- Volume 97, Issue 2, 1976
Volume 97, Issue 2, 1976
- Biochemistry
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The Relationship Between the Uptake of Glucose and 3-O-Methylglucose and Soluble Carbohydrate and Polysaccharide in the Fungus Dendryphiella salina
More LessSummary: When mycelium of Dendryphiella salina, pre-incubated in D-[1-14C] mannitol such that this is the only major labelled soluble carbohydrate present, absorbs glucose or the non-metabolized sugar 3-O-methylglucose, there is a specific stimulation of incorporation of 14C into alkali-insoluble, trichloroacetic-acid-soluble (1 → 4)-α-glucan, probably glycogen. There is also a net increase in the amount of glucan caused by stimulation of synthesis and inhibition of breakdown. Addition of 3-O-methylglucose results in the loss of mannitol into the medium. This loss and the reduced rate of replenishment from the glucan is important in the osmotic regulation of the hyphae. If osmotic adjustment does not occur, the hyphae do not show the specific incorporation of 14C into the glucan.
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Proteolytic Activation and Inactivation of Chitin Synthetase from Mucor rouxii
More LessSummary: Crude chitin synthetase preparations from the mycelial and yeast forms of Mucor rouxii behaved differently. The mycelial preparations, incubated at 28 °C, lost virtually all chitin synthetase activity in a few hours; by contrast, the activity of enzyme preparations from yeast cells increased several fold during similar incubations. These spontaneous changes were probably caused by endogenous protease(s). Seemingly, the chitin synthetase in yeast preparations was present mainly in a latent, ‘zymogenic’, form that was activated by proteases. In the mycelial preparations, chitin synthetase was present mainly in an active state and was rapidly degraded by endogenous proteolysis. Exogenous proteases accelerated activation and destruction of chitin synthetase; an acid protease from Rhizopus chinensis was the most effective activator. The activation of chitin synthetase was inhibited by a soluble protein in the cell-free extract. Treatment with the detergent Brij 36T stabilized the chitin synthetase of crude preparations against spontaneous changes. Stabilized preparations were rapidly activated by exogenous proteases. The different behaviour of chitin synthetases in crude extracts of mycelium and yeast cells is consistent with, and perhaps partially responsible for, the differences in wall construction between mycelial and yeast forms of M. rouxii.
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Cellulolytic Enzymes in Culture Filtrates of Rhizoctonia lamellifera
More LessSummary: During growth in a liquid culture containing a single soluble or an insoluble cellulosic carbon source, Rhizoctonia lamellifera released cellulolytic enzymes into the medium. These enzymes were separated by gel filtration and ion-exchange chromatography into seven components, three of high and four of low molecular weight. One of the components had the character of a C1 cellulase. When the components were combined they released more reducing sugars from cellulosic substrates than when used singly.
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Growth on d-Lyxose of a Mutant Strain of Escherichia coli k12 Using a Novel Isomerase and Enzymes Related to d-Xylose Metabolism
More LessSummary: Escherichia coli k12 cannot grow on d-lyxose, but a mutant was isolated which can utilize d-lyxose as sole source of carbon and energy for growth. d-Lyxose is transported into the bacteria by the d-xylose permease. The mutant constitutively synthesizes a new isomerase which is not inducible in the parent strain under any of the conditions tested. This enzyme, whose native substrate appears to be d-man-nose, fortuitously converts d-lyxose into d-xylulose. Its structural gene is located at around 85 min on the E. coli genetic map, away from other known isomerase genes. d-Xylulose is subsequently catabolized by the enzymes of the normal d-xylose metabolic pathway. d-Mannose isomerase was partially purified and some of its properties were examined.
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Carbon Assimilation by Claviceps purpurea Growing as a Parasite
More LessSummary: Carbon assimilation by Claviceps purpurea, growing as a parasite on cereals, has been investigated by supplying the host plant with 14CO2 in a closed system. The presence of the pathogen induced the plant to exude photosynthate which contained high levels of sucrose. During the period of 14CO2 supply, 14C was incorporated into the sucrose and so the path of carbon into the parasite could be traced. Hexoses, derived by the action of the fungal sucrase on sucrose, were assimilated by the pathogen and largely converted into polyols - mainly mannitol and, to a lesser extent, trehalose. The rate of carbohydrate metabolism decreased with maturation of the ergot, and also showed qualitative differences between the basal and apical regions of the ergot which were probably a function of nutrient supply.
