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Volume 33,
Issue 3,
1963
Volume 33, Issue 3, 1963
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Taxonomy of the Species Pseudomonas odorans
More LessSUMMARY: Several strains of the formerly described micro-organism then named Pseudomonas odorans Málek & Kazdová-Kožišková were examined. It was found that this organism belongs to the genus Alcaligenes. A re-descript-of the species and a discussion of its taxonomic position is given.
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The Flocculation of Suspended Matter by Paramecium caudatum
More LessSUMMARY: Paramecium caudatum has been shown to cause the flocculation of Indian ink particles. Flocculation has been demonstrated to be due to: (a) the secretion of a substance ‘P’, a carbohydrate whose monosaccharide constituents are glucose and arabinose, (b) the ingestion of particles by the cell which are then bound together by a sticky mucoprotein. Substance ‘P’ is adsorbed on to Indian ink particles present, which results in a change of their surface charge and the aggregation into floccules. Substance ‘P’ has been labelled with [14C] glucose which then appeared in the floccules.
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Isolation of Auxotrophs of Penicillium chrysogenum and their Penicillin Yields
More LessSUMMARY: As a preliminary to an investigation of the inheritance of penicillin productivity in Penicillium chrysogenum several strains were genetically labelled with nutritional deficiencies and mutant spore colours. Few auxotrophs of P. chrysogenum retained the potential for penicillin yield of their parents. An analysis suggests that when loss of penicillin production occurred in an auxotroph it was most likely due to pleiotropic effects of the single mutation to auxotrophy.
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Heterokaryon Studies and the Genetic Control of Penicillin and Chrysogenin Production in Penicillium chrysogenum
More LessSUMMARY: A method of heterokaryon isolation with Penicillium chrysogenum is described where mycelium from mixed growth of two auxotrophs was fragmented and dispersed on a medium which only supported heterokaryon growth. This method overcomes the difficulties of producing heterokaryons in this organism which are ascribed to its slow growth rate. When heterokaryons grew they sometimes gave colonies which sectored from the centre into regions which, although still heterokaryotic, had widely different conidial ratios of each component strain. The nucleus was the major component in the inheritance of penicillin production but a minor effect was exerted through the cytoplasm. The yellow pigment, chrysogenin, produced by some strains of P. chrysogenum, was inherited as a nuclear-controlled character which was not a recessive trait.
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Formation and Segregation of Heterozygous Diploids between a Wild-Type Strain and Derivatives of High Penicillin Yield in Penicillium chrysogenum
More LessSUMMARY: Heterozygous diploids were produced between a wild-type strain of Penicillium chrysogenum and two strains derived from it. The derived strains had been isolated after several and latterly divergent selection steps, selection being made at each step for higher penicillin yield. The diploids had penicillin titre values near that of the wild-type strain so that mutations for increased penicillin production which had been accumulated in the derived strains appeared in the main to be recessive. First-order segregants isolated from the heterozygous diploids were in each case predominantly of one phenotype.
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The Chemical Composition of Lambda in Paramecium aurelia, Stock 299
More LessSUMMARY: Paramecium aurelia containing λ particles was grown in an axenic medium; the λ particles were purified by passing homogenized organisms through a column of the anion exchange resin ECTEOLA. The λ particles were stained heavily with pyronin Y and weakly with the Feulgen procedure, in vivo and in vitro. Chemical analysis of the λ particles revealed that a single particle contained: 0·026 picogram (pg.) DNA, 0·230 pg. RNA, 4·0 pg. protein, 0·350 pg. carbohydrate, 5·6 pg. phospholipid. The RNA/DNA ratio in the λ particle was 8·8 as compared with a RNA/DNA ratio of 11·3 in the κ particle. Both particles contain about the same amount (0·0049 pg., and 0·0045 pg./μ3, respectively) of DNA, yet the λ particles stained very faintly with the Feulgen procedure, while the κ particles stained very heavily.
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The Cultivation of Some Rumen Oligotrich Protozoa
More LessSUMMARY: The rumen oligotrich protozoa, Eremoplastron bovis (Dogiel, 1927), E. brevispinum (Kofoid & MacLennan, 1932), Entodinium longinucleatum (Dogiel, 1925), E. ovinum (Dogiel, 1927), Eudiplodinium maggii (Fiorentini, 1889) and various Epidinium species have been cultured in mixed culture for over 7 months. The medium consisted of rice starch, dried grass and casein in a mineral salt solution + rumen liquor. No antibiotics were used. Preliminary studies showed that sodium sulphide causes inhibition of protozoal metabolism in concentrations greater than 0·01 %. Pure cultures of Epidinium ecaudatum (Fiorentini, 1889) and Eremoplastron bovis have been established. In addition, a clone of E. bovis was maintained for 5 months. A method for growing quantities of protozoa for biochemical studies is described.
