- Volume 131, Issue 3, 1985
Volume 131, Issue 3, 1985
- Biochemistry
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Effect of Gramicidin S on the Transcription System of the Producer Bacillus brevis Nagano
More LessThe effect of the peptide antibiotic gramicidin S, produced by Bacillus brevis Nagano, was tested on the transcription system of the producer by using in vivo, semi in vitro and in vitro systems for studies of RNA synthesis. The effects of other peptide antibiotics (linear gramicidin, tyrocidine and tyrothricin) were also tested for comparison. It was found that (a) RNA polymerase isolated from either gramicidin S-producing or non-producing strains had a similar structure and requirements and that (b) the presence of gramicidin S caused a very strong inhibition of the in vitro transcription system. We present evidence that this inhibition is most probably through formation of a complex between the antibiotic and the DNA. In vivo studies indicate that transcription during growth and sporulatio is not affected by gramicidin S and the implication is made that gramicidin S inhibits transcription during germination and outgrowth.
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Characterization in Micromonospora inyoensis of Aminoglycoside Acetyltransferase Activity Not Previously Encountered among Actinomycetes
More LessExtracts of Micromonospora inyoensis contain aminoglycoside acetyltransferase activity not previously encountered among actinomycetes. Neomycin and its derivatives (excluding butirosin) are good substrates as is the novel aminoglycoside apramycin, whereas the gentamicins and kanamycins are utilized poorly if at all. Sisomicin, which is produced by M. inyoensis, is not acetylated. When neomycin was modified by extracts of M. inyoensis the product, most probably 3-N-acetylneomycin, was inactive against cell-free protein synthesis.
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Partial Purification and Some Properties of an Aromatic-amino-acid and an Aspartate Aminotransferase in Brevibacterium linens 47
More LessAn l-aromatic-amino-acid aminotransferase (AT-IA) and an l-aspartate aminotransferase (AT-IB) were partially purified from Brevibacterium linens 47 grown on l-phenylalanine as sole nitrogen source and some properties were examined. Both enzymes were active with l-aromatic amino acids and l-aspartate. AT-IA showed 6 to 12 times higher affinity and slightly higher V max for the aromatic amino acids than for aspartate. AT-IB had higher affinity for tryptophan and tyrosine than for aspartate. However, this enzyme showed 6 to 10 times higher V max for the latter than for the aromatic amino acid substrates. Both enzymes had similar pH (8·5-9·0) and temperature (37–40 °C) optima, but they differed in their molecular weights (126000 for IA and 81000 for IB) and markedly in their thermostability. At 50 °C, AT-IB was 14 times more rapidly inactivated and its inactivation rate also increased more rapidly (z-value, 7·9 °C) as the temperature increased than AT-IA (z-value, 15·5 °C). The cofactor pyridoxal-5′-phosphate was tightly bound to both enzymes. Two enzymes co-eluted on DEAE-Trisacryl M column chromatography at pH 7·5 and could be separated by chromatography on a hydroxyapatite (HA-Ultrogel) column at the same pH. Chromatography on hydroxyapatite of AT-I from cells grown on l-phenylalanine and on ammonium sulphate revealed that AT-IA was present only in phenylalanine grown cells. AT-IB was present in both extracts at similar levels, suggesting that it is constitutive. The inducibility of IA suggested that it has an in vivo catabolic role. AT-IA is probably the key enzyme for the utilization of the aromatic amino acids as sole ritrogen sources in B. linens 47.
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Initial Oxidation and Subsequent Desulphation of Propan-2-yl Sulphate by Pseudomonas syringae Strain GG
More LessA strain of Pseudomonas syringae was isolated from garden soil for its ability to utilize propan-2-yl sulphate as sole source of carbon and energy. Growth was accompanied by disappearance of the ester from culture fluids and formation of stoicheiometric amounts of inorganic sulphate. However, enzyme activity capable of desulphating propan-2-yl sulphate was not detected under a wide range of assay conditions, either intracellular or extracellular, or at different phases of batch culture. No organic radioactive metabolites were detected during growth on propan-2-yl [35S]sulphate or [1, 3-14C]propan-2-yl sulphate alone, but when the latter compound was supplemented with unlabelled lactate, small amounts of 14C-labelled lactate were detected. This and the induction by propan-2-yl sulphate of a specific d-lactate-2-sulphatase led to a proposed pathway in which propan-2-yl sulphate undergoes a stereospecific oxidation to d-lactate-2-sulphate before rapid desulphation to d-lactate and inorganic sulphate.
