- Volume 130, Issue 7, 1984
Volume 130, Issue 7, 1984
- Biochemistry
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Properties and Role of Sulphite: Cytochrome c Oxidoreductase Purified from Thiobacillus versutus (A2)
More LessSulphite: cytochrome c oxidoreductase (sulphite dehydrogenase) was purified 2000-fold from Thiobacillus versutus (A2). The enzyme monomer had a molecular weight of 44000 and a pI value of 4·5 α 0·3. Cytochrome c 551 was intimately associated with the enzyme: separation of the two greatly decreased sulphite dehydrogenase activity, which was not restored by remixing them. The enzyme had a pH optimum around pH 8·0, exhibited a K m of 14 µm for sulphite, and was inhibited noncompetitively by phosphate, with a K i value of 12 mm. It was also inhibited by p-hydroxymercuribenzoate and cyanide. Its involvement in the oxidation of thiosulphate in T. versutus is discussed.
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Effect of Nitrogen Source on Lipid Accumulation in Oleaginous Yeasts
More LessThe effect of various nitrogen sources on lipid accumulation by 17 species and strains of yeast was examined. Organic nitrogen sources resulted in considerably increased lipid contents only in strains of Rhodosporidium toruloides. Lipid accumulation in Rs. toruloides CBS 14 increased from 18% (w/w), with NH4Cl as nitrogen source, to above 50% (w/w) when glutamate, urea or arginine was used. Stimulation of lipid production by glutamate was not observed when the yeast was grown in continuous culture with nitrogen-limiting medium. The increase in lipid content of glutamate-grown cells in batch culture was accompanied by a marked increase in the intracellular citrate concentration and its excretion from the cells. The pattern of citrate accumulation in glutamate-grown cells was mirrored by the accumulation of other metabolites, especially 2-oxoglutarate and NH+ 4 ions, which were produced as a result of the increased catabolism of glutamate. It is proposed that the products of glutamate metabolism in Rs. toruloides play a major role in regulating the flux of carbon to precursors of lipid biosynthesis, such as citrate.
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Influence of Nitrogen Metabolism on Lipid Accumulation by Rhodosporidium toruloides CBS 14
More LessRhodosporidium toruloides CBS 14 was grown in batch culture with urea as principal nitrogen source. The lipid content increased from 18% (w/w) with NH+ 4-grown cells to 52% (w/w) after 90 h growth. Urea was rapidly taken up and catabolized to release intracellular NH+ 4, which accumulated between 10 and 30 h growth. The increase in pool NH+ 4 content was mirrored by an increase in citric acid accumulation and excretion from the cells. The production of intracellular NH+ 4, sufficient to permit lipid accumulation, could be attributed to the increase in activity of urease over this period. Similarly, other catabolic enzymes, such as arginase, threonine dehydratase and NAD+: glutamate dehydrogenase, were also induced (or derepressed) when the respective amino acids were used as medium nitrogen source. Growth with mixed organic and inorganic nitrogen compounds considerably decreased the lipid content and was accompanied by a reduction in activity of the various catabolic enzymes concerned. The significance of nitrogen catabolism during lipid accumulation in this yeast is discussed.
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Cyclic GMP and Cyclic AMP Binding Proteins in Myxococcus xanthus
More LessThree binding proteins, one specific for guanosine 3′: 5′-monophosphate (cGMP) and two specific for adenosine 3′: 5′-monophosphate (CAMP) have been partially purified from vegetative cells of Myxococcus xanthus M300. The cGMP binding activity was found in the periplasmic shock fluid. Scatchard analysis indicated only a single class of binding sites with high affinity (apparent K D, 42 nm). The two cAMP binding activities were physically distinct, as indicated by their elution patterns from DEAE-cellulose, K D values and cellular locations. The cytoplasmic cAMP binding protein, which is probably identical to that previously isolated from developing myxospores of M. xanthus had an apparent K D of 57 nm, whereas the periplasmic cAMP binding protein had an apparent KD of 1 μm. During development, the nucleotide binding proteins exhibited changes in activities consistent with their postulated roles during fruiting body development.
