- Volume 129, Issue 1, 1983
Volume 129, Issue 1, 1983
- Biochemistry
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Occurrence and Some Properties of Two Threonine Dehydratases in Euglena gracilis
More LessTwo threonine dehydratases, I and II, were found to occur in Euglena gracilis and each enzyme was purified partially. Like the biosynthetic threonine dehydratases of other organisms, dehydratase I was feedback-inhibited by isoleucine and not affected by adenylates. Dehydratase II was not influenced by branched-chain amino acids and adenylates. Occurrence of dehydratase II, with a much higher activity than dehydratase I, suggests that dehydration of threonine is not the key point in the regulation of isoleucine biosynthesis in E. gracilis.
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Biosynthesis of the Envelope Glycolipids during Heterocyst Development in Anabaena cylindrica
More LessIncorporation of sodium [1-14C]acetate into the heterocyst-specific glycolipids and glycerolipids of the cyanobacterium Anabaena cylindrica during induced heterocyst differentiation indicated that (1) the activity of key enzymes involved specifically in the biosynthesis of the very long chain polyhydroxyalkanes and hydroxyfatty acid moieties of the heterocyst glycolipid fraction is stimulated during heterocyst differentiation, and (2) in mature heterocysts, formation of the characteristic very long chain heterocyst glycolipids essentially ceases.
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Detection of a Proteinase Inhibitor in Aspergillus nidulans
More LessThe activity of proteinases in mycelial extracts of Aspergillus nidulans increased during storage. The rate of activation increased with temperature. Three separate proteinase activities, differing in their electrophoretic mobilities on polyacrylamide gels, were readily detected at pH 6.5. Inhibitory activity, effective against all three proteinase activities, was also detected in fractions prepared from fresh mycelial extracts. The inhibitory factor(s) were heat-stable and non-dialysable. The inhibitory activity was lost during storage of mycelial extracts. It is proposed that the inhibitory factor(s) are digested by the proteinases during storage.
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- Development And Structure
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Inhibitors of Fruiting-body Formation and Challenge Time Experiments in Myxococcus xanthus
More LessPurines, amino acids and their analogues, polypeptide and other antibiotics, and a range of other chemicals were screened by a spot-testing technique for inhibition of vegetative growth, or of fruiting-body formation, in the bacterium Myxococcus xanthus. Selected fruiting inhibitors were tested by challenge time-transfer experiments. In general, delayed addition of inhibitors up to the time of late aggregation prevented subsequent completion of fruiting. Conversely, cells held in the presence of a fruiting inhibitor for extended periods did not rapidly lose the ability to fruit subsequently on removal of the inhibitor.
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Surface Structure of Bacteroides nodosus in Relation to Virulence and Immunoprotection in Sheep
More LessA comparative electron microscopic study was made of virulent ovine strains, benign ovine strains, bovine strains and culture variants of Bacteroides nodosus using negative staining, thin section and freeze-fracture etch techniques. The plasma membrane, peptidoglycan layer and outer membrane structures were similar in all the organisms, but there were marked differences in the presence of pili, diffuse polar material and additional layer. The variations in these surface structures were examined in relation to the virulence and immunoprotection of B. nodosus towards foot-rot in sheep. Only organisms with abundant pili caused virulent foot-rot; diffuse polar material and perhaps the additional layer may also be associated with virulence, but conclusive evidence was lacking. It appeared that pili and one or more unknown cell components, possibly diffuse polar material but not the additional layer, were necessary for immunoprotection.
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Effect of Papulacandin B on the Cell Wall and Growth of Geotrichum lacti
More LessAddition of the antifungal antibiotic papulacandin B to an exponential culture of Geotrichum lactis inhibited incorporation of glucose into the alkali-insoluble and alkali-soluble glucan fractions of the hyphal wall, although the rate of growth was practically unaltered. Synthesis of other cell wall components (i.e. galactomannan and chitin) was not affected. Papulacandin B also induced the proliferation of branches along the hyphae which continued to branch dichotomously resulting in a ‘colonial’ pattern of growth. Aculeacin A, another antifungal antibiotic that inhibited β-glucan synthesis also caused morphological alterations similar to those described for papulacandin B. Inhibition of β-glucan synthesis and the altered growth pattern persisted for several hours after removal of the antibiotic. Recovery of β-glucan synthesis and restoration of the normal pattern of growth occurred simultaneously. Growth of G. lactis in l-sorbose medium also led to inhibition of β-glucan synthesis and dichotomous branching.
