- Volume 13, Issue 2, 1955
Volume 13, Issue 2, 1955
- Article
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The Action of Streptococcal Amylase in relation to the Synthesis of an Amylosaccharide by Amylolytic Strains of Streptococcus pyogenes
More LessSummary: Streptococcal amylase behaves like α-amylase, causing branch-chained substrates to lose viscosity with minimal release of reducing groups, and to become achromic with iodine. Reducing values equivalent to 50 % of the theoretically obtainable maltose were reached after prolonged hydrolysis.
The enzyme was produced in high concentration by amylase-positive streptococci growing in simplified medium containing substrate. The same strains synthesized a starchy cell substance if grown in plasma-enriched medium containing either maltose or glycogen. When extracted by boiling with weak alkali the new product resembled amylose.
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The Formation of a Starch-like Polysaccharide from Maltose by Strains of Streptococcus pyogenes
More LessSummary: Certain strains of Streptococcus pyogenes produced a starch-like substance in the presence of maltose and plasma. Amylolytic strains of group A streptococci produced larger amounts of the substance than other strains of these organisms. The substance was elaborated in the presence of optimal concentrations of plasma, with either starch, glycogen or maltose in the medium. It was not produced when either glucose-1-phosphate, glucose, cellobiose, melibiose, saccharose or lactose was substituted for maltose.
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Tricarboxylic Acid Cycle Reactions in the Fungus Zygorrhynchus moelleri
More LessSummary: Whole cells of the fungus Zygorrhynchus moelleri can oxidize acetate, cis-aconitate, citrate, fumarate, glucose, malate, α-ketoglutarate, pyruvate, and succinate under appropriate conditions. The rates of oxidation of acetate and succinate, in particular, are very high and exceed the rate of glucose oxidation. Diethylmalonate in high concentration inhibits the oxidation of glucose and acetate, but succinate oxidation is not greatly inhibited by malonic acid, even when the malonate concentration is twice the succinate concentration.
By freezing the cells in liquid nitrogen it is possible to investigate many of the individual reactions of the tricarboxylic acid cycle. Among the more important reactions shown were: cis-aconitate to citrate; citrate or cis-aconitate to α-ketoglutarate; α-ketoglutarate to succinate; succinate to fumarate plus malate; malate to oxalacetate plus pyruvate; and malate or pyruvate to citrate. Acetate was not metabolized. Succinate oxidation was competitively inhibited by malonate. The significance of these results with regard to the operation of the citric acid cycle in this organism is discussed.
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Studies on a Soap Tolerant Organism: a New Variety of Bacterium anitratum
More LessSummary: A soap-tolerant organism, commonly found in face-flannels and sponges, was compared with Bacterium anitratum, Moraxella Iwoffi var. brevis and Alcaligenes viscosus. These organisms have many characters in common. It is proposed that Bacterium anitratum and related organisms should be included in the family Achromobacteriaceae and that the soap-tolerant organism be considered a new variety of B. anitratum with the provisional name Achromobacter anitratum var. saponiphilum. Some problems of classification of these and similar organisms are discussed.
The soap-tolerant organism had two major antigens; one was associated with the capsule and largely strain specific, the other was common to all strains and was present also in non-capsulated variants. Both antigens were detached from the cell on heating, the specific antigen partially and the common antigen almost completely; they could be demonstrated in the saline medium after suspensions had been heated at 100° for 60 min. and though detached from the cell, could still stimulate antibody formation. There was an antigenic relationship between the soap tolerant organisms and Bacterium anitratum.
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Commensalism in Pathogenic Anaerobic Actinomyces Cultures
More LessSummary: Conversion of a ‘rough’ typical strain of Actinomyces israelii of human origin to a smooth soft form more tolerant of oxygen was found to result from the physical trapping within the mycelium of a few alien and facultatively anaerobic cells. Such cells, which commonly proved to be staphylococci, were isolated in single cell culture by micromanipulative techniques and then grown aerobically. Their presence affected the morphology and oxygen tension requirements of the host. In successfully balanced mixtures the colonies appeared homogeneous anaerobically and failed to grow aerobically. The commensal organism could most readily be detected in a water/gel system in stoppered bottle cultures. Similar associations were obtained from a variety of morbid material, especially that of bovine origin. It is suggested that the descriptions given by various workers at different times of a smooth soft micro-aerophilic organism little given to branching may cover: (1) A. israelii and associates; or (2) a distinct organism earlier described under the name of A. bovis.
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A Partially Defined Culture Medium for Trypanosoma cruzi and some other Haemoflagellates
More LessSummary: A partially defined medium for cultivation of blood flagellates has been developed. In this medium blood was replaced by haematin, crystalline serum albumin and a series of simple growth factors. The medium supported growth of Trypanosoma cruzi, Leishmania tropica, and a few other strains of Trypanosomidae. The growth on this medium was comparable to that obtained on optimal bloodcontaining media; no change in growth was found after prolonged serial subcultivation.