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Adenylate Cyclase and Guanylate Cyclase in Myxococcus xanthus
More LessMyxococcus xanthus M300 vegetative cells contained significant amounts of adenylate and guanylate cyclase activity. The latter was distributed between the 100000 g supernatant and pellet fractions, required divalent cations for activity and exhibited an apparent K m of 1 mm. Adenylate cyclase activity was detected both in the l00000 g supernatant and pellet. The supernatant enzyme had an apparentK m of 220 μm with a Hill coefficient of 1·9, whereas the pellet enzyme had a K m of 72 μm and a Hill coefficient of 1·0. The isoenzymes differed in their pH optima and divalent cation requirements for optimal activity. During development of Myxococcus xanthus, the nucleotide cyclase activities exhibited changes that were substantially consistent with the roles postulated for each in a previously proposed model.
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The Detection and Analysis of Chitinase Activity from the Yeast Form of Candida albicans
More LessChitinase activity was detected in the supernatant fraction of a high-speed centrifugation preparation of broken Candida albicans yeast cells. The enzyme showed peak activity during the rapid budding phase of growth and was found to parallel the chitin synthase activity. The optimum conditions for the hydrolysis of chitin, regenerated from acetylation of chitosan, were determined. Analysis of the kinetics of the enzyme-substrate interaction and a measurement of their binding suggests that an equilibrium binding situation exists and that the kinetics follow a Langmuir isotherm interaction.
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- Development And Structure
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Shape of Nascent and Completed Poles of Bacillus subtilis
More LessThe zonal dome model has previously been shown to fit the shape of the poles of the Gram-positive Streptococcus faecium quite accurately, but measurements of the angle that the pole of Bacillus subtilis makes with the cylinder portion of the cell show that the poles of this organism do not fit this model. Furthermore, the diameters of curvatures in different parts of the completed and nascent pole are contrary to the predictions of the zonal dome model and several other proposed models. The results suggest that the poles of Gram-positive rods are generated by a mechanism designated the ‘split-and-stretch’ model. The model assumes that no additional murein is inserted as the septal wall is split and externalized.
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Glutamine Requirement for Aerial Mycelium Growth in Neurospora crassa
More LessFive amino acids are accumulated during vegetative growth of Neurospora crassa, particularly during the prestationary growth phase. Alanine, glutamine, glutamate, arginine and ornithine comprised over 80% of the total amino acid pool in the mycelium. Amino acid pools of different amino acid auxotrophs were followed during the partial transformation of a mycelial mat into an aerial mycelium. The mycelial mat under starvation and in direct contact with air rapidly formed aerial mycelium, which produced thereafter a burst of conidia. During this process, glutamine and alanine in the mycelial mat were consumed more rapidly than other amino acids; in the growing aerial mycelium, glutamate and glutamine were particularly accumulated. Of the amino acids that were initially accumulated in the mycelial mat, only a high glutamine pool was required for aerial mycelium growth induced by starvation. This requirement for glutamine could not be satisfied by a mixture of the amino compounds that are synthesized via glutamine amidotransferase reactions. It is proposed that glutamine serves as a nitrogen carrier from the mycelial mat to the growing aerial mycelium.
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Glutamine Metabolism During Aerial Mycelium Growth of Neurospora crassa
More LessDuring vegetative growth, glutamine is accumulated in the mycelium of Neurospora crassa. This high pool of glutamine seems to be required for aerial mycelium growth. Enzymes responsible for the synthesis and catabolism of glutamine were measured before and during the partial transformation of a mycelial mat into aerial mycelium. In the transforming mycelial mat, considerable activities of the biosynthetic NADP-glutamate dehydrogenase and glutamine synthetase (predominantly β polypeptide) and also some activity of glutamate synthase were observed. In the aerial mycelium, glutamine synthetase (predominantly β polypeptide) was detected, but very low activities of NADP-glutamate dehydrogenase and glutamate synthase were observed, indicating that nitrogen can be assimilated in the mycelial mat but hardly in the aerial hyphae. Accumulated glutamate in the aerial mycelium could derive from glutamine. No glutaminase activity could be detected. It is suggested that glutamate is formed through the activities of the glutamine transaminase-ω-amidase pathway and another transaminase. High activities of glutamine and alanine transaminases were observed in the aerial mycelium. These results are discussed in terms of the possible role of glutamine as a nitrogen carrier from the mycelium to the growing aerial hyphae.