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Rhodanese from Thiobacillus a2: Catalysis of Reactions of Thiosulphate with Dihydrolipoate and Dihydrolipoamide
More LessSummary: Rhodanese (thiosulphate: cyanide sulphurtransferase EC. 2.8.1.1) was purified 25- to 30-fold from thiosulphate-grown Thiobacillus A2. It exhibited a pH optimum between pH 10·2 and 10·4 and apparent K M values of 0·36 mm-Na2S2O3 and 17 mm-KCN. Ultraviolet spectrophotometry and thin-layer chromatography showed that the enzyme catalysed the reaction of S2O3 2− with dihydrolipoic acid or dihydrolipoamide, producing α-lipoate or lipoamide, with the intermediate production of the persulphides of dihydrolipoate and dihydrolipoamide, which were demonstrated chromatographically. This is the first demonstration of catalysis by a thiobacillus rhodanese of reactions which are likely to be physiologically important in the oxidative dissimilation of thiosulphate by a central energy-conserving pathway.
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Rhodanese from Thiobacillus a2: Determination of Activity by Proton Nuclear Magnetic Resonance Spectroscopy
More LessSummary: Rhodanese from Thiobacillus a2 was shown by proton nuclear magnetic resonance (NMR) spectroscopy to use dihydrolipoate or dihydrolipoamide as acceptor of the sulphane moiety of thiosulphate with the formation of α-lipoate or lipoamide respectively. Correlation is shown between assays of the enzyme activity by NMR spectroscopy and by ultraviolet spectrophotometry.
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Immunofluorescence Detection of Nitrogenase Proteins in Whole Cells
More LessSummary: Fluorescent antibodies (FA) prepared against the Mo-Fe and Fe proteins of nitrogenase from Klebsiella pneumoniae m5a1 were used to detect these protein components in toluene-treated whole cells that were actively reducing acetylene. The FA were highly specific, staining only nitrogenase component proteins originating from Klebsiella. Cross-reactions between the FA and purified nitrogenase proteins from other dinitrogen-fixing micro-organisms did not occur, except in the case of Bacillus polymyxa. The tests rapidly and accurately assayed the component proteins in Klebsiella mutants and derivatives to which Klebsiella nif genes had been transferred either by plasmid or by other means. Cross-reactions also indicated the degree of relatedness between nitrogenase proteins from dinitrogen-fixing micro-organisms of various origins.
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Activities of some Enzymes Involved in Metabolism of Carbohydrate during Sporophore Development in Coprinus cinereus
More LessSummary: Measurements of the specific activities of representative enzymes of the pentose phosphate cycle, Embden-Meyerhof-Parnas (EMP) pathway and the tricarboxylic acid (TCA) cycle in Coprinus cinereus sporophores at different stages of development indicate that glycolysis is the major route of carbohydrate catabolism throughout sporophore development. Enzymes of the pentose phosphate cycle were always at lower specific activities than the enzymes of the EMP pathway, and the activities of the pentose phosphate cycle enzymes declined drastically as development proceeded. This conflicts with the findings for Agaricus bisporus, but the changes in some enzymes were qualitatively similar to those occurring in the development of sporophores of Schizophyllum commune. A number of enzymes of the TCA cycle were detected, but there was no 2-oxoglutarate dehydrogenase activity nor increase of isocitrate lyase activity over the basal repressed level. However, glutamate decarboxylase and 4-aminobutyrate aminotransferase were detected, suggesting that the inoperative 2-oxoglutarate dehydrogenase is by-passed through the glutamate decarboxylation loop. The results are discussed in relation to the changes which also occur in the specific activities of the two glutamate dehydrogenase enzymes during development of the sporophore.
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- Development And Structure
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A Function for the Plasmalemma Grooves of a Fission Yeast
More LessSummary: Ultrastructural studies on regenerating protoplasts of Schizosaccharomyces pombe show that the spatial differentiation of the plasmalemma into grooves and flat areas is reflected in a functional differentiation in cell-wall synthesis. The grooves are the initial site of production of wall fibrils.