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The Preferential Synthesis of β-Galactosidase in Escherichia coli
More LessSummary: The induced formation of β-galactosidase in relation to overall protein synthesis in Escherichia coli was examined under conditions where the enzyme inducer was required for growth. There was, initially, a substantial production of β-galactosidase without any detectable increase in total cell protein. This phenomenon has been termed ‘preferential’ β-galactosidase synthesis. The occurrence of preferential β-galactosidase synthesis indicates that β-galactosidase formation is a discrete event in cellular metabolism, and is not necessarily geared to overall cell growth. The data obtained also suggest that the carbon source(s) for preferential β-galactosidase synthesis might be of endogenous origin.
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Lampropedia hyalina Schroeter 1886 and Vannielia aggregata n.ǵ., n.sp., with Remarks on Natural and on Organized Colonies in Bacteria
More LessSUMMARY: Two bacteria, Lampropedia hyalina and Vannielia aggregata, are described, which form characteristically shaped aggregations. The differences between artificial, natural and organized colonies are discussed.
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The Morphology and Relationships of ‘Lactobacillus’ bifidus
More LessSUMMARY: Strains of ‘Lactobacillus’ bifidus were found to vary in morphology from large globules to more slender septate rods and filaments, often very profusely branched. Adaptation of anaerobic strains to growth under aerobic conditions is usually accompanied by a diminution in branching. The organism has little or no morphological resemblance to a true Lactobacillus species, but strongly resembles certain strains of Corynebacterium.
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‘Fruity’ and other Mutants of the Cellular Slime Mould, Dictyostelium discoideum: a Study of Developmental Aberrations
More LessSUMMARY: Study of three mutants of Dictyostelium discoideum—Fruity, Bushy and Dwarf—provide specific examples of aberrant behaviour during aggregation and the construction of fruiting bodies. The proportion of initiator cells in the population and the optimal population density for aggregation have been shown to be under genetic control. In the Fruity mutant, the great increase in the number of initiator cells leads to the formation of aggregates composed of very few individuals and correspondingly tiny fruits. The morphology of the aggregates and fruits and the regulatory properties of this morphogenetic system have been examined.
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The Electron-dense Bodies of Mycobacterium phlei
More LessSUMMARY: A method is described in which identical groups of micro-organisms are viewed first in the light microscope and then in the electron microscope. A direct comparison was made between electron micrographs and preparations stained with specific metachromatic, chromatinic and mitochondrial stains. In a study of the electron-opaque granules of the mycobacteria it was shown that they contain metaphosphates and show metachromasia. They are situated between the chromatinic bodies and cannot be identified with mitochondria.
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Cytoloǵical Studies of Nuclear Division in Salmonella typhimurium
More LessSUMMARY: Physiological studies recently led to the development of a technique for obtaining synchronous nuclear division in Salmonella typhimurium. By using this method we have attempted to identify the morphological changes characteristic of nuclear division. The picture obtained is that of a gradual shift from a round nuclear body via ‘wedge’- and ‘bar’- to ‘dumbbell’-like configurations. Mitotic patterns were not observed in these small cells. An indication was obtained that at an early stage of nuclear division the nucleus has already doubled with respect to at least one of its physiological functions. It is discussed to what extent the present studies by selective staining may be used to identify the state of the nucleus as observed by electron microscopy.
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Reconstruction of the Nuclear Sites of Salmonella typhimurium from Electron Microǵraphs of Serial Sections
More LessSUMMARY: A method for obtaining a composite picture of the organisms from electron micrographs of serial sections is described. Evidence is presented that the same general structures are revealed, as far as the nuclear sites are concerned, by selective staining for deoxyribonucleic acid and by electron microscopy of sections.
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The Effects of Metaperiodate and Heated Influenza Virus on Influenza Virus Growth
More LessSUMMARY: Appropriate quantities of sodium metaperiodate injected into hen eggs inhibited the development of full infectivity by some strains of influenza virus, i.e, ‘incomplete’ virus was produced; with other strains of virus the same quantities of metaperiodate inhibited haemagglutinin production. Metaperiodate in a dose which of itself did not inhibit haemagglutinin production by two strains of influenza virus enhanced the inhibitory action of heated influenza virus on haemagglutinin production by these strains. Both sodium metaperiodate and heated influenza virus inhibited the production of influenza virus filaments more than that of spheres. It is suggested that both metaperiodate and heated influenza virus act on a common substrate which is required for the development of both viral agglutinin and full virus infectivity.
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Pigment Production by Staphylococci
More LessSummary: White variants, which were stable over many generations, were isolated from six of eight strains of Staphylococcus aureus by cultivation in fluid medium; their incidence was favoured by 0·5% (w/v) lithium chloride. These variants all resembled the parent culture from which they were derived in the production of free coagulase and α-lysin and, except for one which was non-typable, in bacteriophage type. None of the white variants, however, was clumped by plasma in a slide test, although the parent cultures were.
