- Volume 133, Issue 2, 1987
Volume 133, Issue 2, 1987
- Biochemistry
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Methanol and Formaldehyde Oxidation by an Autotrophic Nitrifying Bacterium
More LessThe products of incubation of Nitrosomonas europaea with methanol were studied by 13C NMR spectroscopy. The methanol was converted into formaldehyde, which was at least partially oxidized to formate. Methanol oxidation was prevented by inhibitors of the ammonia oxidizing enzyme, ammonia monooxygenase. The effects of hydrazine and NFL4 + were as found in earlier studies with other substrates for ammonia monooxygenase. From experiments in which ammonia and methanol were simultaneously oxidized, the specificity parameter k cat/K m was 0.008 for methanol, relative to unity for uncharged ammonia. The rate of growth was not enhanced by methanol, and attempts to grow the cells with methanol as energy source were unsuccessful. Formaldehyde proved much more toxic than methanol when added to shake-flask cultures. Hydroxylamine, an intermediate in ammonia oxidation, reacts with formaldehyde to form formaldoxime. Formaldoxime inhibited hydroxylamine oxidation, providing a specific mechanism for formaldehyde toxicity.
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- Development And Structure
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Role of Calcium in Assembly of the Azotobacter vinelandii Surface Array
More LessAzotobacter vinelandii grown in a defined medium lacking calcium did not exhibit the tetragonally-arranged surface layer present on calcium-sufficient cells, although each cell type possessed equivalent amounts of surface-localized S-protein. The addition of Ca2+ or Sr2+ to calcium-limited cells suspended in buffer resulted in formation of the S-layer, whereas a similar addition of Mg2+ or Be2+ did not. Incubation of cells with 35SO2− 4 during Ca2+-mediated in vivo reassembly of the S-layer confirmed that the array was formed from previously synthesized, surface-localized S-protein. Rate-zonal sedimentation of S-protein extracted from calcium-limited cells demonstrated tetrameric S-protein subunits characteristic of the native array. S-protein on the surface of calcium-limited cells was not more susceptible to iodination or proteolytic degradation than that on calcium-sufficient cells. These data suggested minimal alteration of the surface layer beyond disorganization of the S-protein subunits. Calcium limitation caused only a minor perturbation of the outer membrane and did not prevent the outer membrane from serving as a template for the in vitro reassembly of externally supplied S-protein subunits. Notably, Mg2+ or Ca2+ mediated in vitro reassembly of the S-layer and produced a layer that was more loosely attached than the native array. These data support the hypothesis that calcium is specifically required for the in vivo assembly of S-protein subunits into a tetragonal surface array.
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Involvement of Cell-surface Proteins in Sexual Cell-Cell Interactions of Tremella mesenterica, a Heterobasidiomycetous Fungus
More LessThe role of cell-surface proteins in the sexual cell-cell interactions between haploid cells of two mating types of Tremella mesenterica was studied. Gamete cells (mating-pheromone-treated cells) of the two mating types immediately associated to form large sexual agglutination complexes in a mating-type-specific manner. Vegetative cells, on the other hand, agglutinated after a lag period that corresponded to the time required for mating tube formation. Sexual agglutination was inhibited by the presence of various proteases. Polypeptides with binding activity specific for gamete cells of the opposite mating type were released from gamete cells of the two mating types by digestion with thermolysin.
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- Genetics And Molecular Biology
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Presence of Several Plasmids in the Fungus Ascobolus immersus, and Homologies with the Linear Plasmid pAl
More LessDNA analysis of several genetically unstable strains of the fungus Ascobolus immersus revealed the presence of at least seven different plasmids. These plasmids ranged from 2 to 20 kb in size, and showed homology to one of them, pA 1. In 18 stocks directly isolated from nature, two-thirds harboured plasmids ranging from 3 to 17 kb. Plasmids with homology to pAl had similar molecular masses (about 8·5 kb). A possible mechanism of plasmid formation from chromosomal DNA is discussed.
