteria declined rapidly but in several experiments this was followed by oscillations in the relative frequencies of the plasmid-free and plasmid-containing populations. About 1% of the total population retained the plasmid after 600 h growth under benzoate-limitation. When the input medium was returned to m-toluate the plasmid-free bacteria disappeared and the TOL+ population recovered to 100%. The plasmid in the wild-type strain was stably maintained during 500 h of chemostat growth under succinate-limitation. TOL+ strains re-isolated from continuous culture under benzoate-limitation retained their TOL plasmids for longer periods. It is suggested that plasmid loss is related to a failure in the control of partitioning at cell division but that this is not absolute and allows the maintenance of a residual low level of plasmid-containing bacteria in the population.
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Isolation of kdgK-lac and kdgA-lac Gene Fusions in the Phytopathogenic Bacterium Erwinia chrysanthemi
More LessErwinia chrysanthemi is a species of enterobacteria whose phytopathogenicity is mainly due to its pectinolytic activity. Pectin degradation leads to the formation of 2-keto-3-deoxygluconate which is catabolized via the kdgA and kdgK gene products. Mutants of Er. chrysanthemi containing genetic fusions of the kdgK or kdgA genes to the lacZ gene of Escherichia coli were isolated by infection of a lacZ mutant of Er. chrysanthemi with the phage Mu d(Ap lac). In these fusion strains, the absence of growth on galacturonate, glucuronate and polygalacturonate, and also β-galactosidase expression, are caused by a single Mu d(Ap lac) insertion. Synthesis of β-galactosidase in these strains was induced in the presence of galacturonate, glucuronate, polygalacturonate or some intermediates of the catabolism of these sugars in the culture medium; synthesis of β-galactosidase was not sensitive to glucose repression.
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Production of Recombinants after Protoplast Fusion in Clostridium acetobutylicum P262
More LessProtoplast fusion of Clostridium acetobutylicum P262 auxotrophs produced stable recombinants and segregating biparentals at frequencies of 0·3–2·0% and 1·4–8·3% respectively. Two novel classes of biparentals, partially-complementing and zero non-complementing, were observed.
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- Immunology
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Identification of an Agent in Cultures of Aspergillus fumigatus Displaying Anti-phagocytic and Immunomodulating Activity in vitro
More LessWhen cultured in vitro, Aspergillus fumigatus generated a metabolite(s) with anti-phagocytic activity as tested by macrophage adherence to plastic and phagocytosis of particulate matter. The metabolite(s) appeared after 3 d culture and reached a peak concentration after 5–6 d. The action of the anti-phagocytic agent(s) was rapid (5–15 min) and appeared not to alter membrane permeability or cause rapid cell death. Treatment of stimulator spleen cells with the agent(s) inhibited their ability to induce alloreactive and major histocompatibility complex restricted cytotoxic T cells. The metabolite(s) was chloroform-soluble and separated into three biologically active compounds on thin-layer chromatography. These compounds were purified > 1000-fold and one of them was identified as gliotoxin, a known metabolite of A. fumigatus, based upon NMR and IR spectroscopy, mass spectrometry, biological properties and other data.
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- Pathogenicity And Medical Microbiology
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A Comparison of Phospholipase Activity, Cellular Adherence and Pathogenicity of Yeasts
More LessPhospholipase A and lysophospholipase activities were measured in the culture fluid and in the blastospores of Candida albicans. When phospholipase activity was measured in six yeasts (four strains of C. albicans and a single strain each of Candida parapsilosis and Saccharomyces cereυisiae) a correlation was found between this activity and two potential parameters of pathogenicity. The C. albicans isolates which adhered most strongly to buccal epithelial cells and were most pathogenic in mice had the highest phospholipase activities. Non-pathogenic yeasts, including C. albicans isolates which did not adhere and did not kill mice, had lower phospholipase activities.
