- Volume 131, Issue 4, 1985
Volume 131, Issue 4, 1985
- Biochemistry
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Metronidazole Inhibition of Hydrogen Production in vivo in Drug-sensitive and Resistant Strains of Trichomonas vaginalis
More LessH2 production by the human protozoan parasite Trichomonas vaginalis was monitored continuously under a mobile gas phase using a membrane-inlet mass spectrometer. Simultaneous and continuous measurement of dissolved H2, O2 and CO2 indicated that H2 evolution was inhibited at levels of O2 (<0‧25 μm) undetectable by the technique, whereas CO2 production was stimulated. Respiration was not stimulated by admitting H2 to the gas phase. Metronidazole inhibited both H2 and CO2 production. Values of K i for inhibition of H2 formation in strain ATCC 30001 (metronidazole sensitive) of 0‧16 mm and in strain 85 (metronizadole resistant) of 1‧0 mm were obtained. These data suggest that metronidazole not only competes with protons as electron acceptor but that the drug itself or a product of reduction actively inhibits some hydrogenosomal enzyme or electron carrier involved in H2 production. Under these conditions metronidazole inhibition leads to irreversible loss of cell motility.
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Composition of Lipopolysaccharide from Pseudomonas syringae pv. morsprunorum and its Digestion by Bacteriophage A7
More LessPurified LPS from a virulent cherry isolate of Pseudomonas syringae pv. morsprunorum was a mixture of smooth and rough molecular species. Mild acid hydrolysis yielded a precipitate of lipid A and a carbohydrate fraction which, by gel permeation chromatography, yielded three peaks of material. The first (high molecular weight) peak was composed almost entirely of a rhamnan, the sidechain polysaccharide. The second peak contained core oligosaccharide and comprised rhamnose, glucose, heptose, 2-keto-3-deoxyoctonate (KDO), phosphate, glucosamine, galactosamine and alanine. The third (low molecular weight) peak contained KDO, phosphate and ethanolamine. Lipid A contained glucosamine, phosphate and the fatty acids 12:0, 3-OH 10:0, 2-OH 12:0 (all ester-linked to glucosamine), and 3-OH 12:0, which was amide-linked. The typing phage A7, which uses LPS as its binding site, was found to possess a rhamnanase which split the sidechains from smooth LPS, releasing them as oligosaccharide.
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- Development And Structure
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Chemotropism of Achlya ambisexualis to Methionine and Methionyl
More LessThe chemotropic response of the water mould Achlya ambisexualis to nutrients was investigated. Among individual amino acids only methionine was active. Other amino acids were active only in combinations containing cysteine. Methionine was unique among the amino acids tested in its ability, when incorporated uniformly into the water agar substratum, to disrupt chemotropism towards an attractant mixture of amino acids. Among non-amino acid compounds tested for chemotropic activity only S-adenosylmethionine was active. Carboxyl methylation of protein was promoted by amino acid mixtures.
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Biochemical and Serological Properties of Purified Flagella and Flagellins of some Pseudomonas spp.
More LessSheared polar flagella of the type strains of monotrichate Pseudomonas aeruginosa and multitrichate P. fluorescens and P. putida were purified and the sedimentation coefficients of the corresponding flagellins determined by ultracentrifugation; from these values the approximate molecular weights of the major flagellins were calculated to be between 38000 and 43000, and other estimates based on methionine content also suggested that the range was between 38800 and 43000. Purified flagellins of these three species, and also P. syringae pv. morsprunorum and Pseudomonas sp. (‘Vibrio percolans’), were digested with trypsin, and the peptide maps obtained after two-dimensional electrophoresis were compared. Altogether 65 peptide spots were delineated and 15 peptides were found to be common to all five species. The amino acid composition of the purified flagellins of the three type species was found to accord qualitatively and quantitatively with other prokaryote flagellins. Antisera were raised against the three purified flagellins, and tested by the Ouchterlony diffusion plate method against (a) purified homologous and heterologous flagellins, (b) deflagellated cells with sheared flagella and (c) crude sheared flagella of a further 67 test strains and species (mainly Pseudomonas). With either flagella or flagellin antigens the serological reactions were virtually identical, but not all strains of a given species reacted with the relevant antiflagellin antiserum. Rapid species identification using a single antiflagellin antiserum was thus not possible. The flagellar location of the antigenic site(s) was confirmed by two serological methods, including direct immunofluorescent serology.