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Cloning, Characterization and Expression in Escherichia coli of a Leucine Biosynthetic Gene from Streptomyces rochei
More LessLeucine and histidine biosynthetic genes from Streptomyces rochei HP1 that complemented auxotrophic mutations in S. lividans TK54 were cloned in pIJ61. DNA from one leucine recombinant plasmid was subcloned into pBR322. From the latter, a recombinant plasmid was obtained that complemented the leuA mutation in Escherichia coli CV512 but not other leucine markers in E. coli. Analysis of this and several subclones, including mutant plasmids constructed in vitro, established that the cloned S. rochei gene was expressed in E. coli from the tetracycline promoter of pBR322 to produce a polypeptide of 67 kDa; the corresponding coding region was shown to be within a 1·7 kbp DNA fragment. Blot hybridization revealed corresponding homologous genes in several other streptomycetes.
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Isolation of a Repeated DNA Sequence from Bordetella pertussis
More LessA repeated DNA sequence in the genome of Bordetella pertussis has been demonstrated. At least 20 copies of this sequence could be observed in either BamHl or EcoRI restriction enzyme digests of chromosomal DNA; fragments carrying the repeated DNA sequence ranged in size from about 1·5 to 20 kbp. The repeated DNA sequence was cloned from two separate regions of the B. pertussis genome, as shown by restriction enzyme site maps of the two clones and by hybridization studies. A small number of differences in the pattern of hybridization of the repeated DNA sequence to chromosomal DNA from several strains of B. pertussis was observed. No repeated DNA sequences were observed in one strain each of B. parapertussis and B. bronchiseptica, and there was no hybridization of B. pertussis DNA to Escherichia coli chromosomal DNA. The repeated DNA sequence was subcloned on a 2·54 kbp BamHl fragment from one of the two original clones. Restriction enzyme digests and hybridization studies showed that the repeated DNA sequence was about 1 kbp in size and had a single, internal ClaI site.
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Isolation from Klebsiella and Characterization of Two rcs Genes That Activate Colanic Acid Capsular Biosynthesis in Escherichia coli
More LessTwo genes, designated rcs A (regulation of capsule synthesis) and rcsB, that had been cloned from the chromosome of Klebsiella aerogenes (K. pneumoniae) capsular serotype K21 were capable of activating expression of colanic acid capsular polysaccharide in Escherichia coli K12. The Klebsiella rcsA gene encoded a polypeptide of 23 kDa that was required for the induction of a mucoid phenotype at ≤30 ° but not at ≥37 °. The Klebsiella rcsB locus encoded no apparent polypeptides and was not capable by itself of causing the overproduction of colanic acid. However, when present in the same cell with rcs A, either in cis or in trans, rcsB caused expression of mucoidy in E. coli at all growth temperatures. These findings are best explained if the Klebsiella rcs A gene product acts as a positive regulator of colanic acid biosynthesis in E. coli and that activity of this protein is in turn subject to regulation by Lon protease. The Klebsiella rcsB locus may exert its effect by preferentially binding a negative regulator of capsular biosynthesis, possibly Lon itself. DNA sequences homologous to the Klebsiella K21 b rcs A and rcsB genes were found in the genomes of all other capsular serotypes of klebsiellae examined, including K2, K12, K36 and K43. However, there was no homology between such genes and the chromosome of E. coli. The ability of these rcs genes to induce a mucoid phenotype explains the apparent conjugative transfer from klebsiellae to E. coli of the ability to produce K21 or other Klebsiella capsular polysaccharides that are structurally and antigenically related to colanic acid.
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Location and Function of fruC, a Gene Involved in the Regulation of Fructose Utilization by Escherichia coli
More LessProcedures are described for the selection of Escherichia coli mutants that constitutively take up and phosphorylate fructose, and convert it to fructose 1,6-bisphosphate. The phenotype of such mutants is described. The altered regulatory gene, fruC, is highly co-transducible with leu and other markers located at min 2 on the genome. In merozygotes, fruC + is dominant to fruC. Mutants can be readily isolated that are fruC at 42 °C but fruC + at 30 °C; moreover, the integration of a Tn 10 transposon in the genome at min 2converts fruC + strains to fruC. It is therefore likely that the fruC + regulatory gene specifies a repressor protein.
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Eleetrophoretic Karyotypes and Chromosome Numbers in Candida Species
More LessThe electrophoretic karyotypes of five Candida albicans isolates and of five other Candida species have been determined, using orthogonal field alternating gel electrophoresis (OFAGE). None of the C. albicans isolates had the same electrophoretic karyotype. By comparing all five strains, we arrived at a chromosome number of nine to ten, but since the organism is diploid, we cannot distinguish genetically different chromosomes from homologues which resolve. We determined minimal chromosome numbers of 9 for Candida stellatoidea, 10 for C. glabrata and 6 for C. guilliermondii.