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- Genetics And Molecular Biology
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The Genomes of Desulfovibrio gigas and D. vulgaris
More LessTwo-dimensional electrophoresis of sequential double-restriction digests showed that the genome of Desulfovibrio gigas comprised 1·63 × 106bp (1·09 × 109 Dal) of DNA; an ammonia-limited chemostat population possessed an average of nine genomes per cell and a multiplying batch culture possessed ∼17 genomes per cell. The genome size of D. vulgaris (Hildenborough) was 1·72 × 106 bp (1·14 × 109 Dal); a population from an ammonia-limited batch culture contained four genomes per cell. Control digestions and analyses with Escherichia coli GM4 agreed reasonably with published values: a genome size of 3·95 × 106 bp and approximately two genomes per cell from a stationary batch culture in glucose minimal medium. Desulfovibrio gigas carried two plasmids of ∼70 MDal (1·05 × 105 bp) and ∼40 MDal (6 × 104 bp); D. vulgaris (Hildenborough) contained one of ∼130 MDal (1·95 × 105 bp). Single plasmids were also detected in a second strain of D. vulgaris and in strain Berre sol of D. desulfuricans but not in 10 other desulfovibrios including representatives of D. desulfuricans, D. vulgaris, D. salexigens and D. africanus.
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Genome Size and Complexity in A◄otobacter chroococcum
All of eight strains of Azotobacter chroococcum examined contained between two and six plasmids ranging from 7 to > 200 MDal in size. Strain MCC-1, a derivative of NCIMB 8003, was cured of various of the four largest of its five plasmids and the phenotypes of the strains compared. All fixed nitrogen and exhibited uptake hydrogenase activity. No differences were observed in carbon source utilization or antibiotic, heavy metal or UV resistance. The genome sizes of two strains of A. chroococcum were determined by two-dimensional electrophoresis. Strain CW8, an isolate from local soil containing two small plasmids of 6 and 6·5 MDal contained unique DNA sequences equivalent to 1·78 × 106 (±20%) bp (1·2 × 109 Dal). In strain MCD-1, a derivative of MCC-1, containing a 190 MDal and 7 MDal plasmid, the genome size was 1·94 × 106 (±20%) bp. In exponential batch cultures, both contained 20 to 25 genome equivalents per cell. MCD-1 exhibited complex UV kill kinetics with a marked plateau of resistance; CW8 showed a simple response inconsistent with the possibility of organization of its DNA into identical chromosome copies capable of independent segregation.
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Gene Amplification in Bacillus subtilis
More LessA strain of Bacillus subtilis that carries in its genome a staphylococcal chloramphenicol acetyltransferase gene (from pC194) responds to growth at different concentrations of chloramphenicol by an alteration in the number of copies per genome of the sequences encoding the gene. Growth at 20 µg chloramphenicol ml−1 results in a 15-fold amplification of the sequences, whereas growth in the absence of chloramphenicol results in their loss. The mechanism of in situ amplification probably has much in common with that involved in R factor transitioning. The hybridization procedures that have been used for accurately determining the number of copies of the amplified DNA sequences are potentially useful for plasmid copy number determination. The findings reported here also provide a potentially useful alternative to more conventional cloning strategies that are based on autonomous plasmids in B. subtilis. The particular advantages that can be envisaged include enhanced stability of the cloned sequences and control of the number of copies that are present.
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Plasmids of the Epiphytic Bacterium Erwinia uredovora
More LessTwo Erwinia uredovora strains, 20D3 and 20D31, were analysed for the presence of plasmids. Agarose gel electrophoresis of crude lysates of these strains indicated that 20D3 carried three plasmids with molecular sizes of 88 kb, 216 kb and 260 kb while 20D31 contained five plasmids with molecular sizes of 7·8 kb, 28 kb, 105 kb, 180 kb and 260 kb. Strain 20D31 proved to be sensitive to phage GU5, suggesting that at least one of its plasmids coded for a derepressed transfer system. Curing and mobilization experiments indicated that the GU5 sensitivity was determined by the 28 kb plasmid, which was conjugative and belonged to the IncN group. Both strains lost yellow pigmentation and thiamin prototrophy when grown at elevated temperature (39 °C) or in the presence of nalidixic acid or SDS. The irreversible loss of both traits was ascribed to the curing of the 260 kb plasmid. Yellow pigmentation was due to the production of carotenoids.