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- Physiology And Growth
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Regulation of ‘Conditional’ Aerial Mycelium Mutants of Streptomycetes
More LessHickey–Tresner agar was originally developed to yield large amounts of aerial mycelium and spores with a variety of Streptomyces strains. Two mutant strains, S. coelicolor M110 and S. alboniger 504, behaved unusually when grown on this medium in that no aerial mycelium was formed. With the former strain, abundant formation of aerial mycelium and spores was found on other media. These variants have been defined as being aerial mycelium-conditional, because the absence or presence of wild-type morphology is dependent on the type of growth medium. This defect is due to the formation and excretion of excess acid and can be reversed by raising the pH above 7 either by growing certain aerial mycelium- negative strains of streptomycetes or Sarcina lutea near these variants, by raising the pH with a suitable buffer or, in the case of S. coelicolor M110, by adding exogenous adenine.
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A New Class of TOL Plasmid Deletion Mutants in Pseudomonas putida MT15 and Their Reversion by Tandem Gene Amplification
More LessPseudomonas putida MT15 contains a large plasmid, pWW15, of about 250 kbp, which encodes the genes for toluene and xylene catabolism. Growth on benzoate selects strongly against the wild-type and results in the segregation of three phenotypically distinguishable mutant types. (1) B1 mutants, which have lost the complete plasmid. (2) B3 mutants, in which the plasmid has undergone a large deletion of about 90 kbp which appears to affect the regulation of the catabolic enzymes; these mutants retain the ability to grow on m-xylene and toluene (Mxy+ Tln+) but no longer grow on the metabolite of m-xylene, m-toluate (Mtol–). (3) A novel class not previously described, the B5 mutants, which still grow well on toluene but grow very poorly on m-xylene and do not grow on m-toluate (Mxy– Tln+ Mtol–). The B5 mutants appear to share the regulatory lesion of the B3 mutants but in addition do not express the xylF and xylG gene products, 2-hydroxymuconic semialdehyde hydrolase and 2-hydroxymuconic semialdehyde dehydrogenase. The plasmids in the B5 mutants have also undergone a deletion of about 90 kbp similar to, but distinguishable from, that in the B3 mutants.
Both B3 and B5 mutants can revert to growth on m-toluate. The revertants all show elevated constitutive levels of catechol 2,3-oxygenase, 2-hydroxymuconic semialdehyde dehydrogenase and 2-hydroxymuconic semialdehyde hydrolase which are not further induced by m-toluate. The reversion is accompanied by the tandem amplification of a region of 23–28 kbp on either side of the original deletion. As a result of Southern hybridizations, it was shown that the amplified region contains the structural genes of some of the enzymes which metabolize m-toluate but not the enzymes which convert m-xylene to m-toluate.
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Critical Parameters in the Isolation of Mitochondria from Candida utilis
More LessThe successive steps in the isolation of mitochondria from chemostat-grown Candida utilis have systematically been investigated for their effects on organelle integrity.Growth rate had a profound effect on the susceptibility of carbon-limited cells towards Zymolyase, whereas the nature of the carbon source had no effect. Stabilization of spheroplasts with at least 2m-sorbitol was required to prevent premature lysis. This was concluded from the amounts of glucose-6-phosphate dehydrogenase liberated during Zymolyase treatments. The influence of the method for disruption of spheroplasts on the quality of the mitochondria was analysed with particular emphasis on respiratory control values and the distribution of marker enzymes among the cell fractions. Disruption by osmotic shock resulted in mitochondria without respiratory control and a high degree of solubilization of NADH and NADPH dehydrogenase activities. Only a gradual decrease of the osmotic value of the medium, preferably by dialysis against a hypotonic buffer, in combination with mechanical disruption with a Potter–Elvehjem homogenizer yielded mitochondria with high respiratory control values and a high retention of NADH dehydrogenase in the organelle. It is concluded that, for the quality of mitochondrial preparations from yeasts, the distribution of NADH dehydrogenase among the cell fractions is a more reliable measure than that of the usual marker enzymes.
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Oxidation of NADH and NADPH by Mitochondria from the Yeast Candida utilis
More LessMitochondria were isolated from Candida utilis CBS 621 grown in carbon-limited continuous cultures on glucose, gluconate, xylose, ethanol or acetate as the carbon source and ammonia or nitrate as the nitrogen source. In all cases mitochondria were isolated which could oxidize exogenous NADH and NADPH via a cyanide- and antimycin A-sensitive but rotenone-insensitive respiratory chain. Oxidation of NADH and NADPH was coupled to energy conservation as evidenced by high respiratory control values. Different respiratory control values of mitochondria with NADH and NADPH as well as variations in the ratio of NADH and NADPH oxidase activities indicate that separate systems exist for the oxidation of exogenous redox equivalents by mitochondria of C. utilis.