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Sequential Ascus Collection in Neurospora crassa
More LessSUMMARY: A chamber has been devised to collect asci sequentially as they are ejected from individual perithecia of Neurospora crassa. Increasing age of a perithecium brought about a concurrent decrease of crossing-over. The results indicate that the exchange rates are not independent of time.
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Sensitization of Bacterial Spores to Lysozyme and to Hydrogen Peroxide with Agents which Rupture Disulphide Bonds
More LessSUMMARY: Spores of Bacillus and Clostridium species were subjected to oxidizing and reducing agents known to rupture protein disulphide bonds and to irradiation (ultraviolet; high speed electron). These treatments caused no loss of brightness of spores when viewed by phase-contrast microscopy. However, lysozyme or hydrogen peroxide caused phase darkening of treated spores and loss of dipicolinic acid typical of normal germination except that hydrogen peroxide eventually caused almost complete lysis of the spores. Under certain conditions, spore viability was unaffected during treatment with reducing agents and during subsequent phase darkening in lysozyme. Spores made susceptible to lysozyme by reducing agents became insusceptible after storage in aerated water. These reactions are compatible with Vinter's observation of the high content of disulphide bonds in the coat fraction of spores (Vinter, 1960) and with the chemical or physical rupture of these bonds. Rupture of disulphide bonds allows action of lysozyme or hydrogen peroxide on previously protected substrates. The disulphide bonds are therefore probably important in the resistance of spores to enzymes and irradiation, and rupture of these bonds may be involved in the germination process. The probable location of the lysozyme substrate in mucopeptide of the spore cortex indicates the importance of the integrity of cortex structure in maintaining the phase brightness of spores.
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An Electron Microscope Study of Root-Hair Infection by Rhizobium
More LessSUMMARY: Root hairs of clover seedlings infected by Rhizobium were studied in the electron microscope. The appearance of the infection sites supports the invagination hypothesis proposed by Nutman. The origin of the material enclosing the bacteria within the infection thread is discussed.
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Nuclear Morphogenesis During the Developmental Cycles of Some Members of the Genus Nocardia
More LessSUMMARY: Observations of nuclear morphogenesis were carried out using a modification of the acid hydrolysis-Giemsa technique. Throughout the development cycles studied, nuclear division was found to occur by means of elongation of the chromatin bodies with subsequent medial constriction and separation into daughter structures. Nuclear division greatly exceeded septum deposition during the early phases of the developmental cycles and, as a result, coenocytic filaments were formed. Fragmentation of these filaments resulted in the production of single cells, short chains and short coenocytes like those found in the inoculum. No evidence for complex nuclear fusions or reductional divisions was obtained during any period of nuclear morphogenesis and chromatin body divisions were considered to be amitotic. A simple model explaining previously reported genetic recombination in the genus Nocardia is presented.
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Studies on the Specificity of Interferon
More LessSUMMARY: The antiviral effects of chick and mouse interferons on chick and mouse cells were studied. In both systems a small amount of antiviral activity was found in the heterologous assays which varied from approximately 1 to 10 % of the homologous antiviral effect. A difference in the uptake of interferon by homologous and heterologous cells was observed which only partly explained the relative species specificity of the antiviral action of the two interferons. Destruction of interferon by supernatants from homologous or heterologous cultures could not be shown. The slopes of the dose response curves of mouse or chick interferon seemed to be significantly different and were independent of the two cell strains employed.