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Sugar Transport and Hexose-ATP-Kinase Activity in a 2-Deoxy-d-glucose Tolerant Mutant of the Yeast Rhodotorula glutinis
More LessMutants of the obligatory aerobic yeast Rhodotorula glutinis were selected after treatment of wild-type cells with N-methyl-N′-nitro-N-nitrosoguanidine on glycerol/glutamic acid medium containing 1%2-deoxy-d-glucose. Rates of d-glucose transport in the mutants were about one-tenth that of the wild-type, whereas the transport of d-fructose and d-xylose was unaffected. However, glucose transport in the mutants was inhibited by uncouplers (for example carbonyl cyanide m-chlorophenylhydrazone) and, therefore, remained an energy-dependent process. One of the mutants, M8. was chosen for further characterization of the transport and metabolism of hexoses. Biochemical analysis of the hexose-ATP-kinase activities revealed the absence of glucokinase (EC 2.7.1.2) activity in M8. Thus, the phosphorylation capacity was reduced to one-tenth to one-fifteenth that of the wild-type, resulting in accumulation of d-glucose which, in turn, slowed down net glucose uptake. With the help of the mutant, the stoicheiometry of the H+/glucose symport in R. glutinis was determined to be one proton per molecule of d-glucose transported.
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Purification and Properties of Extracellular Glucosyltransferase Synthesizing 1,3-α-d-Glucan from Streptococcus mutans Serotype α
More LessExtracellular 1,3-α-d-glucan synthase (sucrose: 1,3-α-d-glucan 3-α-d-glucosyltransferase, EC 2.4.1. –) of Streptococcus mutans HS6 (serotype a) was purified from culture supernatant by ultrafiltration, DEAE-Sepharose chromatography and preparative isoelectric focusing. The enzyme had a molecular weight of 158000 by SDS-PAGE and an isoelectric point of pH 5·2. The specific activity of the enzyme was 48·3 i.u. (mg protein)–1. The K m for sucrose was 1·2 mm and the activity was optimal at pH 6·0. The enzyme activity was stimulated about 20-fold in the presence of dextran T10. Glucan was synthesized de novo from sucrose by the enzyme and characterized as a linear 1,3-α-d-glucan by GC–MS.
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Incorporation of Fluorotryptophan into Triostin Antibiotics by Streptomyces triostinicus
More LessThe quinoxaline chromophores of the antibiotics produced by Streptomyces triostinicus are derived from tryptophan. Protoplasts of this organism made novel products when they were incubated with dl-5-fluorotryptophan or dl-6-fluorotryptophan. When added to batch cultures of the organism. dl-5-fluorotryptophan. at concentrations as low as 10 μm, inhibited both mycelial growth and triostin production, but gave rise to novel products. These have been characterized, using fast atom bombardment mass spectrometry, as novel triostins in which one or both of the quinoxaline rings contain an atom of fluorine. The chromatographic properties of the triostins arising from the incorporation of dl-5-fluorotryptophan are very similar to those of triostins containing chlorine or bromine at position 6 of the quinoxaline ring; they are clearly different from those having a chlorine atom at position 7. Accordingly, it is suggested that the carbon atom at position 5 of the indole ring of tryptophan ends up at position 6 of the quinoxaline ring system in triostins A and C.