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Erwinia uredovora 20D3 Contains an IncM Plasmid
More LessErwinia uredovora was lysogenized with phages Mucts62 and D108-1, a mini derivative of D108cts10 carrying a Cmr marker. The 20D3(Mucts62)(D 108-1) lysogen was induced and used as donor in a mating with a phage-resistant Escherichia coli; the Cmr marker was transferred to this recipient strain at low frequency. The analysis of the Cmr transconjugants indicated that they had acquired the pULG3 plasmid of E. uredovora associated with a D108-1 prophage. Subsequent transfer of these pULG3 derivatives within E. coli indicated that pULG3 was conjugative. Incompatibility experiments showed that pULG3 is a member of the IncM group.
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Genetic Evidence for the Direction of Transcription of the trfA Gene of Broad Host Range Plasmid RK2
More LessFor replication of broad host range plasmid RK2 in Escherichia coli two regions of the plasmid genome are essential, oriV RK2 between 12·0 and 12·7 kb on the genome (defined clockwise from the unique EcoRI site) and trfA, located between 16·0 and 17·4 kb, which provides a trans-acting product necessary for oriV RK2 function. The properties of an insertion mutant of a mini-RK2/ColEl hybrid plasmid suggest that the trfA promoter lies clockwise from the 17·4 kb RK2 coordinate. Fusion of the trfA gene lacking its normal promoter to the E. coli trpE gene in a hybrid plasmid confirmed that trfA is transcribed anticlockwise, towards the Tcr gene of RK2. Repression of trpE promoter activity in these fusions showed that replication of an RK2 replicon can be regulated by varying the level of trfA gene expression. The results also indicate the presence of a transcription unit running anticlockwise through the trfB region located between 54·0 and 56·0 kb on the RK2 genome.
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Molecular Genetic Analysis of the trfB and korB Region of Broad Host Range Plasmid RK2
More LessA 3·2 kb region of the broad host range IncP plasmid RK2 (indistinguishable from RP1, RP4, R68 and R18) anticlockwise from the EcoRI site may be separated phenotypically into three loci. The trfB/korA/korD locus both complements a temperature-sensitive maintenance mutation and suppresses the deleterious effects of the loci kilA and kilD; the incC locus expresses incompatibility towards complete RK2-like replicons, and the korB locus suppresses the host lethal effect of the kilB locus. Transcriptional fusions of the galK gene to various segments of this region revealed that all three loci are transcribed anticlockwise from a common promoter. A weak secondary promoter may also contribute to the expression of korB. Analysis of the sizes of the polypeptides produced from these segments led to the identification of two cistrons, the first encoding a polypeptide of 38 kDal associated with incC function and the second a polypeptide of 49 kDal associated with korB activity. The trfB/korA/korD activities are associated with a polypeptide of 14 kDal which may be an N-terminal fragment of the incC-associated polypeptide.
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Characterization of High-level Aminoglycoside Resistance in a Strain of Streptococcus pneumoniae
More LessThe aminoglycoside phosphotransferase (APH)(3′)(5″)-III has been characterized from Streptococcus pneumoniae BM4200, which is resistant to high levels of aminoglycosides. The phosphotransferase was apparently chromosomally-encoded and was responsible for the high-level resistance. The enzyme was not notably pH-dependent, was heterogeneous after isoelectric focusing, with pI values of approximately 4·8 and 5·1, and had an apparent molecular weight of 32500 after SDS-PAGE.