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- Ecology
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The Role of Different Species of Bacteria in the Hydrolysis of Protein in the Rumen
More LessProteolytic strains of Bacteroides amylophilus, Bacteroides ruminicola, Butyrivibrio fibrisolvens, Butyriribrio alactacidigens, Selenomonas ruminantium var. Ruminantium, Se. ruminantium var. lactilytica and of the genera Eubacterium, Fusobacterium and Clostridium were isolated from the rumen of sheep. The location of the proteolytic enzymens, their activity against various substrates and their sensitivity to inhibitors were compared with the same properties of mixed bacteria prepared from strained rumen fluid, in order to assess the relative importance of the different species in the hydrolysis of protein in the rumen. Bacteroides ruminicola was judged by these criteria to be the most important of these proteolytic isolates in vivo. Other isolates of higher specific activity had enzymes with properties different from rumen fluid. Species of Butyrivibrio, Selenomonas and Clostridium of lower specific activity may also be important if present in sufficiently large numbers, as their activity was of the same type as the mixed population.
Streptococcus bovis had a low proteolytic activity as determined by the conversion of 14C-labelled casein to TCA-soluble products, but was able to grow on casein, probably by virtue of its exceptionally high leucine aminopeptidase activity.
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- Genetics And Molecular Biology
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Chromosomal Map of Pseudomonas putida PPN, and a Comparison of Gene Order with the Pseudomonas aeruginosa PAO Chromosomal Map
More LessThe generalized transducing phage Pf 16h2 has been used to confirm linkage relationships of chromosomal markers of Pseudomonas putida previously determined from their time-of-entry in Hfr crosses, and to map new auxotrophic mutations. By means of spot matings using Hfr donors of known origin of transfer, catabolic markers forming part of a closely linked group of operons referred to as a superoperonic cluster have been shown to be chromosomally located and their map positions determined. R-prime-mediated interspecific complementation has been used to equate functionally 21 auxotrophic loci in P. putida and P. aeruginosa, and the distribution of these loci on the two genetic maps has been compared. While both maps reveal that auxotrophic markers are largely restricted to about 40% of the chromosome and that auxotrophic markers of similar phenotype are not clustered, there is evidence of at least seven chromosomal rearrangements since divergence from a presumed common ancestor.
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Expression of the Pseudomonas Gene Coding for Carboxypeptidase G2 in Saccharomyces cerevisiae
More LessThe Pseudomonas gene coding for carboxypeptidase G2 was introduced into Saccharomyces cereυisiae on an Escherichia coli/ yeast shuttle vector pROG5. The level of enzyme activity obtained was independent of the orientation of the gene within the pBR322-derived tetracycline resistance gene of the vector, indicating that expression can occur from a Pseudomonas promoter in yeast.
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Transport of L-Glutamine by Neurospora
More LessThe transport of the neutral amino acid l-glutamine by Neurospora crassa occurred by means of two permeases : the neutral-specific permease and the general permease. For both transport systems, accumulation of l-glutamine was a saturable process that occurred against a concentration gradient and was dependent upon metabolic energy, suggesting that accumulation is a carrier-mediated active transport process. The transported glutamine was incorporated into cellular protein. The kinetic values K m and V max were determined for glutamine transport by both systems. The glutamine analogues methionine sulphoximine and γ-glutamyl hydroxamate appear to be transported by the same permeases that transport glutamine.