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Effect of Halomethanes on Aflatoxin Induction in Cultures of Aspergillus parasiticus
More LessThe addition of tribromo-, tetrabromo- and chloromethanes to cultures of Aspergillus parasiticus strongly stimulated aflatoxin biosynthesis. The presence of phenobarbital in the cultures enhanced this effect. Following the addition of 14CC14 to a culture, after 15 d incubation, 8·6% of the total radioactivity was recovered from the mycelium, and 4·7% from the culture filtrate. Some 0·4% of the total radioactivity was found in microsomes, indicating their involvement in CC14 activation and biotransformation.
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- Ecology
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The Effect of Avoparcin on Cellulolytic Bacteria of the Ovine Rumen
More LessWhen the antibiotic avoparcin was fed to sheep, changes were seen in the composition of the cellulolytic bacterial flora of the rumen. Avoparcin significantly reduced the numbers of ruminococci, but did not affect the total numbers of bacteria present, or the titre of filter paper degraders. Isolation and characterization of cellulolytic bacteria from sheep before and after avoparcin feeding began suggested that avoparcin induced a shift in the balance of the cellulolytic bacterial population from ruminococci to Bacteroides succinogenes. Comparison of the cellulolytic activity of isolates from sheep showed that B. succinogenes released label from tritiated cellulose more rapidly and extensively than did Ruminococcus albus, and that B. succinogenes was particularly active in the solubilization of highly ordered forms of cellulose, including dewaxed cotton fibres and Avicel. The pattern of establishment of antibiotic-resistant bacteria in the rumen of sheep after addition of avoparcin to the diet varied considerably one animal to another.
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Identifying Different Populations of Sulphate-reducing Bacteria within Marine Sediment Systems, Using Fatty Acid Biomarkers
More LessThe distribution of lipid fatty acids was studied in marine sediment slurries in which sulphate reduction had been stimulated by the addition of acetate, propionate, lactate or hydrogen. Acetate was directly oxidized to carbon dioxide at the expense of sulphate, propionate was incompletely oxidized to acetate at the expense of sulphate, and lactate was largely fermented (approximately 75%) to propionate and acetate, with the propionate subsequently utilized for sulphate reduction. Changes in the lipid fatty acids within these slurries were interpreted by comparison with the lipid fatty acid profiles of pure cultures of Desulfovibrio desulfuricans, Desulfobacter sp. and Desulfobulbus sp. Desulfobacter sp. seems to be the main acetate-utilizing sulphate-reducing bacterium, as in both the slurry and the original sediment the lipid fatty acids in the C12–C18 range (where bacterial contributions would be expected) were dominated by even chain fatty acids similar to the lipid fatty acid distribution of Desulfobacter sp. Desulfobulbus sp. appears to be responsible for propionate oxidation and also for hydrogen consumption as its biomarker fatty acid n-C17:1 was increased significantly by the addition of either propionate or hydrogen. Surprisingly, the biomarker for Desulfovibrio desulfuricans (br-C17:1) was not stimulated in any of the sediment slurries. The results demonstrate that there are at least two functional groups of sulphate-reducing bacteria in marine systems, and that lipid fatty acid analysis is a useful technique for investigating bacterial distributions within a complex sedimentary environment.
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Mechanisms and Kinetics of Succinate and Propionate Degradation in Anoxic Freshwater Sediments and Sewage Sludge
More LessThe interrelation of propionate and succinate metabolism in anoxic sewage sludge and in two different anoxic lake sediments was studied. The mechanism of propionate degradation and the kinetics of propionate and succinate metabolism were analysed using specifically labelled 14C tracers and gas chromatography-gas proportional counting techniques. The labels of [1-14C]propionate and [1,4-14C]succinate were transformed almost exclusively to carbon dioxide whereas the label of [3-14C]propionate was transformed to equal amounts of methane and carbon dioxide, indicating a randomizing pathway of propionate degradation. The pool sizes of propionate and succinate (0·3–2·3 μmol 1–1) were similar to each other in, but were both different between, each of the three environments studied. The turnover times of succinate were shorter than those of propionate, and the C-1 label of propionate and the C-1 and C-4 labels of succinate were metabolized far faster than the respective C-3 and C-2 and C-3 labels. These results indicate that propionate, although formed via succinate, is also degraded via succinate in the anoxic environments studied, and that succinate metabolism is at least as important as propionate metabolism in anaerobic degradation processes.