Variation of the NADPH requirement for biomass formation by applying different growth conditions did not result in significant changes in NADPH oxidase activities of mitochondria. It is concluded that in C. utilis NADPH can be used in dissimilatory processes for the generation of ATP.
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Subcellular Localization of d-Glucanases in Bacteroides oralis Ig4a
More LessThree d-glucan-hydrolysing enzymes from Bacteroides oralis Ig4a have been isolated. Two of them are dextranases which hydrolyse (1→6) but not (1→3) linked α-d-glucans; one (EC 3.2.1.11,1,6-α-d-glucan 6-glucanohydrolase) is localized in the periplasm, and the other, which is an exo-enzyme (EC 3.2.1.70,1,6-α-d-glucan glucohydrolase), in the cytoplasm. The third is a mutanase (EC 3.2.1.59, 1,3-(1,3;1,4)-α-d-glucan 3-glucanohydrolase) that hydrolyses (1→3) but not (1→6) linked α-d-glucans, and is present only in the cytoplasm.
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A Salmonella typhimurium Strain Defective in Uracil Catabolism and β-Alanine Synthesis
More LessA selection procedure for uracil catabolism mutant strains involving indicator dye plates was developed. Using this method, a strain defective in uracil catabolism has been isolated in Salmonella typhimurium that was temperature-sensitive at 42°C where it required low concentrations of N-carbamoyl-β-alanine, β-alanine or pantothenic acid for growth. An extract of the mutant strain degraded uracil at 37°C at a significantly diminished rate compared to that observed for the wild-type strain under the same growth conditions. The conversion of dihydrouracil to N-carbamoyl-β-alanine was blocked at all temperatures examined in the mutant strain. By means of genetic analysis, the mutant strain was determined to be defective at two genetic loci. Transduction studies with bacteriophage P22 indicated that the panD gene is mutated in this strain, accounting for its β-alanine requirement. Episomal transfers between Escherichia coli and the mutant strain provided evidence that the defect in uracil catabolism was located in another region of the S. typhimurium chromosome.
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- Systematics
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Nucleic Acid Relationships among the Anaerobic Mycoplasmas
More LessThe genetic relatedness between twelve selected strains among four distinct serovars of anaerobic mycoplasmas was studied using [3H]DNA–DNA hybridization, and the results were compared with data obtained from biochemical and serological tests. Radiolabelled DNA probes were prepared from five strains representing four serovars. Based on the homology results, the anaerobic mycoplasmas can be divided into five distinct groups representing five distinct species and two distinct genera. There are two species in the Anaeroplasma bactoclasticum serovar 1 group represented by strains JR and A-2, one species in serovar 2, one species in A. abactoclasticum serovar 3 and one among the unclassified serovar 4 anaerobic mycoplasmas. The probe to nonsterol-requiring strain 161 of serovar 4 showed no homology with any of the established nonsterol-requiring Acholeplasma species DNAs, or with Mycoplasma hominis DNA, or with avian DNA which served as a negative control. There was good correlation between the phenotypic and genotypic properties of the five distinct anaerobic mycoplasma species but the results indicate that phenotypic properties are not always adequate for speciation of the anaerobic mycoplasmas.
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- Short Communication
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The Genome of Bacillus subtilis Phage SPP1: Structure of an Early Promoter
More LessThe strongest of five ‘early’ promoters of Bacillus subtilis phage SPP1 was localized in a DNA restriction fragment by analysis of RNA polymerase binding and R-loop formation. The nucleotide sequence of the promoter region was established. The signal structures identified were similar to those recognized by the σ 55 RNA polymerase of B. subtilis. The promoter precedes an open reading frame with 51 codons. A protein with the M r predicted from the nucleotide sequence was identified in minicells.
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Organization of Fimbriate Cells in Colonies of Escherichia coli Strain 3040
More LessImmunofluorescence staining with fimbria- specific antibodies was used to study the organization of fimbriate cells in colonies of Escherichia coli strain 3040. The strain has both type-1 and S fimbriae and shows fast phase variation between the fimbrial types. Colonies stained in sectors whose length and number per colony were dependent on the fimbrial phase of progeny cells. It is proposed that such sectors result from fimbrial phase variation.