In addition to determining the physiological properties of glutamine transport, we examined whether the pmn;pmb;pmg;nit-2 strain could transport this amino acid. This strain is defective for constitutive amino acid transport and for the ability to utilize amino acids as sole nitrogen sources, with the exception of glutamine. No glutamine transport was detected, suggesting that glutamine utilization by this strain is not due to its ability to transport this amino acid.
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Is Phase Variation in Bordetella Caused by Mutation and Selection?
More LessIn vitro growth conditions of Bordetella bronchiseptica led to an enrichment of phase variants. The frequency of phase variation was about 10‒6 per cell per generation. Therefore phase variation in Bordetella may result from a random mutation in a controlling region, followed by selection.
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Genetic Analysis of Fusion Recombinants and Presence of Noncomplementing Diploids in Bacillus megaterium
More LessWe have attempted to undertake genetic analysis in Bacillus megaterium using the technique of protoplast fusion that has been successfully applied in Staphylococcus and Streptomyces. Efficient production of protoplasts, fusion and regeneration techniques have been established. However, variability in numbers and types of recombinants using two-, three-, and four-factor crosses was observed throughout these studies. No linkages were detected, even between loci known to be linked by cotransduction with bacteriophage MP 13. These results were similar to those reported by Alföldi and coworkers using B. megaterium strain 216, even though the experimental design was significantly changed. During initial subculturing, segregants were observed in a 1 : 2 : 2 ratio of noncomplementing diploids : parental-l:parental-2. The ratio changed dramatically after seven subcultures. Double recombinants appeared after nine subcultures. These results corroborate those reported in B. subtilis and suggest that there is a locus-inactivation phenomenon present in Bacillus which is not evident in Streptomyces or Staphylococcus. Until the mechanism is elucidated, protoplast fusion should not be used for chromosomal mapping in B. megaterium. However, it can be used to transfer plasmids among the bacilli at a frequency of 10‒5‒10‒6 per regenerated protoplast.
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Evolution of an R Plasmid from a Cryptic Plasmid by Transposition of Two Copies of Tn1 in Providencia stuartii
More LessExamination of a series of isolates of Providencia stuartii collected over an 18 month period from a chronic-care patient at Bristol Royal Infirmary revealed the emergence of resistance to carbenicillin. Resistence was mediated by a 47 kb plasmid which transferred by conjugation to a plasmid-free strain of P. stuartii but not to Escherichia coli. Carbenicillin-sensitive isolates were either plasmid free or contained a 36 kb cryptic plasmid. Restriction endonuclease mapping of this plasmid showed it to be closely related to 32 kb and 34 kb cryptic plasmids reported previously in P. stuartii from Bristol. Mapping of the R plasmid showed it to be derived from the 34 kb cryptic plasmid by transposition of two copies of Tn1.
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Escherichia coli Thymine Auxotrophs Suppressible by Carbon Dioxide
J.W. DALE* and J.T. SMITHTwo independently-isolated thymine-requiring mutant strains of Escherichia coli were found to possess an unusual phenotype: in the presence of CO2, growth was independent of thymine. The two strains showed different profiles of temperature sensitivity. Glycine, serine and methionine were unable to relieve the thymine-dependence. Both strains were susceptible to trimethoprim under conditions where they were thymine-independent. The results are consistent with the occurrence of partial defects in thymidylate synthase.
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Inducible Plasmid-mediated Copper Resistance in Escherichia coli
More LessThe copper resistance in Escherichia coli determined by plasmid pRJ1004 is inducible. The level of resistance is proportional to the inducing dose of copper. The level of copper resistance in induced and uninduced cells changes with the growth phase of the culture. Induced resistant cells accumulate less copper than uninduced cells, so that reduced accumulation may be the mechanism of resistance. We propose that the inducible plasmid-coded copper resistance interacts with the normal metabolism of the cell to protect against toxic levels of copper while allowing continued operation of copper-dependent functions.