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Comparison of Ethanol Degradation Pathways in Anoxic Freshwater Environments
More LessPool sizes, turnover times and turnover rates of ethanol and acetate in anoxic sediments of Lake Mendota and Knaack Lake and in anoxic sewage digestor sludge were determined by gas chromatography-gas proportional counting techniques. Ethanol accounted for 6, 14 and 2·5% of the total carbon flux to methane in these environments, respectively. The distribution of labelled carbon in the methane and carbon dioxide fractions obtained during incubation of the anoxic materials with C-1 and C-2 labelled acetate and ethanol revealed a significantly higher degree of randomization with ethanol than with acetate tracers. HPLC analysis of sediment pore water preparations revealed that labelled acetate and propionate were formed as intermediates of labelled ethanol degradation, whereas no labelled butyrate was detected. Addition of hydrogen to Knaack Lake sediment samples inhibited ethanol degradation drastically and led to a significant accumulation of labelled butyrate. The above findings together with the results of most probable number enumerations of anaerobic ethanol-degrading bacteria indicate that propionate-forming bacteria contributed significantly to ethanol degradation in Knaack Lake sediment and in sewage sludge.
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- Immunology
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Immunochemical Studies on the Lipoteichoic Acids of Bifidobacterium bifidum subsp. pennsylvanicum
More LessAntisera to lipoteichoic acid of Bifidobacterium bifidum subsp. pennsylvanicum were obtained by injecting lipoteichoic acid/methylated BSA complexes into rabbits. Precipitin tests showed that the glycerol phosphate backbone is primarily responsible for serological specificity while the polysaccharide part of the molecule plays a minor role. Whole cells of B. bifidum subsp. pennsylvanicum were capable of absorbing antibodies, indicating the presence of lipoteichoic acid (14% of the total content) at or near the bacterial surface. Cross-reactivity with strains of the genera Bifidobacterium and Lactobacillus was tested using absorption of antiserum by whole bacteria and reactivity of phenol extracts. The results indicated that lipoteichoic acid is a common antigen within the genus Bifidobacterium. The cross-reactivity with the lactobacilli tested was very low.
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- Pathogenicity And Medical Microbiology
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Extracellular Polymer of Candida albicans: Isolation, Analysis and Role in Adhesion
More LessExtracellular polymeric material (EP) was isolated from culture supernatants of Candida albicans grown on carbon sources (50 mm-glucose, 500 mm-sucrose or 500 mm-galactose) known to promote yeast adhesion to different extents. Galactose-grown yeasts, which are the most adherent, produced more EP than sucrose-grown organisms, particularly after incubation for 5 d, while glucose-grown yeasts (the least adherent) gave the lowest yield. EP produced on all three carbon sources was of similar composition and contained carbohydrate (65 to 82%; mannose with some glucose), protein (7%), phosphorus (0·5%) and glucosamine (1·5%). Serological studies indicated that these EP preparations were immunologically identical but that galactose-grown yeasts had more antigenic determinants than sucrose-grown organisms while glucose-grown yeasts had the fewest determinants. Antigenic differences were apparent between EP preparations of some strains of C. albicans. Pretreatment of acrylic strips with EP to form a polymeric coating promoted yeast adhesion to the acrylic surface, but similar pretreatment of buccal epithelial cells with EP inhibited subsequent yeast adhesion. These results indicate that EP originates from the cell surface of C. albicans and that it contains the surface component(s), probably mannoprotein in nature, responsible for yeast adhesion.