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- Immunology
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Immunological Characterization of an Exopolysaccharide from the Staphylococcus aureus Strain Smith Diffuse
More LessExopolysaccharides (EXPs) of Staphylococcus aureus are associated with virulence in animal models. An EXP from the S. aureus strain Smith diffuse was previously detected in 64·3 % of S. aureus clinical isolates. EXP was isolated from culture supernatants of this strain after DNAase, RNAase, phosphodiesterase I and lysostaphin treatment, and was further purified by cation-exchange and molecular-sieve chromatography. Isoelectric focusing revealed a pl of 3·6 for the EXP while the pl of teichoic acid was < 2·7. Crossed immunoelectrophoresis with homologous Smith diffuse antisera indicated that the EXP contained two immunological components. A major precipitin line persisted after the antisera had been absorbed with the non-EXP-producing variant strain, Smith compact, while the second component was removed. Tandem immunoelectrophoresis also demonstrated that the EXP was distinct from teichoic acid. The EXP contained 2-amino-2-deoxyglucuronic acid, glucose, mannose and galactose. No fatty acids or nucleic acids were present and total protein content was < 2%. Teichoic acid could not be demonstrated in the EXP, thus further substantiating the immunological studies. S. aureus EXP isolated by the present method can be used for further serological and virulence studies.
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- Pathogenicity And Medical Microbiology
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Antitumour Activity of Purified Arabinogalactan-peptidoglycan Complex of the Cell Wall Skeleton of Rhodococcus lentifragmentus
Antitumour activity of arabinogalactan-peptidoglycan (AP) complex (peptidoglycan and arabinogalactan liberated by an acid or alkaline treatment from Rhodococcus lentifragmentus AN-115 cell wall skeleton) was examined in mice and compared with that of the cell wall skeleton. The growth of syngeneic fibrosarcoma Meth A cells after implantation in BALB/c mice was significantly suppressed by AP complex, and also regressed after intratumoral injection of AP complex on days 1, 4 and 7 after tumour implantation. Although the activity of peptidoglycan was less than that of AP complex, peptidoglycan also showed both tumour-suppressive and regressive activities. Arabinogalactan did not show antitumour activity. It is interesting that peptidoglycan has an important role in the effect against tumours.
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- Physiology And Growth
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Change of l-Ascorbic Acid Content in Synchronized Cultures of Euglena gracilis
More LessThe content of total l-ascorbic acid in light-dark synchronized Euglena gracilis Z increased rapidly with illumination to reach a maximum after 7 h in the light and then decreased to reach its original level after 18 h in the dark. Total l-ascorbic acid formation was strongly dependent on illumination and was inhibited by cycloheximide, but not by chloramphenicol or streptomycin. Inhibitors of respiration and photosynthesis markedly inhibited l-ascorbic acid formation, indicating that the change of the l-ascorbic acid content may be related to the metabolic activities of mitochondria and chloroplasts.
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Properties of Monodehydroascorbate Reductase and Dehydroascorbate Reductase and Their Participation in the Regeneration of Ascorbate in Euglena gracilis
More LessThe partially purified monodehydroascorbate reductase (EC 1.6.5.4) from Euglena gracilis Z showed a pH optimum of 7·0 and a temperature optimum of 41 °C, and had an M r of 52000. Activity was threefold higher with NADPH than with N ADH; the K m values for N ADPH and NADH were 7 and 210 μm, respectively. The partially purified dehydroascorbate reductase (EC 1.8.5.1) had a pH optimum of 7·0, a temperature optimum of 38 °C and an M r of 28000. The enzyme was specific for reduced glutathione as an electron donor, with a K m of 0·85 mm, and for dehydroascorbate, with a K m of 0·26 mm. The enzyme reaction proceeded in either an ordered or a random manner. Both reductases were markedly inhibited by thiol inhibitors, and the inhibition was overcome by thiol compounds such as 2-mercaptoethanol and dithiothreitol. Both reductases were cytosolic. The activities of monodehydroascorbate and dehydroascorbate reductases could account for the regeneration of ascorbate from monodehydroascorbate and dehydroascorbate produced by ascorbate peroxidase (EC 1.11.1.11) for scavenging hydrogen peroxide.