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- Ecology
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Stimulation of Methanogenesis by Slurries of Saltmarsh Sediment after the Addition of Molybdate to Inhibit Sulphate-reducing Bacteria
More LessThe addition of 20 mm-molybdate to sediment slurry in order to inhibit sulphate-reducing bacteria increased the amount of methane formed. Only a small proportion (7.8%) of the total methane came from the H2 + CO2 pathway, while methanogenesis from acetate was negligible. Conversion of-14C-labelled formaldehyde, methanol and methionine to 14CH4 by sediment slurry in the presence of molybdate showed that these were potential precursors of the additional methane, although lack of adequate analytical techniques precluded establishment of the quantitative significance of this turnover; [14C]formate was not converted to 14CH4. It is suggested that inhibition of sulphate-reducing bacteria by molybdate immediately increased methanogenesis from formaldehyde, methanol and methionine, and to some extent from H2 + CO2. There was also evidence for longer term development of an increased methanogenic bacterial population when there was no competition from the sulphate-reducing bacteria for available nutrients.
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Bacterial Reduction of Ferric Iron in a Stratified Eutrophic Lake
More LessThe rate of release of Fe(II) from anoxic lake sediments was lower in the presence than in the absence of nitrate. The reduction of Fe(III) by the sediments had a temperature optimum of 30 C and was inhibited by HgCl2, suggesting that the process was largely biological in nature. Of the iron sources tested with cultures of anaerobic iron-reducing bacteria, FeCl3 was the most readily reduced and goethite the least. Reduction was faster in the presence of a chelating agent and was suppressed by the addition of NO- 3, ClO- 3, MnO2, Mn2O3 and O2. An iron-reducing chemoorganotroph, tentatively identified as a member of the genus Vibrio, was isolated. Physical contact between the bacterium and iron particles was essential to ensure maximum rates of Fe(III) reduction but > 30% of the activity appeared to be associated with extracellular components. Although Fe(III) reduction by whole cells and cell-free extracts was decreased in the presence of electron transport inhibitors, the molar growth yield of the organism was unaffected by the presence of Fe(III). It is assumed that the organism used the Fe(III) as a hydrogen sink. A second organism, an anaerobic facultative chemolithotroph, appeared to conserve energy by the reduction of Fe(III). Biomass yield (measured as ATP) was greater in the presence of Fe(III), and the organism was able to use H2 as a source of reducing power.
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Methanogenic Degradation of Sodium Benzoate in Profundal Sediments from a Small Eutrophic Lake
More LessEnrichments were established to examine the potential of Blelham Tarn profundal sediment to metabolize benzoate to CH4 and CO2. Longadaptation times were required before benzoate-dependent CH4 production occurred, though both increased inoculum size and prior methanogenic adaption to aliphatic fatty acids reduced the adaptation time. Benzoate was metabolized according to the stoichiometry: 4C6H5COOH + 18H2O 15CH4 + 13CO2. The optimum temperature for CH4 production from benzoate in the enrichments was 37°C irrespective of the enrichment temperature. Methanogenic benzoate degradation was associated with a particulatefloc in the enrichments and Methanobacterium soehngenii was tentatively identified as an important constituent of this floc by scanning electron microscopy. Anaerobic benzoate fermentation was observed after 4 h in undiluted sediment by the use of [14C]benzoate, and the temperature optimum for 14C-labelled gas formation was 28°C. The 14CH4: 14CO2 ratio indicated that methanogenic fermentation of benzoate was occurring in situ. CO2 became the main gaseous product from [14C]benzoate when sulphate was added to sediment, and 20 mm-molybdate reversed this effect. Methanogenesis was slightly inhibited by addition of 20 mm-molybdate. Methanogenic benzoate fermentation in sediments was found to be inhibited by H2.
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DNA Colony Hybridization to Identify Rhizobium Strains
More LessDNA colony hybridization was found to have a high generic and strain specificity for Rhizobium trifolii. We have assessed the use of this technique to determine occupancy of nodules by strains of Rhizobium and found that its high degree of specificity allowed successful identification of rhizobia from nodules. Other techniques currently available for determining the Rhizobium strain involved in forminsg a particular nodule lack specificity or interfere with symbiotic capabilities of the rhizobia.