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Killing of Yeast, Germ-tube and Mycelial Forms of Candida albicans by Murine Effectors as Measured by a Radiolabel Release Microassay
More LessCandida albicans undergoes yeast to mycelial conversion under both in vivo and in vitro conditions but the relative pathogenicity of the two forms of growth is still unknown. By adapting a recently developed 51Cr radiolabel release assay, we have quantified the killing ability of different murine effector cell populations for the hyphal form of C. albicans. Up to 50% of specific 51Cr release from the mycelial form could be detected after incubation for only 1 h, with no requirement for opsonization, provided that appropriate effector : target cell ratios were used. The specific 51Cr release correlated well with viability, as assessed by dye exclusion tests, and with pathogenicity potential in cyclophosphamide-immunodepressed mice. Comparison of the activity of different murine effectors against yeast and hyphal forms showed that hyphal forms were killed by murine effectors to a similar, if not greater, extent than yeast forms. In particular, thioglycollate-induced murine polymorphonuclear neutrophils were able to kill hyphal cells extracellularly and without an opsonic requirement.
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The Effect of Serum-factor Induced Resistance to Somatic Antibodies on the Virulence of Haemophilus influenzae Type b
More LessSUMMARY: Studies on the pathogenesis of Haemophilus influenzae b infection have used bacteria grown in vitro which are relatively serum-sensitive (using serum devoid of anticapsular antibody) compared to organisms taken from infected hosts. We compared the virulence of relatively serum-sensitive and serum-factor induced serum-resistant H. influenzae b by inoculating rats with organisms having one or the other phenotype. The serum-resistant phenotype was more virulent following intraperitoneal or intravenous inoculation; however, there was no difference in the incidence of colonization or bacteraemia following intranasal inoculation. Furthermore, organisms colonizing the pharynx of rats had the serum-resistant phenotype. Thus, different phenotypes of the same strain of H. influenzae b differed in virulence following parenteral, but not intranasal, inoculation of bacteria. This could be explained by a change from serum-sensitive to serum-resistant phenotype shortly after entering the nasopharynx. The phenotype of micro-organisms grown in vitro may differ from organisms in infected individuals and these differences may be of critical importance in studies of immunity to infection and the pathogenesis of infection.
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Association of Resistance of Neisseria gonorrhoeae to Killing by Human Phagocytes with Outer-membrane Proteins of About 20 Kilodaltons
More LessThe determinant(s) of gonococcal resistance to killing by human phagocytes has been extracted from outer membrane vesicles (OMV) of a phagocyte-resistant strain, BS4 (agar), with sodium cholate (1%, w/v). The extracts, like the OMV, nullified the effect of antiserum raised against whole BS4 (agar) to promote intracellular killing of the latter by human peripheral blood phagocytes. Fractionation of the extract on Sephadex G75 produced an active fraction with much less protein and lipopolysaccharide (LPS) than in the original extract. Furthermore, crude LPS prepared from the resistant gonococci was inactive. These results imply that the factor(s) promoting intracellular resistance is a protein. SDS-PAGE of the active fraction suggested that the factor was not a principal outer membrane protein nor one of three proteins previously thought to be associated with resistance. In contrast to a similar preparation from a phagocyte-susceptible strain, BSSH, the active fraction from BS4 (agar) showed faintly staining proteins in the regions of 20 and 60 kDal. When eluted from the gels, the former but not the latter neutralized the above effect of antisera, thus associating the 20 kDal protein(s) with resistance to intracellular killing.
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- Physiology And Growth
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A Model of the Cell Cycle and Cell Division Phasing in a Marine Diatom
More LessA model of the cell generation cycle of Thalassiosira pseudonana Hasle and Heimdal (Clone 3H) has been produced in which the cell cycle is visualized as being composed of two successive timed periods. The first period is temperature compensated but inversely proportional in duration to the rate of supply of energy (light intensity) whilst the second, culminating in division, has a high Q 10 but proceeds independently of illumination. Numerical simulations based upon this model and incorporating a feature to encompass variability in individual cell generation times have successfully generated many of the population growth features exhibited by cultures of this species grown under a variety of experimental conditions.