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Further Studies on the Water Relations of Xerophilic Fungi, Including Some Halophiles
S. Andrews and J. I. PittGermination and growth of six fungi, Basipetospora halophila, Polypaecilum pisce, Aspergillus penicilloides, A. wentii, Eurotium repens and Exophiala werneckii, isolated from salt fish, and two new undescribed species from other sources, a Geomyces sp. and a Eurotium sp., were examined on media in which water activity (a w) was controlled over a wide range by glucose/fructose, glycerol or NaCl. Three species, B. halophila, P. pisce and Ex. werneckii, grew more rapidly on media containing NaCl in comparison with glucose/fructose, and hence can be considered to be halophilic. Two other species, A. penicilloides and A, wentii, were also unusually tolerant of NaCl: A. penicilloides could grow on media saturated with NaCl, while A. wentii grew more rapidly on NaCl-based media down to 0·82a w than any other xerophile examined so far. In contrast, the Geomyces sp. was intolerant of salt. The Eurotium sp. was obligately xerophilic, with growth confined to the range 0·935–0·68 a w.
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Relation between Germination, Trehalose and the Status of Water in Phycomyces blakesleeanus Spores as Measured by Proton-NMR
More LessThe distribution and properties of the cellular water in sporangiospores of Phycomyces blakesleeanus were investigated using proton-NMR. In dormant spores different classes of water were characterized by a difference in their transverse relaxation times (T 2). The amount of cytoplasmic water was estimated to be as low as about 700 mg (g dry wt)−1 and its small T 2 (18·2 ms) indicated a very limited mobility. About 10 min after induction of germination (by a heat shockor by addition of 0·1 m-acetate), both the content and the mobility of the cytoplasmic water increased sharply. These changes coincided with a rapid breakdown of most of the cellular trehalose and with the production (and leakage from the spores) of large amounts of glycerol. The role of these biochemical changes is discussed in relation to the water status of the spores.
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Effects of Water Activity on Growth and Sporulation of Paecilomyces farinosus in Liquid and Solid Media
More LessThe effects of water activity on colony radial growth rate, specific growth rate, growth yield and blastospore production of Paecilomyces farinosus were studied. The compound (PEG 200) used to adjust water activity was not used for growth either when it was the sole carbon source in the medium or when the medium also contained glucose. Daily additions of water were made to cultures ‘compensated’ cultures) to compensate for evaporation; when this was not done the water activity of the medium decreased during incubation and a water activity at which growth ceased was eventually attained. A correlation was observed between the inhibitory effects of water activity on specific growth rate (µ) in ‘compensated’ shake flask cultures and on colony radial growth rate (K r) on solid medium. Thus, K r can be used to assess the effects of water activity on mould growth. Growth yield decreased linearly with decrease in water activity, and a decrease in water activity from 0·985 to 0·958 caused an approximately sixfold increase in the yield of blastospores per unit biomass dry weight.
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Lack of Pleiotropic Compensation in Extracellular Protein Production by Hypoproducing Variants of Staphylococcus simulans biovar staphylolyticus
More LessThe changes in bacterial density, total extracellular protein and activities of three extracellular enzymes were monitored during growth of wild-type Staphylococcus simulans biovar staphylolyticus, a representative pleiotropic variant that produced decreased levels of the three extracellular enzymes, and a variant that produced only 5 of the 14 extracellular proteins secreted by the wild-type organism. Both variants produced less total extracellular protein than did the parental organism. SDS-PAGE of the proteins secreted by these hypoproducing variants showed that all of the extracellular proteins were produced in decreased amounts. No pleiotropic compensation in extracellular protein production was observed for these hypoproducing variants of S. simulans biovar staphylolyticus.