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Interactions between Mutations Affecting Ribosome Synthesis in Escherichia coli
More LessRNA synthesis was followed during amino acid starvation of strains of Escherichia coli that contained both the relaxed (relA) mutation and a mutation affecting ribosome assembly that results in oversynthesis of RNA. The ribosome mutation did not by itself lead to relaxedness. The relaxed mutation could be expressed in organisms that contained the ribosome mutation.
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Three Restriction Endonucleases from Anabaena flos-aquae
More LessThree site-specific endonucleases, AflI, AflII and AflIII, have been partially purified from the cyanobacterium Anabaena flos-aquae CCAP 1403/13f. Their recognition and cleavage specificities have been determined to be:
AflII and AflIII are new specificities and may be useful in molecular cloning, as well as in the analysis of DNA. The distribution of type II restriction endonucleases in the cyanobacteria is briefly discussed.
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Effects of Transition Mutations in the Regulatory Locus spoIIA on the Incidence of Sporulation in Bacillus subtilis
More LessWe have determined the changes in DNA sequence corresponding to three mutations in the promoter-proximal open reading frame of spoIIA, a locus that regulates sporulation in Bacillus subtilis. All three mutations prevent the synthesis of two sporulation-associated enzymes, but they differ in their effects on spore incidence. We now find that mutation spo-42, which allows spores to be produced at a low incidence, is a transition that changes Gly95 to Asp in the protein encoded by the open reading frame. Mutation spo-69, which blocks sporulation entirely, consists of two transitions: these change Gly62 to Asp and Ala116 to Thr. Mutation sas-1, which partially suppresses spo-69, is also a transition : this changes residue 62 (which had become Asp as a result of the spo-69 mutation) to Asn.
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- Pathogenicity And Medical Microbiology
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Adhesion, Penetration and Intracellular Replication of Legionella pneumophila: an in vitro Model of Pathogenesis
More LessLegionella pneumophila attached to, penetrated and replicated within the three eukaryotic cell lines, MRC-5, HEp-2 and Vero. Multiplication occurred rapidly in these cells for an initial 48 h after inoculation and declined thereafter. Infected MRC-5 cell monolayers developed lytic-type cytopathic changes, with organisms being readily released. HEp-2 cells showed a more chronic infection, with slowly developing granular changes in the monolayers, and slow release of intracellular bacteria. In Vero cells, organisms were released rapidly along with a more progressively developing granular cytopathic effect in the monolayers. L. pneumophila was unable to grow in cell-free culture fluids. Uptake and intracellular development was similar for each cell type, and was initiated by ‘bacteriopexis’, a process in which the organisms bound via receptors and were surrounded by cellular microvilli which eventually fused, leading to bacterial engulfment. Replication of organisms in vacuoles within the cytoplasm of infected cells was confirmed by thorium labelling. These vacuoles were lined with ribosomes and, at the early stages of intracellular development, were found in close proximity to mitochondria, cytoplasmic filaments and banded enclosures. Ruthenium red staining showed that acid mucopolysaccharide capsular material was not present on these organisms during the attachment process or intracellular phase. Organism release was by lysis of the infected cells.
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Purification and Characterization of a Corynebacterium ulcerans Bacteriocin (Ulceracin 378)
More LessCorynebacterium ulcerans strain 378 produces a bacteriocin (ulceracin 378) and a toxin when grown on semi-solid medium. Ulceracin 378 was purified 360-fold by dialysis and chromatography on DEAE-cellulose and Sephadex G-200. On the basis of Ultrogel AcA22 gel filtration its molecular weight was about 900000. It could be dissociated by 2-mercaptoethanol and sodium dodecyl sulphate into smaller subunits of 25000. The bactericidal activity was associated with this subunit which contained no carbohydrate or lipid. Ulceracin 378 was thermostable and stable over a wide pH range. Purified ulceracin 378 did not have a toxic effect (lethal) on guinea-pigs and rabbits and was immunologically distinct from the toxin.