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Ecological Factors Determining Establishment of Cellulolytic Bacteria and Protozoa in the Rumens of Meroxenic Lambs
More LessEcological factors that control the establishment of cellulolytic bacteria and ciliate protozoa in the lamb rumen were studied in meroxenic animals. Axenic lambs received dilutions of rumen liquor from either conventional lambs and sheep (pool A) or meroxenic lambs (pool B).
The total number of bacteria established in the rumen was between 109 and 5 × 1010 g−1. In lambs inoculated with dilutions (10−6, 10−7, 10−8) of pool A, cellulolytic bacteria did not become established. However, subsequent inoculation with Bacteroides succinogenes, resulted in colonization in lambs that had received 10−6 and 10−7 dilutions of pool A. However, B. succinogenes became established in only one of three lambs that received the 10−8 dilution. Similar results were obtained for the protozoan Entodinium sp.
With pool B, lambs were inoculated earlier and cellulolytic bacteria were established directly from the 10−6 and 10−7 inocula. Polyplastron multivesiculatum establishment occurred readily when inoculated into the lambs which had received the 10−6 dilution of pool B.
Results obtained in this study suggest that establishment of cellulolytic bacteria and protozoa requires an abundant and complex flora and is favoured by early animal inoculation.
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- Genetics And Molecular Biology
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Photosensitivity in Thiopyronine-resistant Yeast Mutants
More LessIn yeast, thiopyronine (TP) acts both as a growth inhibitor (in the dark) and a photodynamic sensitizer (in the light). We have isolated a large number of TP-resistant mutants of Saccharomyces cerevisiae and characterized them by genetic and photobiological techniques. Resistance to the growth-inhibitory (dark) effects of TP can arise by mutations in at least four separate genes. Growth-inhibitory and photodynamic effects of TP can be genetically separated, as evidenced by the finding that resistance mutants affected in three of the genes were not altered in their photodynamic response to the dye. In contrast, a mutation in the fourth gene simultaneously conferred high resistance to both the growth-inhibitory and photosensitizing effects of TP, suggesting that a mutation had occurred at a step common to the expression of both effects. Preliminary data suggest that this mutation reduces the ability of the cells either to take up, or bind, TP.
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Polymorphism in Escherichia coli: rtl atl and gat Regions Behave as Chromosomal Alternatives
More LessAmongst forty wild strains of Escherichia coli, sixteen utilized galactitol (as did K12) and seven utilized ribitol (as did C) of which six utilized d-arabitol; none utilized all three polyols.
Transduction of genes for ribitol utilization (rtl +) to strains able to utilize galactitol (gat +), whether K12 or wild strains, using wild strains and E. coli C as donors always resulted in loss of the galactitol phenotype. The genes for d-arabitol use (atl +) were always cotransduced with rtl + in interstrain crosses. We confirm and extend the mapping of gat + ( Lengeler, 1977 ) and rtl + atl + ( Reiner, 1975 ) in their respective hosts, K12 and C, by showing both regions to be 50% cotransducible with metG and 3% cotransducible with fpk. In reciprocal transductions, gat + replaced rtl + atl +. In partial diploids, rtl + atl + and gat + regions did not interfere with each other’s expression.
Transfer of rtl + from an Rtl+ Atl− donor by R plasmid (pE10)-mediated conjugation, gave Gat− transconjugants of K12 in which rtl + and a kanamycin resistance gene were 100% cotransducible in the metG region of the chromosome.
It is suggested that the rtl + atl + and gat + genes (or parts of them) act as alternative, or mutually exclusive, regions in the chromosome. Possible reasons for the existence of alternative characters are discussed.
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Genetic Analysis of Chromosomal Resistance to Trimethoprim Derived from Clinical Isolates of Escherichia coli
More LessChromosomal genes conferring resistance to trimethoprim were transferred from three independently isolated thy + clinical strains of Escherichia coli to Escherichia coli K12 by using P1 transduction. Trimethoprim-resistant transductants were obtained less frequently than transductants of other chromosomal markers, suggesting that there were problems related to the expression of the trimethoprim resistance genes in E. coli K12. Mapping studies revealed that one of the resistance determinants was located at a similar position on the chromosome (1 min) to the fol-type mutations previously described in E. coli K12. The two remaining resistance determinants mapped at separate positions between 2·5 and 3 min on the chromosome. The presence of one of these determinants reduced the efficiency with which either donor or recipient cells carrying it could participate in conjugation mediated by the sex factor F and also resulted in phenotypic interaction with the azi gene. The mechanisms of trimethoprim resistance in the three clinical E. coli isolates studied were more complex and diverse than was expected from previous studies of E. coli K12 mutants.