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The Roles of Osmotic Stress and Water Activity in the Inhibition of the Growth, Glycolysis and Glucose Phosphotransferase System of Clostridium pasteurianum
More LessGrowth of Clostridium pasteurianum was inhibited in media of high solute content. At equal osmolarities, permeant solutes (glycerol and acetamide) were much less growth-inhibitory than non-permeant solutes (KC1 and xylitol). Glycolysis by washed cell suspensions was inhibited by these solutes in parallel with growth. However, in their inhibition of glucose 6-phosphate dissimilation by permeabilized cells the distinction between permeant and impermeant solutes was significantly less marked. The glucose phosphotransferase system (PTS) of intact cells was much more strongly inhibited by non-permeant than by permeant solutes. It was concluded that the predominant inhibitory effects on this organism of media of high solute content are due not to the low water activity of such media per se, but to the creation of an osmotic pressure across the bacterial cytoplasmic membrane, which acts to inhibit the glucose PTS by which the organism effects glucose uptake. Parallel measurements of the effects of xylitol on both glycolysis and the activity of the glucose PTS suggested that despite this correlation between the osmotic inhibition of growth, glycolysis and the PTS, the flux-control coefficient of the PTS on glycolysis did not exceed 0.2 under the conditions used.
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Degradation of Eighteen 1-Monohaloalkanes by Arthrobacter sp. Strain HA1
More LessFour coryneform bacteria were isolated from enrichments with 1-chlorobutane, 1-chloropentane or 1-chlorohexane as sole source of carbon and energy. One organism, strain HA1, was identified as an Arthrobacter sp. It could utilize at least 18 1-chloro-, 1-bromo- and 1-iodoalkanes, but not the 1-fluoroalkane tested. Substrate utilization was quantitative and growth yields of about 5.5 g protein (mol C)−1 were observed for hexanol and 1-chlorohexane with specific growth rates of 0·19 and 0·14 h−1, respectively. The organohalogen atom was released quantitatively as the halide ion. Cells grown on 1-chlorobutane contained an inducible enzyme(s) that dehalogenated haloalkanes. The enzyme was soluble, required no cofactors, membrane components or oxygen for activity, and released halide and the corresponding n-alcohol from the 1-haloalkane. The halidohydrolase(s) in crude extract had a specific activity of about 0·7 mkat (kg protein)−1 and dehalogenated a much wider spectrum of compounds (at least 29, including mid-chain and α,ω-dichlorosubstituted alkanes) than supported growth.
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Regulation of the Intracellular Location of Methane Mono-oxygenase During Growth of Methylosinus trichosporium OB3b on Methanol
More LessThe methane-oxidizing bacterium Methylosinus trichosporium OB3b retains the capacity to express two types of methane mono-oxygenase (MMO) during growth on methanol in continuous culture. Soluble MMO predominates during copper-limited growth whilst particulate (membrane-bound) MMO activity is expressed fully only in copper-sufficient cultures. Organisms containing soluble MMO oxidized ethylbenzene (an artificial substrate for soluble but not particulate MMO) but this capacity was progressively lost when additional copper was made available to the organism, and MMO activity was transferred to the particulate fraction of cell-free extracts. Although intracellular location of MMO is apparently regulated by copper availability during growth on both methane and methanol, whole-cell MMO activities are appreciably higher during growth on the former (natural) carbon source.
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Synchronous Akinete Germination and Heterocyst Differentiation in Anabaena PCC 7937 and Nostoc PCC 6720
More LessIsolates of the filamentous cyanobacteria Anabaena PCC 7937 and Nostoc PCC 6720 were selected in which the germling extruded from the akinete coat at the single cell stage and in which heterocyst differentiation occurred at the two or three cell stage after germination in the absence of combined nitrogen. The process of heterocyst differentiation of these germinating akinetes was synchronous and highly reproducible, and it resulted in transient yields of mature heterocysts exceeding 35% of the total cell population.
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The Osmotically Regulated proU Locus of Salmonella typhimurium Encodes a Periplasmic Betaine-binding Protein
More LessThe proU locus of Salmonella typhimurium encodes an osmotically induced betaine transport system. We have identified a 31 kDa periplasmic protein, encoded by proU, whose synthesis is induced by osmotic stress. A specific betaine-binding activity with a K D of about 1 m is also present in the periplasm of osmotically induced cells. This activity is absent in those proU mutants which lack the 31 kDa periplasmic protein. Thus, ProU is a periplasmic binding-protein-dependent transport system.
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2-Phenylethylamine Catabolism by Escherichia coli K12
More LessEscherichia coli K12 grows on 2-phenylethylamine as sole carbon and energy source by converting it, via phenylacetaldehyde, to phenylacetic acid. Phenylacetaldehyde was formed by the action of an inducible amine oxidase and catalase activity was increased sixfold, presumably to ensure removal of the H202 that was expected to be a product of the amine oxidation. The phenylacetaldehyde was oxidized to phenylacetic acid by an inducible NAD+-dependent dehydrogenase. Mutants defective in phenylacetaldehyde dehydrogenase cannot grow on 2-phenylethylamine as carbon and energy source but can still use it as a nitrogen source.