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Ribulose Diphosphate Carboxylase in Thiorhodaceae
More LessSUMMARY: The concentration of ribulose 1,5-diphosphate (RuDP) carboxylase, the enzyme which catalyses the conversion of ribulose 1,5-diphosphate + CO2 to 3-phosphoglyceric acid, was partially repressed in some Thiorhodaceae organisms when these were grown on certain organic compounds. Transfer of thiosulphate-grown organisms possessing a high concentration of enzyme into growth medium containing pyruvate caused a rapid decline in carboxylase activity. In the reverse situation, pyruvate-grown organisms preferentially synthesized RuDP carboxylase when transferred to growth medium containing thiosulphate alone. The presence of thiosulphate prevented loss of carboxylase with pyruvate. The incorporation pattern of 14CO2 into the ethanol-soluble compounds of organisms metabolizing thiosulphate alone was typical of autotrophic metabolism; most of the CO2 was fixed via the reductive pentose cycle. The pattern of incorporation of 14CO2 by organisms metabolizing pyruvate was strikingly different in that CO2 entered the cell constituents predominantly via a carboxylation leading to a four-carbon product. However, even under the latter conditions, the RuDP carboxylase and the reductive pentose cycle appeared to operate to some extent, since phosphoglycerate was an early product of CO2 fixation. Phosphoglycerate was an early product of 14CO2 fixation by thiosulphate-grown organisms incubated with a variety of organic substrates, showing that the carboxylase and the reductive pentose cycle could function under these conditions. The addition of thiosulphate increased incorporation of 14CO2 into phosphate esters by pyruvate-grown organisms incubated with pyruvate. It is concluded that ribulose diphosphate carboxylase and the reductive pentose cycle function in Thiorhodaceae even when grown on organic substrates; its quantitative importance was not assessed. The synthesis of the carboxylase was influenced by the growth substrate.
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Fatty Acid Requirements of Mycoplasma laidlawii
More LessSUMMARY: Several strains of Mycoplasma laidlawii were grown in a partially defined medium which contained bovine plasma albumin as the only undefined constituent. Lipid extraction of the albumin abolished its growth-promoting activity. Growth was restored by adding the extracted lipid fraction or by long-chain fatty acids. Of the fatty acids tested oleic acid was the most active in growth promotion; linoleic and linolenic acids were less active; palmitic and stearic acids were inactive. The requirement for oleic acid was satisfied by Tween 80. M. laidlawii was found to split Tween 80 enzymically, liberating free oleic acid. Replacement of bovine albumin by certain degradation products and by oleic acid, methyl oleate or Tween 80 was unsuccessful, nor could bovine albumin be replaced by several polymers known to bind fatty acids or to increase the viscosity of the growth medium.
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Osmotic Lysis of Mycoplasma
More LessSUMMARY: Various Mycoplasma strains were found to differ in their sensitivity to osmotic lysis. Three strains of the saprophytic Mycoplasma laidlawii and a strain of the parasitic M. bovigenitalium were readily lysed in media of low tonicity. Strains of the parasitic M. mycoides var. mycoides, M. mycoides var. capri, M. gallisepticum and M. neurolyticum were to a great extent resistant to osmotic lysis. The sensitivity of M. laidlawii and M. bovigenitalium to osmotic lysis markedly decreased with ageing of the organisms. M. laidlawii was more sensitive to lysis when grown in cholesterol-free media.
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Chemical Composition of Mycoplasma Cells and Membranes
S. Razin, M. Argaman and J. AviganSUMMARY: The chemical composition of whole organisms and cell membranes of eight saprophytic and parasitic Mycoplasma strains was studied. Cell membranes of M. laidlawii and M. bovigenitalium were prepared by osmotic shock. The membranes comprised about 35 % of the dry weight of the organisms. Generally the solid residue of the mycoplasmas contained 54–62 % protein, 12–20 % lipid, 3–8 % carbohydrate, 8–17 % RNA and 4–7 % DNA. Cell membranes contained 47–60 % protein, 35–37 % lipid, 4–7 % carbohydrate, and small amounts of RNA and DNA which could not be washed away with de-ionized water. The saprophytic M. laidlawii contained only one-fourth to one-third of the total cholesterol found in the lipid of the parasitic strains. No cholesterol was detected in M. laidlawii grown in cholesterol-free media. Acetone-insoluble lipids formed the major part of the lipid in the saprophytic strains, and the minor part in the lipid of the parasitic strains. The carotenoid pigments of M. laidlawii were retained in the cell membrane preparations.
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The Effect of Impure Tetanus Toxin on the Frequency of Miniature End-Plate Potentials
More LessSUMMARY: A partially purified preparation of tetanus toxin raised the frequency of the random appearance of miniature end-plate potentials in the isolated hemithorax of the mouse. The ratio of the peripheral to the central activity was increased by removing the greater part of the centrally acting tetanospasmin by specifically adsorbing the tetanospasmin out on protagon. The activation energy of the peripheral effect was 7 kcal. higher in the presence of toxin than in its absence. The peripheral effect can be neutralized with antitoxin.
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