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Volume 136 (1990)
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Volume 135 (1989)
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Volume 134 (1988)
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Volume 133 (1987)
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Volume 132 (1986)
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Volume 131 (1985)
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Volume 130 (1984)
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Volume 129 (1983)
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Volume 128 (1982)
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Volume 127 (1981)
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Volume 126 (1981)
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Volume 125 (1981)
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Volume 124 (1981)
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Volume 123 (1981)
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Volume 122 (1981)
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Volume 121 (1980)
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Volume 120 (1980)
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Volume 119 (1980)
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Volume 118 (1980)
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Volume 117 (1980)
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Volume 116 (1980)
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Volume 115 (1979)
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Volume 114 (1979)
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Volume 113 (1979)
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Volume 112 (1979)
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Volume 111 (1979)
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Volume 110 (1979)
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Volume 109 (1978)
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Volume 108 (1978)
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Volume 107 (1978)
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Volume 106 (1978)
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Volume 105 (1978)
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Volume 104 (1978)
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Volume 103 (1977)
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Volume 102 (1977)
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Volume 101 (1977)
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Volume 100 (1977)
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Volume 99 (1977)
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Volume 98 (1977)
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Volume 97 (1976)
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Volume 96 (1976)
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Volume 95 (1976)
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Volume 94 (1976)
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Volume 93 (1976)
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Volume 92 (1976)
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Volume 91 (1975)
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Volume 90 (1975)
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Volume 89 (1975)
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Volume 88 (1975)
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Volume 87 (1975)
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Volume 86 (1975)
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Volume 85 (1974)
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Volume 84 (1974)
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Volume 83 (1974)
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Volume 82 (1974)
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Volume 81 (1974)
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Volume 80 (1974)
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Volume 79 (1973)
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Volume 78 (1973)
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Volume 77 (1973)
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Volume 76 (1973)
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Volume 75 (1973)
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Volume 74 (1973)
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Volume 73 (1972)
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Volume 72 (1972)
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Volume 71 (1972)
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Volume 70 (1972)
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Volume 69 (1971)
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Volume 68 (1971)
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Volume 67 (1971)
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Volume 66 (1971)
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Volume 65 (1971)
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Volume 64 (1970)
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Volume 63 (1970)
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Volume 62 (1970)
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Volume 61 (1970)
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Volume 60 (1970)
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Volume 59 (1969)
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Volume 58 (1969)
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Volume 57 (1969)
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Volume 56 (1969)
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Volume 55 (1969)
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Volume 54 (1968)
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Volume 53 (1968)
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Volume 52 (1968)
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Volume 51 (1968)
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Volume 50 (1968)
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Volume 49 (1967)
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Volume 48 (1967)
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Volume 47 (1967)
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Volume 46 (1967)
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Volume 45 (1966)
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Volume 44 (1966)
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Volume 43 (1966)
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Volume 42 (1966)
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Volume 41 (1965)
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Volume 40 (1965)
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Volume 39 (1965)
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Volume 38 (1965)
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Volume 37 (1964)
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Volume 36 (1964)
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Volume 35 (1964)
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Volume 34 (1964)
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Volume 33 (1963)
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Volume 32 (1963)
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Volume 31 (1963)
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Volume 30 (1963)
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Volume 29 (1962)
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Volume 28 (1962)
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Volume 27 (1962)
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Volume 26 (1961)
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Volume 25 (1961)
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Volume 24 (1961)
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Volume 23 (1960)
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Volume 22 (1960)
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Volume 21 (1959)
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Volume 20 (1959)
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Volume 19 (1958)
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Volume 18 (1958)
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Volume 17 (1957)
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Volume 16 (1957)
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Volume 15 (1956)
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Volume 14 (1956)
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Volume 13 (1955)
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Volume 12 (1955)
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Volume 11 (1954)
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Volume 10 (1954)
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Volume 9 (1953)
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Volume 8 (1953)
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Volume 7 (1952)
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Volume 6 (1952)
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Volume 5 (1951)
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Volume 4 (1950)
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Volume 3 (1949)
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Volume 2 (1948)
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Volume 1 (1947)