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Detection of a Membrane-associated Protein on Detached Membrane Ribosomes in Staphylococcus aureus
More LessMembrane ribosomes from Staphylococcus aureus which were detached from the membrane by extraction with the nonionic detergent Triton X-100 retained a protein (MBRP) with a molecular weight of 60000, which was absent from cytoplasmic ribosomes. MBRP was detected and quantified by immunological methods. When membrane ribosomes were dissociated into 50S and 30S subunits, MBRP remained associated with the 50S particle. MBRP was found both on membrane ribosomes and in the cytoplasm in roughly equal amounts. When added to Triton X-100-solubilized protoplasts, antibodies to MBRP produced immunoprecipitates which contained a complex of MBRP and three other proteins with molecular weights of 71000, 46000 and 41000. Four proteins with the same molecular weights as those of the MBRP complex were found associated with membrane ribosomes. The proteins of molecular weight 71000, 60000, 46000 and 41000 seemed to be present in stoichiometrically equivalent amounts in the complex.
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The Effect of Plasmid R391 and Other IncJ Plasmids on the Survival of Escherichia coli After UV Irradiation
More LessThe presence of the IncJ plasmids R391, R997, R705, R706, R748 and R749 was shown to sensitize Escherichia coli AB1157 and both its uvrA and lexA derivatives to UV irradiation. No alteration in post-irradiation survival was observed in a recA mutant containing these plasmids, compared with the non-plasmid-containing recA strain. Analysis of recombination frequency in Hfr crosses to recA +cells containing plasmid R391 indicated a reduction in recombination frequency compared with that obtained in similar crosses to a non-plasmid-containing strain. This effect was not due to plasmid-encoded restriction or entry exclusion systems and therefore must be considered as a real block in recombination. When cells containing plasmid R391 were irradiated and allowed to photoreactivate, an increase in survival was observed which was comparable to that observed in the non-plasmid-containing derivative. This indicated that postirradiation processing of UV-induced damage, or lack of such processing, by mechanisms other than photoreactivation was responsible for the UV sensitivity associated with plasmid R391.
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- Pathogenicity And Medical Microbiology
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Purificaiton by Surcrose Density Gradient Zonal Centrifugatin and Affinity Coloum Chromatogrphy of Antigenic Ssubstancaes of Antigenic Susbstances from the Livers and Mice Infected with Tyzzer’s Diseae
More LessAntigenic substances from livers of mice infected with Tyzzer's disease were purified by means of sucrose density gradient zonal centrifugation and affinity column chromatography using antiserum and checking antigenicity with the complement fixation test. Fractions obtained from zonal centrifugation fell into three main groups with different molecular weights, two of which (Fr. I and Fr. 11) positively reacted with antiserum in the complement fixation test. Both fractions were further purified by affinity column chromatography. The molecular weights of the main antigenic substances derived from Fr. I and Fr. I1 were determined to be about 52000 and 66000, respectively, by means of SDS-PAGE.
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Control Mechanisms Governing the Infectivity of Chlamydia tuachomatis for HeLa Cells: Mechanisms of Endocytosis
More LessThe mechanism by which Chlamydia trachomatis is endocytosed by host cells is unclear. Studies of the kinetics of chlamydial attachment and uptake in the susceptible HeLa229 cell line showed that chlamydial endocytosis was rapid and saturable but limited by the slow rate of chlamydial attachment. To overcome this limitation and to investigate the mechanism of endocytosis, chlamydiae were centrifuged onto the host cell surface in the cold to promote attachment. Endocytosis of the adherent chlamydiae was initiated synchronously by rapid warming to 36 °C. Electron micrographs of chlamydial uptake 5 min after onset showed that chlamydial ingestion involves movement of the host cell membrane, leading to interiorization in tight, endocytic vacuoles which were not clathrin coated. Chlamydial ingestion was not inhibited by monodansylcadaverine or amantadine, inhibitors of receptor-mediated endocytosis and chlamydiae failed to displace [3H]sucrose from micropinocytic vesicles. Chlamydial endocytosis was markedly inhibited by cytochalasin D, an inhibitor of host cell microfilament function, and by vincristine or vinblastine, inhibitors of host cell microtubules. Hyperimmune rabbit antibody prevented the ingestion of adherent chlamydiae, suggesting that endocytosis requires the circumferential binding of chlamydial and host cell surface ligands. These findings were incompatible with the suggestion that chlamydiae enter cells by taking advantage of the classic mechanism of receptor-mediated endocytosis into clathrin-coated vesicles, used by the host cell for the internalization of β-lipoprotein and other macromolecules, but were consistent with the hypothesis that chlamydiae enter cells by a microfilament-dependent zipper mechanism.