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Reaction Components Influencing CAMP Factor Induced Lysis
More LessThe reaction components and conditions affecting CAMP factor (Streptococcus agalactiae) induced lysis of target cells have been investigated. Both the amount of sphingomyelinase used and the time of preincubation with sphingomyelinase directly affected the rate of haemolysis by CAMP factor. The CAMP factor induced lysis was temperature dependent between 15 and 30 °C and was proportional to the amount of CAMP factor added.
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- Physiology And Growth
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Production of Methanethiol from Methionine by Brevibacterium linens CNRZ 918
More LessThe conditions under which Brevibacterium linens CNRZ 918, a strain isolated from the surface smear flora of Gruyère de Comté cheese, produced methanethiol from methionine were studied. Demethiolation was estimated from the methanethiol production capacity of resting cells. Methionine was demethiolated mainly during the exponential growth phase of the organism during which time the cells were rod-shaped and had a generation time of 5 h, and the medium became alkaline. At the end of growth (pH 9) the cells were coccoid, and produced only very little methanethiol. The production of methanethiol required the presence of methionine in the culture medium, this reflecting the probable induction of the enzyme systems involved. Glucose favoured growth and inhibited production of methanethiol. Lactate favoured both growth and methanethiol production.
Resting rod cells also produced methanethiol from structural analogues of methionine and from methionine-containing peptides. The apparent kinetic constants of the production of methanethiol for rod and coccoid cells were respectively K m = 14 mm and 46 mm, V max = 208 nkat g–1 and 25 nkat g–1. The optimum temperature and pH for production were 30 °C and pH 8. Azide or malonate favoured the production of methanethiol by resting cells, whereas chloramphenicol had no effect.
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Variations in the Volumes of Microbial Cells with Change in the Agitation Rates of Chemostat Cultures
More LessDuring continuous cultivation of Bacillus cereus, Staphylococcus epidermidis, Saccharomyces cerevisiae and two different strains of Escherichia coli, mean cell volume was found to be directly proportional to the agitation rate of the fermenter. For any one piece of equipment and microbial strain, highly reproducible linear relationships were measured, with similar intercepts and gradients for aerobic and anaerobic cultures independent of overall medium concentration, gradients for nitrogen-limited culture being always greater than those for carbon-limited culture. Alternative fermenter configurations or use of a different microbial strain furnished similar linear relationships, but slope and intercept were changed, indicating a dependence both on the geometry of the fermentation system and also on the microbial strain.
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Selection for Nonadherent or Nonhydrophobic Mutants Co-selects for Nonspreading Mutants of Cytophaga johnsonae and Other Gliding Bacteria
More LessPredictions based on a general model of surface components involved in gliding motility of Cytophaga johnsonae along with characteristics of previously isolated nonspreading mutants of C. johnsonae led us to suspect that isolation of such mutants could be accomplished by selecting for nonadherent or nonhydrophobic mutants. Accordingly, conditions were devised to select for mutants that failed to attach to cheesecloth suspended in growth media and for mutants that failed to adhere to n-hexadecane droplets. Populations of cells obtained from both selection procedures were screened for mutants producing nonspreading colonies. Both techniques resulted in enrichment for nonspreading mutants that were classified by previously established criteria as MNS (motile nonspreading), CNS (conditional nonspreading) or TNM (truly nonmotile). When assayed for adherence and hydrophobicity, all TNM mutants were nonadherent and nonhydrophobic, compared with wild-type cells. Most mutants of the other two classes were unchanged with respect to these properties. Results from subjecting cells of four other strains of gliding bacteria to selection by the same procedures indicate that the methods will be broadly applicable for isolating nonspreading mutants of gliding bacteria.