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Co-adaptation of Escherichia coli and Coliphage λvir in Continuous Culture
More LessPopulations of the bacterium Escherichia coli and of its phage λvir appeared to equilibrate in continuous cultures. The bacterial end-populations were heterogeneous in respect of their resistance to λvir and their ability to utilize maltose. The most competitive of the selected bacteria were mutants which had a reduced rate of synthesis of λ-receptor so as to become highly, but not totally, resistant to the phage. The coexisting phage had an increased affinity for the receptor and an altered antigenic specificity, suggesting adaptation of its adsorption site in response to the evolution of resistance in the bacteria.
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Glucose and Penicillin Concentrations in Agar Medium Below Fungal Colonies
More LessThe growth of colonies of Rhizoctonia cerealis and Penicillium chrysogenum on solid media in plate cultures was studied. When grown on defined media containing 10–50 mm-glucose, R. cerealis did not cause a significant reduction in the glucose concentration of the medium in advance of colonization, but did cause the formation of a steep glucose concentration gradient in the substrate below the colony; the medium directly below the centre of a 7 cm diameter colony of R. cerealis was exhausted of glucose even when the fungus was grown on medium containing 50 mm-glucose. Penicillin produced by colonies of P. chrysogenum accumulated in the medium in advance of fungal colonization. For a period up to about 18 d after inoculation, the concentration of penicillin in the medium throughout the plate increased with colony development and thereafter, except at the margins of the plate, decreased.
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The Influence of Ammonium Permease Activity and Carbon Source on the Uptake of Ammonium from Simple Defined Media by Saccharomyces cerevisiae
More LessWhen growing under defined conditions, cells of the yeast Saccharomyces cerevisiae absorbed ammonium more rapidly with glucose as carbon source than with maltose. Ammonium pool sizes and permease activity were also higher in the glucose-grown cells and the relationship implies that firstly, the sugar is a primary determinant of ammonium permease activity and, secondly, the activity of the permease largely determines both the rate of ammonium uptake and ammonium pool size in the first part of the fermentation.
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An Unusual Hexose-ATP-Kinase with Two Catalytic Sites and a Role in Carbon Catabolite Repression in the Yeast Schwanniomyces occidentalis
More LessThe hexose-ATP-kinase of wild-type Schwanniomyces occidentalis (CBS 819) is, like hexokinase PII of Saccharomyces cerevisiae, associated with carbon catabolite repression and phosphorylates d-glucose and d-fructose. The kinase of Schw. occidentalis repression-resistant (DogR) mutants phosphorylates d-glucose, but not d-fructose. Subjecting the wild-type enzyme to 45 °C for a few minutes appears to alter its activity, specificity and kinetic characteristics to that of the mutant enzyme. Fast protein liquid chromatography, with anion-exchange or gel-filtration columns, gel-electrophoresis, and DNA hybridization with the hexl r mutant of the HXK2 (hexokinase PII) gene of Sacch. cerevisiae, all failed to resolve more than one hexose-ATP-kinase in Schw. occidentalis. Hence Schw. occidentalis appears to have a single hexose-ATP-kinase, M r ∼ 72000, with two catalytic sites, analogous to the aspartate kinase/homoserine dehydrogenase of Escherichia coli. One site is hexokinase-like and associated with catabolite repression and the other is glucokinase-like. Values for apparent K m were 7·2 mm-d-fructose and 0·55 mm-d-glucose (hexokinase site) and 0·078 mm-d-glucose (glucokinase site).
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Production and Activation of an SDS-resistant Alkaline Serine Exoprotease of Vibrio alginolyticus
More LessVibrio alginolyticus produced an extracellular SDS-resistant protease (protease A) with an apparent M r of approximately 54000 when cultured in complex, proteinaceous media. Ca2+ was required for the activation and stability of this protease. Its activity was inhibited by EDTA and a serine protease inhibitor, but was not affected by an inhibitor of trypsin-like enzymes. Optimum protease activity occurred under alkaline conditions. Two SDS-resistant exoproteases, B and C, with apparent M r values of approximately 41000 and 37000 respectively, were also produced in complex proteinaceous media. Dialysis of cell-free supernatant samples, which contained predominantly protease A, against distilled water, resulted in increased B and C activity. Production of protease A, B and C activities was inhibited by o-phenanthroline, quinacrine and lack of aeration.