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Circumstantial Evidence for Phytoalexin Involvement in the Resistance of Peanuts to Aspergillus flavus
More LessThree stilbene phytoalexins, elicited by slicing and incubating imbibed peanut kernels under aerobic conditions, inhibited spore germination and hyphal extension of Aspergillus flavus with ED50 values in the range 4·9–12·8 μg ml–1. Phytoalexin yield was dependent on cultivar, conditions and duration of incubation after slicing, and crop history. The yield of phytoalexin from ten cultivars studied, after slicing and incubating at 25 °C for 24 h, ranged from 28 to 935 μg per g fresh weight and was negatively correlated with dry kernel colonization by A. flavus [r = –0·868 when plotted as In (phytoalexin concn) against In (percentage peanut colonization)]. When the incubation period was extended to 96 h there was no such correlation. Reduced phytoalexin yields were obtained when sliced kernels of one cultivar studied were incubated in water or at 37 °C, and no phytoalexin was obtained when the slices were incubated under nitrogen gas or frozen before aerobic incubation. Drought stress during pod development in four cultivars studied reduced phytoalexin yields of sliced kernels incubated at 25 °C for 24 h by 17–65% compared with non-stressed controls.
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Antigenic Population Changes of Leptospira biflexa Strains Grown Under the Selective Pressure of Factorial Antibodies
More LessSerovars jequitaia and tororò of Leptospira biflexa were cultured in the presence of homologous factor serum containing factorial antibodies (FcAbs) to their major antigens. After 39 serial passages they were then re-tested to determine whether their major antigens had remained unchanged. It was found that each parent strain had been replaced by an antigenic variant. The disappearance of each parent strain and its replacement by an antigenic variant was attributed to the selective conditions imposed by FcAbs. The antigenic variants behaved like true mutants. They lacked the major serovar antigens of the parent strains and had acquired some major antigens similar to those of two different serovars, one of which belonged to the same serogroup as the parent strain and the other to a different serogroup.
A comparison of the major antigens of the parent strains with those of their antigenic variants indicated that factorial antibodies may be used selectively to obtain antigenic variants with a predefined pattern of major antigens.
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The all2 Gene is Required for the Induction of the Purine Deamination Pathway in Schizosaccharomyces pombe
More LessFive mutants were isolated at the all2 gene on the basis of their inability to utilize hypoxanthine as a sole source of nitrogen. These mutants failed to utilize the purines adenine, hypoxanthine, xanthine, uric acid, allantoin and allantoic acid, although they could utilize urea and ammonium. The all2 mutants appeared to be defective in purine induction of uricase, allantoinase, allantoicase and ureidoglycollase activities but retained wild-type activity of the constitutively synthesized urease. The all2 mutations were recessive.
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Competence-specific Autolysis in Streptococcus sanguis
More LessStreptococcus sanguis strain Wicky activated to competence for genetic transformation is known to undergo a rapid decrease in optical density upon transfer to an alkaline buffer containing reducing agents. We studied the mechanism of this autolysis-like process and made the following observations. The process was specific because preincubation of the competence inducing factor with a specific inactivating protein prevented both cellular lysis and acquisition of competence for genetic transformation. The optical density decrease of competent bacteria involved the release of a large fraction of intracellular protein, RNA and lipid. However, no hydrolysis of phospholipid and no degradation of cell wall polymers including peptidoglycan could be detected. No peptidoglycan hydrolase activity capable of degrading radiolabeled S. sanguis cell walls was detected in unfractionated S. sanguis extracts. It is suggested that autolysis of competent S. sanguis involves the activity of a novel type of murein hydrolase that introduces only a limited number of bond breaks into the peptidoglycan.
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Characterization of DNA Fragments Encoding Fimbriae of the Uropathogenic Escherichia coli Strain KS71
More LessRecombinant plasmids were constructed that expressed the KS71A, KS71B and KS71C fimbrial antigens of the pyelonephritogenic Escherichia coli strain KS71 (04:K12) in E. coli HB101. The KS71C-encoding genes were located on a 6·4 kb HindIII–XhoI fragment obtained from the recombinant cosmid pKTH145 that expresses this antigen. Spontaneous KS71C– mutants were isolated that contained a 0·8 kb insert in a specific restriction fragment of KS71C-encoding recombinant plasmids. The KS71 B-encoding segment was located on a 11·5 kb deletable DNA fragment of recombinant cosmid pKTH144. A DNA fragment encoding the KS71A fimbria was obtained on a 12 kb EcoRI fragment of the recombinant cosmid expressing this antigen in E. coli HB101 and closely resembled the KS71B-encoding fragment. In the recombinant cosmid, the KS71 B-expressing region was flanked by homologous DNA segments. A similar stretch of DNA was found close to the KS71A-expressing DNA region.