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The Ammonium Permease of Rhizobium leguminosarum MNF3841
More LessAn ammonium permease was derepressed when Rhizobium leguminosarum was grown in chemostat culture under conditions of nitrogen limitation. The ammonium permease was characterized by direct measurements with an ion-specific ammonium electrode. Cells grown under ammonia, nitrate, glutamate or methylamine limitation had permease activity, while those grown with excess (10 mm) ammonium chloride or glutamate did not. On transfer from N-limited to N-excess conditions, the permease disappeared rapidly, and all activity was lost within 18 h. Uptake by the permease was sensitive to azide, carbonyl cyanide m-chlorophenylhydrazone,2,4-dinitrophenol, nigericin and valinomycin. The apparent K m for was 0·015 mm; ammonium uptake had a narrow maximum around pH 7·5. The internal ammonia concentration of N-limited cells was 0·4 mm, with up to 60-fold gradients of was 0·015 mm; forming across the membrane within 30 min. Hydrazine and hydroxylamine strongly inhibited ammonium uptake, with methylamine, glutamine, aspartate and glycine less effective as inhibitors. Isolated pea bacteroids capable of transporting succinate did not possess the ammonium permease.
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Uptake of Succinate and Malate in Cultured Cells and Bacteroids of TWO Slow-growing Species of Rhizobium
More LessThe uptake of succinate and malate has been compared in cultured cells and bacteroids of two species of slow-growing Rhizobium: R. japonicum (USDA I-110) and cowpea Rhizobium (USDA 3278). Cultured cells of both organisms actively accumulated both compounds, and uptake was abolished by KCN and 2,4-DNP, but not by arsenate. Kinetic studies using cultured cells showed that succinate competitively inhibited malate uptake, and vice versa, implying a common step in the uptake of these dicarboxylic acids. Uptake of both of these compounds was inhibited by osmotic shock and N-ethylmaleimide in cultured cells of both species. Purified bacteroids accumulated succinate in a process that was sensitive to 2,4-DNP and KCN, but at a rate significantly slower than for cultured cells. No detectable malate uptake was observed in purified symbiotic cells. Furthermore, succinate uptake was insensitive to osmotic shock in bacteroids of both strains. These results show that although bacteroids of both strains are competent in succinate uptake, significant differences exist in the expression and/or stability of dicarboxylate uptake systems between free-living and symbiotic cells.
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Mechanism of Action of Nikkomycin and the Peptide Transport System of Candida albicans
More LessNikkomycin was found to be a potent growth inhibitor of Candida albicans through competitive inhibition of chitin synthase [K i = 0·16 μm (0·1 μg ml–l)]. The activity of the peptide-nucleoside drug was antagonized by both peptone and defined peptides. Transported dipeptides were effective antagonists while transported oligopeptides were not. A mutant of C. albicans resistant to the effects of nikkomycin through a transport defect was unable to transport dipeptides, while oligopeptide uptake was apparently unaffected. At least two peptide permeases are operational in this organism.
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Phospholipid Biosynthesis in the Moderately Halophilic Bacterium Vibvio costicola During Adaptation to Changing Salt Concentrations
N.J. RUSSELL, M. KOGUT and M. KATESThe metabolism of phospholipids in Vibrio costicola, a moderately halophilic bacterium, has been investigated in relation to sudden changes in salinity. Both the absolute and relative rates of biosynthesis of phosphatidylglycerol and phosphatidylethanolamine depend on the salt concentration of the medium; a sudden rise in salt concentration has an instantaneous inhibitory effect on phospholipid biosynthesis, but this inhibition lessens as. the bacteria adapt to the higher salinity. There is no turnover of phospholipids during isotonic growth, nor when the salt concentration is suddenly altered. The alterations in biosynthetic rates of phosphatidylglycerol and phosphatidylethanolamine that occur after sudden changes in salt concentration are consistent with the known compositional changes. We conclude that the mechanisms of changes in phospholipid composition during adaptation to raised or lowered salt concentrations are not necessarily the same.