Golden variants were isolated from two old laboratory strains of coagulase-positive staphylococci which had become white and from three of six white variant cultures isolated in the study of ‘aureus→albus’ variation. These golden variants were isolated under conditions which are unfavourable to the growth of staphylococci in the laboratory. They resembled the parents from which they were derived in production of free coagulase and α-lysin and in bacteriophage type. They differed from the parent cultures in production of the factor which causes clumping in plasma, and showed a non-specific increase in resistance to various antibacterial agents.
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Recombination with Herpes Simplex Virus
More LessSummary: The behaviour of six strains of herpes simplex virus was studied. Marked differences were noted in the type of lesion formed and the rate of attachment when the strains were inoculated on to the chorio-allantois, and in the behaviour of strains inoculated intracerebrally into mice or on to the cornea of the rabbit.
Two easily differentiated strains were inoculated together on to the chorio-allantois under conditions designed to give rise to a proportion of doubly infected cells. After a short period of incubation the progeny of the first intracellular growth cycle was obtained.
Ten clones were isolated, of which six resembled one of the two parents in the type of lesion formed and level of virulence for mice. Of the other four, one (106 a) produced small type lesions and the other three large type. All possessed degrees of virulence intermediate between those of the parents. Three of these substrains showed no alteration in the type of lesions formed or their degrees of virulence after 3 to 5 passages of single lesions at limiting dilution. When the rate of attachment to the chorio-allantois and the behaviour when inoculated on to the cornea of the rabbit were studied, it was found that 106a produced effects intermediate between the parents, whilst the other strains resembled one of the two parents.
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Beta-oxidation of Fatty Acids by Nocardia opaca
More LessSummary: A study of the mechanism of breakdown of ω-phenyl-substituted fatty acids by Nocardia opaca has been made. Acids with an odd number of carbon atoms in the side chain (phenylpropionic, phenylvaleric and phenylheptylic acids) were converted to benzoic acid, and cinnamic acid was an intermediate. o-Hydroxy-phenylacetic acid was identified as a common product when acids with an even number of carbon atoms (phenylacetic, phenylbutyric, phenylcaproic and phenylcaprylic) were used. This evidence supports β-oxidation as a mechanism of breakdown of short chain fatty acids by N. opaca.
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Studies on the Ability of Light to Counteract the Inactivating Action of Ultraviolet Radiation on Plant Viruses
More LessSummary: Of seven plant viruses tested, all except tobacco mosaic showed the phenomenon of photoreactivation, i.e. plants exposed to visible light after inoculation with preparations partially inactivated by ultraviolet radiation produced more local lesions than plants kept in darkness. Five strains of tobacco mosaic virus, which differed widely in their pathogenicity and other properties, were tested, but none showed the phenomenon. Of the six viruses that did, potato showed it much the most strongly, tomato bushy stunt and a tobacco necrosis virus the least; cabbage black ringspot, cucumber mosaic and tobacco ringspot were intermediate.
Photoreactivation does not occur immediately after plants are inoculated. With irradiated preparations of potato virus X, most particles need about 30 min. to reach the state in which their ability to infect is affected by light; once in this state, exposure to daylight for 15 min. gives almost complete photoreactivation. Some irradiated particles respond to light of 80 f.c., but others need brighter light; no additional response occurs when light intensity is increased above 600 f.c. The sensitive state of potato virus X persists for about 1 hr. in plants kept in darkness, after which the particles seem to be permanently inactivated.
With antibodies and enzymes, a constant amount of absorbed energy decreases the activity of a unit weight by a given fraction. This rule does not apply to plant viruses, which lose infectivity with less absorbed energy than the rule predicts. If viruses are more sensitive because they contain nucleic acid, their sensitivity is not a direct function of their content of nucleic acid. Potato virus X has the same nucleic acid content as strains of tobacco mosaic virus, but is inactivated by less absorbed energy and individual strains of tobacco mosaic virus also differ by factors of two in the amount of radiation needed to decrease their infectivity by a given fraction.
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The Action of Fibrinogen on certain Pathogenic Cocci
More LessSummary: The properties of the material responsible for the clumping reaction given by suspensions of coagulase-positive staphylococci when shaken in the presence of fibrinogen were examined and a possible mechanism is suggested for the reaction. Of other bacteria examined only streptococci of groups A, C and G absorbed fibrinogen, and of these relatively few gave clumping, though the cell material responsible for absorption was similar to that found in staphylococci. In staphylococci it is believed that a single substance is responsible for both absorption and clumping, and its properties suggest a peptide complex. The possible usefulness of coagulase-positive cocci in the detection of minute amounts of fibrinogen is indicated.
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The Development of the ‘Straight Rod Type’ of Lactobacillus bifidus
More LessSummary: Microscopical examinations of several Lactobacillus bifidus strains have shown that the ‘bifid’ morphology of the cells, which seems to predominate in vivo, is readily changed on subcultivation in different media in vitro. At first highly branched and larger forms occur, and from these mycelial branched filaments develop. The mycelial cells may swell, in which case intensely staining coccoid granules can be detected in the cells. Ultimately, the filaments break up, and give rise to the development of regular short straight rods. Obviously these straight rods appear from the coccoid granules.
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