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Isolation and Characterization of Small Heat-stable Acid-soluble DNA-binding Proteins from Bacillus subtilis Nucleoids
More LessSmall heat-stable, acid-soluble proteins (HASP) have been isolated from Bacillus subtilis nucleoids obtained from cell lysates of low ionic strength and lysozyme concentration. They were identified by their ability to bind homologous and heterologous native and denatured DNA. Four major species, of 8·5, 12, 23 and 26 kDal, were found. Their affinity for DNA was moderate as measured by the sensitivity to ionic strength of the DNA-protein complex (0·1-0·4-m-NaCl). Partial digestion by micrococcal nuclease of the ‘low ionic strength nucleoids’ released a DNA fragment of 80-120 bp. The data reported here indicate that small basic proteins, together with other components such as RNA, cations and polyamines, may be involved in the compaction of the prokaryotic genome.
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The Effect of Cerulenin on the Morphogenesis and Autolytic Activity of Bacillus subtilis
More LessPartial inhibition of lipid synthesis in Bacillus subtilis by the inclusion of cerulenin in growth media led to the formation of chains of spheroidal cells both of wild-type strains and lyt mutants. Washed cell suspensions prepared from wild-type cultures treated with cerulenin lysed only very slowly compared with those from control cultures although the activity of autolysins in 5 m-LiCl extracts made from such organisms was only about 30% less than those in extracts from controls. The behaviour of the cultures, such as the separation of cells and the reaction to β-lactams, was as if they were grossly deficient in autolytic activity. The concentration of cerulenin used (7·5 μg ml–1) reduced the growth rate two- to threefold but exponential growth at this slower rate continued for at least 18 h. The steady state concentration of total protein and peptidoglycan per unit bacterial mass was the same as in control cultures but the phospholipid content was reduced by 50%.
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Morphological Alterations of the Fission Yeast Schizosaccharomyces pombe in the Presence of Aculeacin A: Spherical Wall Formation
More LessThe fission yeast Schizosaccharomyces pombe, grown in the presence of aculeacin A (Acu), an antifungal antibiotic, forms spherical rather than cylindrical walls. This aberrant morphogenesis was studied in the presence of Acu at 1 μg ml–1 under conditions in which over 90% of the cells continued to grow but with altered morphology. Microscopic observations and chemical analyses revealed that the spherical walls had a looser structure than the cylindrical wall and that their syntheses of alkali-insoluble glucan and mannan were reduced whereas the synthesis of alkali-soluble glucan was enhanced. Spherical walls of glutaraldehyde-fixed cells were hardly digested by Zymolyase 60000 [a (1→3)-β-glucanase] but were digested by Novozym 234 [a (1→3)-α-glucanase]. From these results the components and morphology of the spherical walls are discussed in comparison with the cylindrical walls.
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Cytoplasmic Ca2+Homeostasis Maintained by a Vacuolar Ca2+Transport System in the Yeast Saccharomyces cerevisiae
More LessDifferential extraction of Ca2+ from the cytoplasmic and vacuolar pools of the yeast Saccharomyces cerevisiae, using DEAE-dextran, revealed that most of the cellular Ca2+ was bound, precipitated or sequestered within the vacuole. When the concentration of Ca2+ in the medium was raised from 10–6 m to 10–3 m, cytoplasmic Ca2+ homeostasis was maintained at 5·8 × 10–6 to 2·3 × 10–5 m, whereas the vacuoles accumulated higher concentrations of Ca2+. The results indicate that the vacuoles function as a cytoplasmic Ca2+ buffering system and as the major sequestering organelle for Ca2+. A respiratory-deficient mutant (ρ°) displayed a similar intracellular distribution of Ca2+ to the wild-type. When cells were permeabilized by DEAE-dextran the vacuoles were still capable of Ca2+ uptake. This uptake proceeded without the addition of ATP or glucose in fresh preparations but required the addition of ATP after incubation of the permeabilized cells in buffered sorbitol for 2 h. The results are consistent with the proposed Ca2+/H+ antiport in the vacuolar membrane, which is driven by formed by the H+-ATPase pumping H+ into the vacuole.