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Mutations to Nitrofurantoin and Nitrofurazone Resistance in Escherichia coli K12
More LessThe isolation and properties of nitrofurantoin- and nitrofurazone-resistant mutants have been compared. Nitrofurantoin-resistant mutants were easier to obtain and showed a higher resistance level. There was some cross-resistance at lower drug concentrations but not at higher levels. There was no difference in the UV resistance of most of the mutants obtained although a recB strain, AB2470, did yield nitrofurantoin-resistant mutants with increased UV resistance. This was however the only repair-defective strain which could be mutated to nitrofurantoin resistance. It is suggested that there is a mechanism for nitrofurantoin resistance in Escherichia coli K12 which does not confer resistance to nitrofurazone and which may be associated with the repair of damaged DNA. This mechanism is in addition to that which also confers resistance to nitrofurazone.
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Pseudomonas sp. MT14, a Soil Isolate which Contains Two Large Catabolic Plasmids, One a TOL Plasmid and One Coding for Phenylacetate Catabolism and Mercury Resistance
More LessPseudomonas sp. MT14, isolated from soil as a result of its ability to utilise m-toluate as sole source of carbon, contains two large catabolic plasmids. One of these, pWW14, is a TOL plasmid of about 270 kb which determines the ability to grow on toluene, m-xylene and p-xylene as sole carbon sources. The other, pWW17, which is about 280 kb, determines both the ability to grow on phenylacetate and resistance to mercury salts. Growth of MT14 on benzoate results in the segregation of derivatives in which either (i) one or both plasmids are completely lost, or (ii) one or both plasmids have undergone a large deletion which results in a change in the phenotype determined by that plasmid. Deletion of about 100 kb from pWW14 results in a regulatory mutation which allows its host to grow on m-xylene but not on its metabolite m-toluate (B3 mutants). Deletion of about 95 kb from pWW17 results in loss of the ability of its host to grow on phenylacetate but the mercury resistance is not lost.
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Growth, Ultrastructure and Carotenoid Spectra of the Chlorophyll-less y-y Mutant of Chlamydomonas reinhardtii
More LessThe isolation of a stable, chlorophyll-less Mendelian mutant (y-y) of Chlamydomonas reinhardtii is described and its growth, carotenoid spectra and ultrastructure are compared to chlorophyll-containing strains. Unlike most chlorophyll-less mutants, y-y did not die in the light but grew as bright yellow colonies. It was unable to grow in a mineral medium with CO2 and it required acetate for growth. When compared to green C. reinhardtii strains, y-y grew slower in the light but at about the same rate in the dark. Light-grown and dark-grown y-y cells had no detectable chlorophyll and similar amounts of total carotenoids, which were 20–35% of the values for the green strains. The only noticeable difference in ultrastructure between y-y and the green cells was in the inner chloroplast membranes. In the light and dark y-y lacked lamellae, although the outer chloroplast membrane was retained.
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- Immunology
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Partial Purification and Characterization of Two Non K99 Mannoseresistant Haemagglutinins of Escherichia coli B41
More LessA K99− variant of Escherichia coli B41 was produced by growing the parent strain in the presence of antiserum to E. coli K12K99. Two mannose-resistant and eluting (MRE) haemagglutinins with molecular weights greater than 20 × 106 were extracted from the cell surface of the variant. One was an anionic antigen, partially purified by ammonium sulphate and isoelectric point precipitation, which adhered to calf intestinal brush borders; it was a protein composed of subunits with mol. wt 34000. Electron microscopy showed that this material did not have a regular fimbrial appearance, but contained some fine fibrillar structures. A second MRE haemagglutinin which was also partially purified by ammonium sulphate precipitation, had a definite fimbrial structure, being a protein composed of two subunits of mol. wt 49 500 and 48000. This antigen was probably responsible for the fimbrial appearance of the K99- variant, but it was antigenically distinct from the anionic adhesin and did not adhere to calf intestinal brush borders.