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Nonspecific Induction of β-lactamase in Enterobacter cloacae
More LessInduction of β-lactamase was monitored in a strain of Enterobacter cloacae exhibiting high resistance to most β-lactam antibiotics. Large amounts of the enzyme were induced not only in the presence of β-lactams, but also in the presence of other bicyclic molecules such as folic acid, thiamin, tryptophan or haemin. Moreover, complex media (such as Trypticase soy broth and Schaedler’s broth) and various body fluids (serum, pleural fluid and cerebrospinal fluid) also possessed considerable induction potency. Neither ‘specific’ induction (by β-lactams) nor ‘nonspecific’ induction (by other bicyclic compounds) could be augmented by addition of exogenous CAMP. These findings indicate that inducible β-lactamases deserve more attention, above all with respect to the development of resistance against third-generation cephalosporins.
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The Acid End-products of Glucose Metabolism of Oral and Other Haemophili
More LessThe acids produced in broth culture by various species of oral haemophili and by stock strains of capsulated and other haemophili were identified and measured by gas-liquid chromatography. Succinic acid was the major acid end-product of all strains, with acetic acid also being regularly produced but in smaller amounts. A stock strain, Haemophilus paraintfluenzae NCTC 4101, produced less succinic acid than other strains of this species and produced much more oxalacetic and pyruvic acid than all the other strains of haemophili. Strain NCTC 4101 possessed all the enzymes of the tricarboxylic acid cycle, as previously reported, but in the other haemophili examined only succinic dehydrogenase, fumarase and malate dehydrogenase could be detected. No other enzymes of the tricarboxylic acid cycle were detected and isocitrate lyase, malate synthase and pyruvate carboxylase were also absent. Phosphoenolpyruvate-carboxylase was present in all strains. A partial tricarboxylic acid cycle and marked malate dehydrogenase activity appear to be characteristic of haemophili. The pathway to succinate in haemophili appears to be via carboxylation of phosphoenolpyruvate to oxalacetate and thence via malate and fumarate. The results of tracer studies on a single oral strain of H.parainfluenzae using various labelled substrates were in keeping with this proposed metabolic pathway.
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Macromolecular Biosynthesis in Mycobactevium smegmatis ATCC 607 in the Presence of Antibodies to Mannophosphoinositides
More LessThe biosynthesis of DNA, proteins, RNA and phospholipids in Mycobacterium smegmatis ATCC 607 was investigated by studying the incorporation of radiolabelled components in the presence of antiserum to mannophosphoinositides. The antiserum had an inhibitory effect on the rate of synthesis of these macromolecules. However, the inhibition was greater when antibody was present together with complement.
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- Physiology And Growth
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Nutritional Diversity of Rhizobiaceae Revealed by Auxanography
More LessMany aromatic compounds are toxic when supplied at concentrations employed in most growth media. This effect was demonstrated when rhizobia and agrobacteria were grown in auxanographic plates in which cells were seeded in agar and exposed to a gentle gradient of substrate concentration. An auxanographic nutritional survey with representative strains revealed that Rhizobium japonicum and cowpea Rhizobium sp. could utilize a relatively large proportion of the aromatic and hydroaromatic compounds tested; Rhizobium leguminosarum, Rhizobium trifolii and Agrobacterium species displayed intermediate nutritional versatility; Rhizobium meliloti was relatively fastidious. The hydroaromatics quinate and shikimate were not toxic. Most of the strains examined grew at the expense of one or both of these substrates. Quinate was metabolized via protocatechuate and 3-oxoadipate. All of the strains examined were able to grow at the expense of protocatechuate and therefore must contain six structural genes for the enzymes required to convert this aromatic compound to common intermediary metabolites. Conservation of pathways for aromatic catabolism against a background of wide evolutionary divergence among the Rhizobiaceae suggests that pressures for selection of the traits were exerted throughout the evolutionary history of the organisms. A probable selective pressure is competition for nutrients in the soil. In addition, the ability of agrobacteria and rhizobia to respond to aromatic compounds may have selective value in bacterial-plant interactions.