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Dissimilatory Sulphur Metabolism in Phototrophic ‘Non–sulphur’ Bacteria
More LessFour species of the purple ‘non-sulphur’ bacteria (Rhodospirillaceae) were examined with respect to their dissimilatory sulphur metabolism. Under anaerobic conditions with CO2 as sole carbon source, cell suspensions of Rhodopseudomonas sulfoυiridis, Rhodobacter υeldkampii and Rhodo-bacter adriaticus, all dependent on reduced sulphur compounds for growth, oxidized sulphide to an intermediate compound (elemental sulphur, possibly polysulphides) that was converted either partly (R. υeldkampii) or completely into sulphate, whereas thiosulphate oxidation occurred without detectable intermediates. In contrast, Rhodobacter sulfidophilus oxidized sulphide as well as thiosulphate to sulphate. Both oxidations occurred with simultaneous excretion of sulphate and sulphite; the latter was subsequently also transformed into sulphate. In cell-free extracts the presence of a reverse sulphite reductase could not be proven. An adenosine 5′-phosphosulphate (APS) reductase could not be detected either, but all strains contained a membrane-bound sulphite oxidoreductase that is obviously responsible for sulphate production. This enzyme was solubilized and partly purified from R. adriaticus, Rps. sulfoυiridis and R. sulfidophilus.
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Buoyancy Regulation in a Strain of Microcystis
More LessA strain of the gas-vacuolate cyanobacterium Microcystis was found to float in cultures grown at low light intensities and to sink in those grown at high intensities. The loss of buoyancy that occurred within 1 to 5 h on increasing the photon flux density from 10 to l00 μmol m–2 s–1 was investigated by centrifuging the cell suspensions in a horizontally placed capillary with a rectangular cross-section, and then separately counting the floating cells under the upper tube surface and sinking cells on the lower surface. Buoyancy loss was not accompanied by loss of gas vesicles, as occurs in some other planktonic cyanobacteria, but was caused by a relative increase in dry matter, principally carbohydrate, without a corresponding increase in gas vesicles. The increase in light intensity gave an increase in cell turgor pressure but this was insufficient to collapse the strong gas vesicles present in this strain, which had a median critical pressure of 0·75 MPa (7·5 bar).
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Recurrent Senescence in Axenic Cultures of Physarum polycephalum
More LessWhen subcultures of the aux-2 and aux-4 strains of Physarum polycephalum, which had been grown for more than four years in axenic shake culture, were transferred to non-axenic surface culture they displayed progressively shorter lifespans (older axenic surface cultures yield shorter lived non-axenic cultures). Similar subcultures transferred to axenic agar medium also underwent senescent-like events. These subcultures, after a period of vigorous growth, displayed a slower growth rate, reduced cytoplasmic streaming, loss of yellow pigment, and eventually they fragmented into a number of small spherical structures with the concomitant lysis of most of the plasmodium. In non-axenic culture these structures quickly degenerated (and disappeared from the culture); however, in axenic culture they revived and after several days produced new vigorous plasmodia. Following a period of vigorous growth the plasmodium again underwent senescent-like events. This cycle of senescence and growth was repeated a number of times before death finally occurred.
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Properties of the Germination Inhibitor of Streptomyces viridochromogenes Spores
More LessGerminating spores of Streptomyces viridochromogenes excreted a substance into the surrounding medium which inhibited germination of another sample of the spores. The germination inhibitor (GI) was produced during submerged culture after exponential growth had ceased. The GI was purified 51-fold following extraction from growth liquor with chloroform. It was soluble in alcohol and water and had a molecular weight of less than 1000. The GI blocked growth and respiration of some Gram-positive bacteria and was an inhibitor of the membrane bound, but not solubilized, calcium-dependent ATPase of germinated spores and mycelia of the producing organism. Several sodium–potassium activated ATPases were also inhibited. All four activities (respiration, growth, germination inhibition. ATPase) co-purified during column and thin-layer chromatography. The GI activities released during germination and produced during growth were identical. A role for the GI antibiotic in regulation of dormancy of spores of the producing organism is discussed.