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- Pathogenicity And Medical Microbiology
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BCG-induced Susceptibility of Mice to Challenge with Pseudomonas aeruginosa
More LessMice infected with Mycobacterium bovis, BCG, were shown to be highly susceptible to subsequent challenge with Pseudomonas aeruginosa. The susceptibility was characterized by the enhanced mortality and shortened survival after challenge with P. aeruginosa. BCG-treated mice did not show any enhanced susceptibility to challenge with Gram-positive bacteria such as Staphylococcus aureus or Listeria monocytogenes. BCG-treated mice eliminated P. aeruginosa from their organs in a pattern similar to that in untreated mice. There was no significant difference in the bactericidal activities of polymorphonuclear cells and macrophages between BCG-treated and untreated mice. An equal amount of endotoxin was detected by the Limulus lysate assay in the blood of both BCG-treated and untreated mice after challenge with P. aeruginosa. The enhanced susceptibility induced by BCG pretreatment could be decreased when the mice were rendered LPS-tolerant by injections of small amounts of LPS. These results suggest that BCG-induced susceptibility to P. aeruginosa can be ascribed to an enhanced susceptibility to the lethal effect of LPS produced by challenge bacteria, and not to the impairment of the ability to eliminate infected bacteria.
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An in vitro System to Study Interactions between Bacteria and Epithelial Cells at the Molecular Level
More LessThis paper describes an experimental system to study interactions between porcine enterotoxigenic Escherichia coli (ETEC) and porcine intestinal epithelial cells in vitro at the molecular level. Radiolabeled bacteria or bacterial membrane fractions were incubated with brush borders prepared from purified epithelial cells, which were then washed repeatedly. The bacterial components removed by washing or retained by the brush borders were analysed to determine their composition and source. For this it was necessary to develop a minimal medium in which attachment factors of porcine ETEC could be radiolabelled. Furthermore, an improved method for the isolation of porcine intestinal epithelial cells was developed, since other procedures did not yield sufficiently pure preparations. The resulting method was rapid and yielded large quantities of viable epithelial cells, free from crypt cells and contaminating intestinal contents. Finally, we adapted existing procedures to isolate brush borders from these epithelial cells with special emphasis on the removal of nuclear and cytosolic material and on the isolation of morphologically intact brush borders. Using this system, mixtures of bacterial cytoplasmic and outer membranes were incubated with brush borders. Cytoplasmic membranes were easily removed by washing, while the outer membranes were not.
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Immunological Detection of Heterogeneous O-antigen Containing Lipopolysaccharides in Escherichia coli
More LessThe components of the cell envelopes of Escherichia coli O1: K1, O7: K1, O18: K1 and O83: K1 strains were separated on SDS-polyacrylamide gels. Longitudinal slices (50 μm thick) of the gel were incubated with typing sera for E. coli O1, O7, O18 and O83, followed by detection of the bound antibodies with 125I-labelled protein A and autoradiography. The antisera reacted with many cell envelope components of strains both with the homologous O-serotype and heterologous O-serotypes. With O-typing sera cross-reactions with heterologous cells and cells boiled for 2 h were found. Up to 40 serotype-specific bands at regular positions with molecular weights between 12000 and 100 000 were demonstrated. Since these bands were also observed when purified lipopolysaccharide and unabsorbed homologous O-typing sera were used, it was concluded that these bands represented lipopolysaccharide molecules with increasing molecular weight, all of which contained O-antigen specific immunodeterminants. The band patterns were not influenced by the growth conditions of the cells or the various isolation procedures for the cell envelopes. Comparison of various strains serotyped as O18 revealed strain differences with respect to their lipopolysaccharide band patterns. In the case of O21- and O83-serotyped strains lipopolysaccharide cross-reactions, which were detected by agglutination, were analysed in detail using the gel immunoradioassay method. These cross-reactions appeared to be caused by the presence of common determinants on their lipopolysaccharides and polysaccharide-like material. The cross-reacting antibodies could be removed by cross-absorption. It is concluded that the immunological detection of lipopolysaccharides and other components of E. coli in gels is an important tool in (1) the control of the specificity of typing antisera, (2) the study of the nature of cross-reacting antigens and (3) the study of the nature and uniformity of the various O-and K-serotypes.