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Survial of Legionella pneumophila in a Model Hot Water Distribution System
More LessA virulent strain of Legionella pneumophila was inoculated into an enclosed system supplied with unsterilized water from a domestic hot water supply. Growth of bacteria was monitored over 10 weeks. An increase in the number of organisms other than legionellas occurred but few amoebae were observed and none could be cultured. Viable counts of L. pneumophila in the circulation fluid decreased slightly. However, particles of debris which accumulated in the apparatus and which were stained by the indirect fluorescent antibody technique were found to be almost totally composed of L. pneumophila. On dismantling the apparatus Legionella was isolated in moderately high numbers from several different types of surfaces, particularly natural rubber and silicone.
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Dynamics of Growth Control in a Marine Yeast Subjected to Perturbation
More LessNormalized specific growth rates of cultures of the yeast Rhodotorula rubra apparently indicate the activity of a growth control mechanism, when growth is perturbed with low concentrations of a toxic inhibitor (cadmium). Data from a number of experiments, in which different cadmium concentrations were used, indicate non-linear growth control dynamics and some features of a model structure, but do not permit it to be defined. Interpretation of the oscillatory behaviour as the response of a control mechanism to perturbation suggests that inhibition of mean growth rates, indicated by a threshold on dose-response curves, is due to overloading of the control mechanism or 'saturation'. Hormesis, the tendency of subinhibitory levels of typically toxic agents to stimulate growth, is a consequence of transient or sustained overcorrections by the control mechanism to low levels of an inhibitory stimulus.
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Carbon Utilization by Free-living and Bacteroid Forms of Cowpea Rhiɀobium Strain NGR234
More LessFree-living cells of the fast-growing cowpea Rhizobium NGR234 were able to grow on a variety of carbon substrates at growth rates varying from 2·5 h on glucose or fumarate to 15·6 h on p-hydroxybenzoate. Free-living cells constitutively oxidized glucose, glutamate and aspartate but were inducible for all the other systems investigated. Bacteroids from root nodules of snake bean, however, were only capable of oxidizing C4-dicarboxylic acids and failed to oxidize any other carbon sources. Free-living cells of NGR234 possess inducible fructose and succinate uptake systems. These substrates are accumulated by active processes since accumulation is inhibited by azide, 2,4-dinitophenol and carbonyl cyanide m-chlorophenyl hydrazone. Bacteroids failed to take up fructose although they actively accumulated succinate, suggesting that the latter substrate is significant in the development of an effective symbiosis.
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Nickel Control of Hydrogen Production and Uptake in Anabaena spp. Strains CA and 1F
More LessNet aerobic H2 production and the induction of uptake hydrogenase activity in the nitrogenfixing Anabaena strains CA and 1F were strictly dependent upon the Ni2+ concentration in the growth medium. Ni2+ concentrations as low as 10 nM blocked H2 production and stimulated an uptake hydrogenase activity in whole cells. Two types of uptake hydrogenase activity were seen: a dark aerobic uptake approximately 30% as active as the H2 production rate, and a lightdependent activity in the presence of DCMU [3-(3,4-dichlorophenyl)-l, 1-dimethylurea] at low oxygen concentrations, amounting to about 50% of the H2 production rate. Together these activities may account for the strong control of net aerobic H2 production by nickel. A significant fraction of the Ni2+-stimulated uptake hydrogenase activity formed during the transition from nickel deficiency to nickel sufficiency was blocked by chloramphenicol. Nickel may be required for activation of an uptake hydrogenase, or for hydrogenase synthesis, or for synthesis of another protein which is involved in H2M uptake.