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Effect of Oxygen Concentration on the Growth and Respiratory Efficiency of Acinetobacter calcoaceticus
More LessMaximum molar growth yields on oxygen ( ) and succinate ( ) were not affected when carbon-limited Acinetobacter calcoaceticus NCIB 8250 was changed to oxygen limitation.→H+/O quotients for cells grown with succinate- or ammonium-limitation did not differ significantly from those obtained with oxygen-limited cells. The levels of cytochromes b and o remained constant at 0‧13 and 0‧05 nmol (mg protein)–1 respectively in crude cell-free extracts of succinate-limited organisms grown at high (80 mmHg) or low (5–10 mmHg) dissolved oxygen tension respectively. Their levels increased in oxygen-limited conditions, when cytochrome a 2(d) was additionally synthesized and organisms exhibited increased resistance to cyanide inhibition of respiration. It is concluded that the respiratory efficiency of A. calcoaceticus NCIB 8250 is unaffected by oxygen concentration under the conditions studied. Theoretical calculations are presented for maximum molar growth yields on succinate and oxygen and these are compared with experimental values. Although the effective P/O ratio is only about unity, energy is probably conserved at two sites of oxidative phosphorylation and this is independent of the de novo synthesis of cytochrome a 2 (d) under conditions of oxygen limitation. Possible reasons for the observed low molar growth yields are discussed.
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Growth Yields and Respiratory Efficiency of Acinetobacter calcoaceticus
More LessAcinetobacter calcoaceticus NCIB 8250 was grown in batch culture on 46 separate sources of carbon + energy and the molar growth yields were measured. The organism was also grown in continuous culture on l-mandelate, phenylglyoxylate and succinate and the results used to calculate maximum molar growth yields. The elemental composition of the bacteria was determined. Growth equations for each substrate were constructed so that the amount of oxygen consumed per mol of substrate could be calculated. Growth yields on oxygen (Y O2 ) were then estimated. The Y O2 values were low [averaging about 19 g dry wt (mol O2)–1]. The most likely explanation for the low yields is that the effective P/O ratio is only about one, although there are probably at least two sites of oxidative phosphorylation.
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- Short Communications
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Detection of Chlamydia truehornatis in Clinical Specimens by Nucleic Acid Spot Hybridization
More LessA nucleic acid spot hybridization assay was used to detect Chlamydia trachomatis DNA. The hybridization probes included DNA isolated from elementary bodies of lymphogranuloma venereum (LGV) strains and cloned fragments of both chromosomal and plasmid DNA.The sensitivity of the test was in the range 10 to 100 pg homologous DNA and 10 in υitro infected cells. Cross-reactivity with bacterial DNA was avoided when purified chlamydia-specific DNA fragments were used as probes. C. trachomatis was detectable in most of the clinical specimens with large amounts of infectious particles. Also some isolation-negative specimens gave a positive signal in the test.
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The Loss of a Large DNA Fragment is Associated with an Aerial Mycelium Negative (Amy–) Phenotype of Streptomyces cattleya
Hybridization of various Streptomyces cattleya aerial mycelium negative (Amy–) mutants with a probe containing the gene for argininosuccinate synthetase (pTG17) has revealed the presence of two different types of mutants (stable and unstable). Stable mutants appear to have lost all or part of the region covered by the probe, while the unstable mutants demonstrate no detectable changes in this region. In one group of stable mutants (those demonstrating a partial loss of sequences hybridizing to the probe), a 4·17 kb extrachromosomal element was detected, which hybridized with the pTG 17 probe. The significance of this finding is discussed with reference to the genetic instability of the genus Streptomyces.
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Volumes and issues
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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)