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- Physiology And Growth
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The Effects of Nalidixic Acid on Respiratory Activity of Asynchronous and Synchronous Cultures of Alcaligenes eutrophus
More LessNalidixic acid inhibited DNA synthesis and cell division during asynchronous growth of Alcaligenes eutrophus but treated cells continued to grow as monitored by A 550, respiratory activity and cell volume. Differential effects on cell division were seen when the antibiotic was added at different times during synchronous growth. The earlier in the cell cycle the time of addition the greater the inhibition of cell division. These results suggests that chromosome replication is confined to the first half of the cell cycle in A. eutrophus grown at 30 °C. Respiration rates of cells selected by continuous-flow centrifugation and immediately treated with nalidixic acid increased in a stepwise fashion. These steps were similar to those observed in untreated control cells and imply that the DNA-division cycle is not the causal factor for the periodicities in respiration rates and ATPase activity that have been previously reported in this bacterium.
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The Effects of Cyanide on the Growth and Respiration of Enterobacter aerogenes in Continuous Culture
More LessThe effect of cyanide on the physiology of lactate- and oxygen-limited Enterobacter aerogenes NCTC 10336 was studied in chemostat culture (D = 0·1 h−1). In the absence of cyanide, the molar growth yield from oxygen (Y O2) under oxygen limitation was 60% of the carbon-limited value. A similar decrease in yield was observed in a lactate-limited culture (excess oxygen) which was continuously fed low concentrations of potassium cyanide. The cultures with the lower growth yields possessed respiratory systems less sensitive to inhibition by cyanide. This was particularly marked in cultures grown in the presence of cyanide. Increased cyanide resistance was associated with an increase in the concentration of a cytochrome oxidase tentatively identified as a d-type and the appearance of additional cytochromes tentatively identified as b-type.
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Properties of a Bacillus subtilis Mutant Able to Sporulate Continually During Growth in Synthetic Medium
More LessSeveral mutants of Bacillus subtilis were isolated which sporulate continually during exponential growth in glucose medium. The spdA1 mutation, responsible for the continual sporulation of one of the mutants, mapped near thr. When an exponentially growing culture of a strain containing spdA1 was maintained at essentially constant turbidity, 5% of the viable cells contained heat-resistant spores. The continual sporulation depended on the stringent response since it was absent in spdA relA double mutants. Genetic and biochemical analysis indicated that the continual sporulation of spdA1 strains was associated with a lower specific activity of pyruvate carboxylase, which limited the rate of oxaloacetate synthesis from glucose via pyruvate and thereby the supply of compounds depending on the citrate cycle, especially aspartate. Therefore, the mild stringent response caused by the spdA1 mutation seems to result from a partial deficiency of aspartyl-tRNA which may exert its sporulation-initiating effect during a limited time interval in each growth cycle. A mutant blocked in fumarase activity (citG) behaved similarly. It grew only slowly in glucose medium because much of the limiting oxaloacetate was wasted for the excretion of fumarate. The mutant produced little aspartate and sporulated at a high frequency in glucose medium, even in the presence of glutamate; the sporulation was again prevented by aspartate or malate or by introduction of the relA marker into the strain.
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Inducible and Constitutive Formation of -Fructofuranosidase (Inulase) in Batch and Continuous Cultures of the Yeast Kluyveromyces fragilis
More LessInulase production by Kluyveromyces fragilis on various fermentable and non-fermentable carbon sources was examined in carbon-limited continuous culture. Fructose and sucrose supported superior inulase yields [above 24 μmol sucrose hydrolysed min−1 (mg cell dry wt)−1 at pH 5·0, 50 °C], while some other carbon sources, including lactose, galactose, ethanol and lactate, did not stimulate inulase formation beyond basal levels. Thus fructose was identified as the primary physiological inducer. Isolation of a constitutive mutant also provided genetic evidence for the inducible nature of inulase in the wild-type. The mutant was generated spontaneously and selected in continuous culture. It produced high inulase activities in continuous culture irrespective of the carbon source. Inulase formation in the wild-type and mutant strain was further controlled by general carbon catabolite repression as suggested by enzyme yield patterns in batch and continuous culture.