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The Effect of Oxygen on the Growth and Mannitol Fermentation of Streptococcus mutans
More LessThe effects of oxygen on growth and mannitol fermentation of eight strains of Streptococcus mutans were compared under aerobic and strictly anaerobic conditions. The growth of three strains was severely inhibited by oxygen, whereas the others were oxygen-tolerant. The growth of two of the oxygen-tolerant strains was significantly enhanced by oxygen. The activities of superoxide dismutase and NADH oxidase in extracts from aerobically grown bacteria showed a positive correlation with the growth rate under aerobic conditions. The activities of these enzymes in oxygen-sensitive strains grown aerobically were as small as those in anaerobically grown cultures. Moreover, the enzyme activities increased during aeration of anaerobically grown oxygen-tolerant strains, but not in oxygen-sensitive strains. In all strains, oxygen changed mannitol catabolism from heterolactic to homolactic fermentation. It was concluded that oxygen-tolerance of S. mutans is dependent on the ability of strains to induce NADH oxidase and superoxide dismutase.
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Nitrogen Metabolism in a New Obligate Methanotroph, Methylosinus Strain 6
More LessA new obligate methanotroph was isolated and characterized. It was classified as a ‘Methylosinus’ species and named ‘Methylosinus’ sp. strain 6. Nitrogen metabolism in ‘Methylosinus’ 6 was found to be similar to other Type I1 methanotrophs, including the assimilation of nitrogen exclusively by the glutamine synthetaselglutamate synthase system. However, unlike other Type I1 methanotrophs, it appeared that glutamine synthetase activity was regulated by adenylylation in this organism. ‘Methylosinus’ 6 was grown in continuous culture with either dinitrogen or nitrate as sole nitrogen source under various dissolved oxygen tensions. Higher rates of methane oxidation and a more developed intracytoplasmic membrane system were found at lower oxygen tensions with nitrate as the nitrogen source but at higher oxygen tensions with dinitrogen as the nitrogen source, This suggested that carbon metabolism was influenced by nitrogen metabolism in this organism.
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- Systematics
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Thymidine Kinase of Bacteria: Activity of the Enzyme in Actinomycetes and Related Organisms
More LessVarious micro-organisms were studied for their thymidine kinase (adenosine 5'-triphosphate: thymidine 5′-phosphotransferase, EC 2.7.1.21) (TK) activity. The sonicated cell extract of Escherichia coli K12 had a TK activity of 35-66 pmol thymidine monophosphate formed min-1 (mg protein)-l. The cell extracts of Salmonella typhimurium and Klebsiella pneumoniae showed a markedly higher (5- to 11-fold) TK activity. Somewhat lower but significant TK activity was detected in the cell extracts of Staphylococcus aureus, Streptococcus pyogenes, Bacillus subtilis and Proteus mzrabilis. In contrast, weak TK activity, if any, was detected in the cell extracts of Pseudomonas aeruginosa. This was also the case with respect to the cell extracts of various actinomycetes (such as Nocardia and Streptomyces) and related organisms (such as Corynebacterium, Mycobacteriurn and Rhodococcus).
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Identification of Bacillus Strains Using the API System
More LessA system is described for the rapid and accurate identification of Bacillus isolates using a matrix of results from tests in the API 20E and API 5OCHB strips and from supplementary tests. API System tests have been shown to be more reproducible than the classical tests. A taxonomy based upon API tests is in good agreement with those obtained by other methods. The results matrix can also be used in computer assisted identification.
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Volumes and issues
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Volume 170 (2024)
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Volume 169 (2023)
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Volume 168 (2022)
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Volume 167 (2021)
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Volume 166 (2020)
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Volume 165 (2019)
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Volume 164 (2018)
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Volume 163 (2017)
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Volume 162 (2016)
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Volume 161 (2015)
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Volume 160 (2014)
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Volume 159 (2013)
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Volume 158 (2012)
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Volume 157 (2011)
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Volume 156 (2010)
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Volume 155 (2009)
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Volume 154 (2008)
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Volume 153 (2007)
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Volume 152 (2006)
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Volume 151 (2005)
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Volume 150 (2004)
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Volume 149 (2003)
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Volume 148 (2002)
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Volume 147 (2001)
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Volume 146 (2000)
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Volume 145 (1999)
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Volume 144 (1998)
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Volume 143 (1997)
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Volume 142 (1996)
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Volume 141 (1995)
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Volume 140 (1994)
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Volume 139 (1993)
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Volume 138 (1992)
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Volume 137 (1991)
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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)