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Plasma Membrane Ultrastructural Differences Between the Exponential and Stationary Phases of Saccharomyces cerevisiae as Revealed by Freeze-Etching
More LessSummary: Ultrastructural changes in the plasma membrane of Saccharomyces cerevisiae during the exponential and stationary growth phases were studied by freeze-etching. In the exponential phase, plasma membrane-intercalated particles were distributed randomly. In the stationary phase, several areas of the plasma membrane showed a hexagonal arrangement of particles; these areas appeared to increase with the age of the culture. The polarity of the particles also changed partially: the E-face of the plasma membrane was only sparsely embedded with particles in exponential phase cells, but relatively densely embedded in stationary phase cells. Invaginations of the plasma membrane on the P-face were devoid of particles during both growth phases. Invaginations of the E-face were sparsely embedded with particles in exponential phase cells, but densely embedded with particles in stationary phase cells.
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- Genetics And Molecular Biology
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Mutants of Escherichia coli K12 Unable to use Fumarate as an Anaerobic Electron Acceptor
More LessSummary: Mutants of Escherichia coli k12 strain WGAS-GF+/LF+ were selected for their inability to use fumarate as terminal electron acceptor for supporting growth on glycerol or lactate in an atmosphere of H2 plus 5% CO2. Eighty-three mutants were grouped into seven different categories according to their ability to grow on different media and their ability to produce gas during glucose fermentation. Enzymological and genetic studies indicated that the major class (type I), representing nearly 70% of the isolates, lacked fumarate reductase and corresponded to the frdA mutants studied previously ( Spencer & Guest, 1973, 1974 ). Members of a second class (type II) were phenotypically similar to men mutants, blocked in menaquinone biosynthesis. They differed from menA mutants in having lesions in the 44 to 51 min region of the chromosome rather than at 87 min. It was concluded that fumarate reductase and menaquinone are essential for anaerobic growth when fumarate serves as electron acceptor but not when nitrate performs this function. Fumarate reductase and menaquinone are also essential for H2-dependent growth on fumarate. Type III mutants, originally frdB, were designated fnr because they were defective in fumarate and nitrate reduction and impaired in their ability to produce gas. The fnr gene was located at 28·5 min by its cotransducibility with pyrF (5·7 to 9·2%) and trpA (2·7 to 5·7%) and the gene order fnr-qmeA-pyrF-trpA was established. It was not possible to assign specific metabolic lesions to the fnr mutants nor to the remaining classes, which all exhibited pleiotropic phenotypes. Nevertheless, the results demonstrate that functional or organizational relationships exist between the fumarate reductase system, nitrate reduction and hydrogen production.
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Competence in Continuous Cultures of Bacillus subtilis: Inhibition by Arginine and Reversal of the Inhibition by Mn2+
More LessSummary: Arginine inhibited the competence of Bacillus subtilis growing in a chemostat at a dilution rate of 0·277 h−1. The biosynthesis of competence-stimulating activity was only partially repressed. The inhibitory effect may be due to an alteration in the cell’s capacity for being stimulated to competence and/or in its ability to take up DNA irreversibly. MnSO4 at 10−6 m restored competence immediately.
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- Physiology And Growth
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Mitosis, Septation, Branching and the Duplication Cycle in Aspergillus nidulans
More LessSummary: Mitosis, septation and branching were studied in undifferentiated mycelia and leading hyphae of Aspergillus nidulans, a mould which forms incomplete septa. After spore germination, nuclei divided synchronously until germ-tube hyphae contained 8 or 16 nuclei; mitosis occurred when the volume of cytoplasm per haploid nucleus was about 60 μm3. Intercompartment development was not synchronized, consequently mitosis in the mycelium as a whole eventually became asynchronous. During the stage of asynchronous compartment development, the nuclei, septa, branches and total length of undifferentiated mycelia all increased exponentially at approximately the same specific rate.
Septa were formed in hyphae in groups of up to nine; the mean time required for the formation of a group of septa was about 9 min. The mean interval between successive cycles of septation in a hypha was approximately the same as the organism's doubling time. There was a highly significant correlation coefficient between septation and branch initiation and most intercalary compartments initially formed a single branch.
The volume of cytoplasm per nucleus in a diploid strain was approximately double the value observed for a haploid strain. However, the length of the hyphal growth unit was not affected by ploidy.
The study suggests that a duplication cycle can be recognized during mycelial growth which is analogous to the cell cycle observed in unicellular micro-organisms.
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Nuclei, Septation, Branching and Growth of Geotrichum candidum
More LessSummary: A study was made of growth, septation and branching in Geotrichum candidum, a mould which forms physiologically complete septa. A correlation was observed between septation and branch initiation; branches were almost invariably formed just behind septa. Primary branches and their parent intercalary compartments initially increased in length at an exponential rate before eventually attaining a constant rate of extension. The whole branching system (which eventually contained seven tips) produced by an intercalary compartment increased in length exponentially until it attained a total length of at least 1·5 mm.