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An Expanded Concept for the Glucose Effect in the Yeast Saccharomyces uvarum: Involvement of Short- and Long-term Regulation
More LessWhen Saccharomyces uvarum was cultivated in continuous culture, it exhibited the typical growth behaviour of a glucose-sensitive yeast. Metabolic changes related to glucose-repressed growth were assessed by an analysis of overall culture parameters (biomass formation, ethanol and acetate production and gas exchange rates) and by measuring the mitochondrial cytochrome content. These functions were mainly affected by the glucose effect; the steady state values of these variables were first established in the chemostat as a function of dilution rate.
The short- and long-term regulation taking place when the cells were submitted to repression was assessed by administering glucose pulses and by shifts in the dilution rate. The primary response of the cells to the initiation of repressed growth was the formation of ethanol and acetate. Since there was no repression of oxygen uptake rate or cytochrome content prior to this response, it was concluded that ethanol and acetate formation was not the consequence of repression of respiratory activity, but resulted from the regulation of pyruvate dehydrogenase and pyruvate decarboxylase activities. Long-term adaptation of the cells occurred within 24 to 48 h of the initiation of repressed growth as manifested by a decrease of mitochondrial cytochrome content to the steady state value corresponding to that of repressed growth.
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Mass Spectrometric Analysis of Drug-induced Changes in Na+ and K+ Contents of Single Bacterial Cells
More LessTime-dependent changes in the intracellular Na+/K+ ratio of Escherichia coli, induced by the nitrofuran derivative HN32 [2,4-diamino-6-(5-nitrofuryl-2)-5-ethylpyrimidine], were measured by laser-induced mass spectrometry of single bacterial cells. The results show good agreement with data on viable cell and total cell counts, release of ATP and 14CO2 production demonstrating that the single cell analysis of intracellular sodium and potassium concentrations may supply reliable information on cell viability and, furthermore, offer additional information not available from established gross methods.
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The Role of Light and an Aggregation Stimulating Factor During Aggregation of Polysphondylium violaceum
More LessLight has been shown to affect aggregation and founder cell development in the cellular slime mould Polysphondylium violaceum. An aggregation-stimulating factor, D factor, also affects aggregation of P. violaceum wild-type and aggregation-defective mutants in the complementation group aggA. Both light and D factor cause premature aggregation of amoebae and increase the number of aggregate centres formed. In addition, D factor is able to stimulate aggregation of wild-type amoebae at densities where aggregation would not normally occur. Several experiments show that amoebae are more sensitive to D factor in the presence of light, with optimum aggregation occurring in the presence of both light and D factor. Development of founder cells has been observed in the aggA mutants in the absence of D factor. However, these founder cells are inactive and do not produce aggregates until D factor is added. This class of inactive founder cells can be detected in wild-type amoebae. Production of D factor is also dependent on light with a 20- to 60-fold decrease in production over that occurring in darkness. A complex relationship between D factor, light and founder cell differentiation is established by this study.
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- Short Communication
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Straw as a Substrate for Cooperative Nitrogen Fixation
More LessInoculation of wheat straw, contained in glass columns and moistened by continuous recirculation of a solution containing mineral salts, with a cellulolytic fungus, Penicillium corylophilum, and a N2-fixing anaerobe, Clostridium butyricum, increased the decomposition rate constant from 0·0096 d−1 to 0·0139 d−1 compared with non-inoculated straw. N2 fixation during the utilization of the straw resulted in again of 11.5 mg N (g straw lost)−1 over a period of 8 weeks at 25°C.
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- Taxonomy
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A Fibril Protein Antigen Specific to Spiroplasma
More LessAn antiserum, raised in rabbits against honey-bee spiroplasma (BC3) fibril protein monomer, mol. wt 55000, excised from SDS—polyacrylamide gels, had precipitating activity against SDS-denatured fibril protein but not against the native protein. This antiserum was used to probe spiroplasma cell proteins separated by SDS—PAGE and blotted on to nitrocellulose filters. Antigens of mol. wt 55000 were identified in 13 different spiroplasmas, including a non-helical strain of Spiroplasma citri, representing five different sero-groups. The antiserum did not react with proteins in any of the Mycoplasma spp. or Acholeplasma spp. tested. Two-dimensional immunoelectrophoresis revealed variations in the amount of antigen in different isolates from the same sero-group. Peptide mapping by limited proteolysis showed that the fibril protein was highly conserved within a sero-group but that there was some heterogeneity between groups. All fibril proteins yielded common peptides recognised by the antiserum.
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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)