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The Effect of Pectin and Related Compounds on Encystment and Germination of Phytophthora palmivora Zoospores
More LessCitrus pectin and other uronic acids (polygalacturonate, alginate and galacturonate) accelerated encystment and germination in suspensions of Phytophthora palmivora zoospores. Other anions, polyanions and polysaccharides containing α(1→4) linkages were not effective in this respect. The uronic acids tested differed from one another both in the concentrations required for maximal rates of encystment and in the extent to which they stimulated germination as well as encystment. Pectin-accelerated encystment did not require free Ca2+in the suspending medium, but when the Ca2+concentration exceeded 100 μm, uronate-stimulated encystment and germination was suppressed. This blocking of uronate-accelerated encystment was almost specific for Ca2+, although Sr2+and Ba2+showed some effect. It is proposed that the action of uronates in accelerating encystment of P. palmivora zoospores is analogous to agonists which induce stimulus-mediated secretion in many animal cell types.
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Postponement of Cell Division by Nutritional Shift-up in Escherichia coli
More LessNutritional shifts up of synchronized or random populations of Escherichia coli (strain ML30 and derivatives of B/r and K12) to a richer medium were followed (nutritional pulse) or not (shift-up) by shifts down to the original poor medium. In most cases, the first postshift division was clearly postponed by a shift-up or a nutritional pulse. This delay of the first division was almost constant, whatever the cell age at the time of the transition, and, for the nutritional pulse only, whatever the time spent by cells in the rich medium (between 2 and 25% of the generation time characteristic of poor medium). Following a shift-up, the new steady state of division rhythm and of mean cell mass was reached at about the second postshift division, whereas after a nutritional pulse, it took three generations to return to the steady state prevailing in poor medium. When both the poor and the rich medium were varied, the extent of the postponement of cell division after a nutritional pulse increased when the amplitude of the stimulus (i.e. the difference in richness) was increased. This was not the case with a simple shift-up, where it seemed that the postponement was compensated in part by the accelerating effects of the rich medium.
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- Systematics
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The Phylogenetic Position of Streptococcus and Enterococcus
Streptococcus pyogenes, S. equinus, S. bovis, S. salivarius, S. sanguis, S. mutans, S. rattus, S. cricetus, S. lactis, S. raffinolactis and Enterococcus faecalis have been characterized by oligonucleotide cataloguing of their 16S ribosomal RNA. All the organisms form a loose but coherent group that is phylogenetically equivalent to those of lactobacilli, bacilli, the Brochothrix and Listeria group, and related taxa that constitute one of several sublines within the ‘Clostridium’ branch of Gram-positive eubacteria. Within the Streptococcus–Enterococcus group, organisms fall into three moderately related clusters defined by Enterococcus, the lactic acid streptococci and streptococci of the pyogenic and oral groups, respectively.
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- Short Communication
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Maleness in Allomyces arbuscula
More LessColoured gametangia in the male and female hybrid Allomyces arbuscula × A. macrogynus and in various mutants of A. arbuscula were essentially of two sizes, large and small, measuring approximately 1847 ± 347 μm2 and 1032 ± 179 μm2 respectively. The large coloured gametangia were the same size as those of the female wild-type. The carotene content of the culture increased with masculinization and with increases in the proportion of large coloured gametangia. Relative gametangial size alone is not a reliable phenotypic marker of sexuality in Allomyces.
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- Erratum
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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)