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The Role of Glucose in the pH Regulation of Germ-tube Formation in Candida albicans
More LessIt has been reported that Candida albicans can form germ-tubes only in the narrow pH range of 6–8, and that by changing only the pH one can regulate germ-tube formation. We found that the pH minimum for germ-tube formation could be dramatically lowered by eliminating the glucose present in many induction solutions. Lee’s medium lacking glucose, ethanol, N-acetyl-d-glucosamine, and proline induced germ-tubes at pH values as low as 3 under most conditions. The presence of as little as 1 m-glucose in these induction solutions was sufficient to cause the cells to grow either as yeasts with multiple buds or as pseudohyphae when the pH was 3·7. However, when C. albicans was grown in any of the above induction solutions (with the exception of ethanol), containing 200 mm-glucose buffered at pH 5·8, not only were germ-tubes formed, but their rate of formation and length were also increased. Preincubation of the cells in a solution buffered at pH 3·7 and containing 200 mm-glucose, before exposure to induction solutions lacking glucose at pH 3·7 or at pH 5·8, did not inhibit germ-tube formation. Likewise, addition of glucose after 45 min exposure to an induction solution was without effect. Theophylline and dibutyryl cAMP did not counteract the action of glucose. Other sugars which suppressed germ-tube formation at low pH were fructose, galactose, mannose, xylose, gluconic acid and the nonmetabolizable sugar 3-O-methylglucose. These results indicate that pH does not directly regulate dimorphism in C. albicans, and that glucose or its metabolites may play an important role.
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Establishment of the Steady State in Glucose-limited Chemostat Cultures of Klebsiella pneumoniae
More LessTo investigate the relationship between growth rate and concentration of the nutrient that limits growth, ‘Klebsiella aerogenes’ NCTC 418 (K. pneumoniae) was grown in a glucose-limited chemostat. The actual time required to establish a steady-state glucose concentration exceeded that expected theoretically. Apparently, there is a long-term adaptation of the cells to nutrient limitation. As yet, it is not clear whether this has a phenotypic or genetic origin. In the final steady state, the dependence of the growth rate on glucose concentration could be mathematically described equally well by a hyperbolic and by a logarithmic function.
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- Systematics
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Systematic Analysis of the Long-chain Components of Eubacterium lentum
More LessThe cellular long-chain component patterns of 33 strains of Eubacterium lentum were determined by gas chromatography. Two main types of long-chain component patterns were distinguished. The first (26 strains) was characterized by saturated branched-chain fatty acids (brl4:0, br 15:0, br16:0 and br17:0). The second (7 strains) did not contain branched-chain fatty acids and was characterized by saturated straight-chain fatty acids (11:0,12:0, 14:0 and 16:0). Both types contained fatty aldehydes and their respective dimethyl acetals (14ald and 14dma, 16ald and 16dma). brl6dma was only found in the first type. The G + C content of the DNA (T m) of the 33 strains varied between 63·7 and 69·1 mol %. Canonical correlation analysis distinguished three subtypes within the first main type.
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Taxonomic Studies on Some Gram-negative Methylotrophic Bacteria
More LessOne hundred and fifteen cultures, including obligate, restricted facultative and facultative methylotrophs and members of possibly related taxa, were tested for 135 characters based on morphology, physiology and biochemistry and the results were subjected to computer analysis. The polar lipid composition of all the strains was examined. The isoprenoid quinone composition and the mol% G + C value of the DNA were determined for all the obligate and restricted facultative bacteria, and also for some of the other strains representative of the clusters formed in the numerical taxonomic study. The results indicate that the obligate methanol-utilizing bacteria all exhibit a high phenotypic similarity and are taxonomically distinct from the restricted facultative and the facultative methanol-utilizing bacteria examined and from the pseudomonad reference strains. The results also indicate that the obligate methylotrophs and the restricted facultative methylotrophs represent two distinct taxa of generic status: Methylobacillus and a taxon which can be equated with the organisms currently referred to as ‘Methylophilus’.
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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)