The total length and the number of nuclei of undifferentiated mycelia increased exponentially at the same specific growth rate. The results suggest that nuclei divide just before or just after arthrospore formation.
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Macromolecular Syntheses during the Cell Cycles of Yeast and Hyphal Phases of Candida albicans
More LessSummary: Synchronous cultures of yeast and hyphal phases of Candida albicans showed exponential increases in RNA content and stepwise exponential increases in DNA content. The periods of DNA synthesis in the two phases coincided with one another and with the budding peaks of the yeast phase. Hyphae grown in synchronous cultures also showed an exponential increase in length. The hyphal phase was therefore normal.
Hyphal nuclear division occurred after hyphal DNA synthesis. Germination was a unique event for a hypha and unlike yeast bud formation, preceded the first period of DNA synthesis.
The exponential increase in RNA and DNA in asynchronous cultures of hyphae in serum paralleled the exponential increase in the numbers of cells in asynchronous cultures of yeasts in defined media. Thus there are no factors in serum which inhibit the normal exponential growth of C. albicans.
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A Chemically-defined Medium for the Growth of a Ureolytic Strain of Streptococcus faecium
More LessSummary: A chemically-defined medium was developed which supported growth of Streptococcus faecium and permitted synthesis of urease. This streptococcus cannot utilize ammonia and needs a complex medium, but its requirements are probably provided in the rumen. The specific activity of urease was inversely related to growth and in no medium was there high growth and high urease activity. Anaerobic culture and the presence of urea in the medium were essential for urease activity, but not for growth.
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Regulation of the Tricarboxylic Acid Cycle and Poly-β-hydroxybutyrate Metabolism in Azotobacter beijerinckii Grown under Nitrogen or Oxygen Limitation
More LessSummary: Azotobacter beijerinckii was grown in ammonia-free glucose/mineral salts media in chemostat culture under oxygen or nitrogen limitation. Selected enzymes of the tricarboxylic acid cycle and poly-β-hydroxybutyrate metabolism were monitored in relation to oxygen supply for both steady and transition states. Two dissolved oxygen concentrations were used for the nitrogen-limited steady state to investigate the possible effects of respiratory protection of nitrogenase on these enzymes. The levels of NADH oxidase, isocitrate dehydrogenase and 2-oxoglutarate dehydrogenase increased markedly on relaxation of oxygen limitation while pyruvate dehydrogenase and citrate synthase were relatively unaffected. β-Ketothiolase and acetoacetyl-CoA reductase levels decreased as oxygen limitation was relaxed. Respiratory activity, as measured by the Q o2 value, increased with oxygen supply rate. Imposition of oxygen limitation on a nitrogen-limited culture caused an immediate increase in the NADH/NAD ratio but this rapidly readjusted to its previous steady-state value. These changes are discussed in relation to respiratory protection of nitrogenase and poly-β-hydroxybutyrate metabolism in A. beijerinckii.
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- Short Communications
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- Taxonomy
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Numerical Taxonomy of some Yellow-pigmented Bacteria Isolated from Plants
More LessSummary: Phenetic data on over 60 heterotrophic, Gram-negative, yellow chromogenic bacteria from plant material were collected and analysed using numerical taxonomic methods. Marker strains representing 42 taxa were included in the analyses. At similarity levels of 80% or above, eight distinct clusters were obtained, the first four of which included yellow chromogens. Cluster 1 contained isolates from green healthy leaves of Agrostis tenuis, Festuca rubra, Holcus lanata, Lolium perenne and Poa pratensis, and clusters 2 and 3 consisted of isolates from Holcus lanata seeds and leaves of P. pratensis respectively. Cluster 4 contained seven subgroups and was equated with the family Enterobacteriaceae. Erwinia herbicola strains from a variety of sources formed a homogeneous subgroup, readily distinguishable from authentic strains of E. amylovora, E. carotovora, other representative erwiniae, and from all other enterobacteria studied. These data emphasize the heterogeneous nature of yellow-pigmented bacteria from plants, and support the inclusion of E. herbicola and other Erwinia species in the Enterobacteriaceae.
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- Corrigendum
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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 2 (1948)
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Volume 1 (1947)