- Volume 55, Issue 3, 1969
Volume 55, Issue 3, 1969
- Article
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Conidium Production by Higher Fungi within Thin Layers of Liquid Paraffin: a Slide-culture Technique
More LessSummary: A new slide culture technique is described in which 18 of 34 higher fungi tested sporulated asexually within a thin layer of liquid paraffin, some normally, some more or less abnormally. The oil greatly facilitated observation of the developing structures at high magnifications. The technique promises to be of use in studies of development in higher fungi.
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A Study of the Cell Envelope of the Halobacteria
More LessSUMMARY: Electron microscopy on thin sections of three different extremely halophilic Halobacterium species showed that their cell envelopes were of similar general construction: an inner membrane and an outer layer. The outer layer stains most strongly in the outermost part. When the NaCl concentration of the environment was lowered from the optimal of 4·3 m to 2·2 m the outer layer of the cell envelope of Halobacterium salinarium strain 1 became frayed; in many cells a release of material from the outer layer appeared to take place. When the cells were exposed to distilled water the outer layer of the envelope appeared to dissolve completely and the cell membrane disintegrated into tiny flakes. Fragments of the cell envelope produced by mechanical disintegration of the cells in 4·3 m-NaCl formed closed vesicles very rapidly; some of the cytoplasmic material became trapped inside the vesicles. Detergents appeared to slow down the closing of the vesicles and also to cause a release of material from the outer layer of the cell envelope. The cell envelope vesicles were mainly composed of protein and lipid; their content of amino sugar was low compared with the cell envelope of other Gram-negative bacteria. The cell envelope vesicle also contained nucleic acids; most of these were probably parts of the cytoplasmic material trapped inside the vesicles. The amino acid composition showed that the protein of the cell envelope vesicles was quite acidic, consistent with the contention that high concentrations of sodium ions stabilize the cell envelopes of these organisms by neutralizing the negative charges of the protein. Upon centrifugation at high speed of the lysate obtained by dialysis of the cell envelope vesicles against distilled water, the fragments of the cell membrane sedimented whereas most of the protein, presumably from the outer layer of the cell envelope, stayed in the supernatant fraction. Carotenoids and cytochromes were contained in the sediment with the membrane fragments. Most of the amino sugar-containing components stayed in the supernatant fraction; in the presence of 10–25 m salt most of the amino sugar-containing components sediment with the membrane fragments.
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Growth and Pigmentation of Micrococcus Radiodurans
More LessSUMMARY: Micrococcus radiodurans grew well between 25° and 40° with an optimum at 25° to 30°. At 35° pigmentation lagged behind growth after 3 days, growth and pigmentation showed similar maxima at 25°. The bacterium appeared to synthesize five carotenoids, at least two of which have the same chromophore and are keto-carotenoids.
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An Evaluation of the Pathways of Metabolism of Glucose, Gluconate and 2-Oxogluconate by Pseudomonas Aeruginosa by Measurement of Molar Growth Yields
More LessSUMMARY Pseudomonas aeruginosa, atcc 9027, was grown in a simple ammonium salts medium with limiting glucose, gluconate or 2-oxogluconate as the sole carbon and energy source. There was little difference in molar growth yield between glucose and gluconate but with 2-oxogluconate the yield was signi-cantly less. Measurement of Y o2 values (g. dry weight of cells produced/mole of oxygen consumed) during growth on the three substrates indicated most efficient oxygen utilization with 2-oxogluconate. The results are discussed in relation to the relative metabolic importance of the various pathways of of glucose metabolism in the organism.
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The Coupling of Phosphate Accumulation to Acid Production by a Non-growing Streptococcus
More LessSUMMARY: Accumulation of phosphate by washed, stored suspensions of stationary phase streptococcal strain sl-i is strictly energy-dependent, essentially unidirectional and coupled stoichiometrically to acid production. At saturating concentrations of extracellular glucose and phosphate, incubation at varying pH values alters the rates of phosphate accumulation and concomitant fermentation of glucose such that coupling remains intact. Extracellular pH, while not affecting the coupling of phosphate accumulation to acid production, determines the total capacity for accumulation of phosphate and consequently the point of uncoupling of these processes. The conditions of cell storage profoundly affect the pH dependency of phosphate accummulation. During phosphate accumulation, the intracellular o-PO4 pool contracts by more than 50 %. About half of the accumulated phosphate appears in a high molecular weight fraction (i.e. insoluble in cold HClO4) under conditions which contraindicate net nucleic acid synthesis, protein synthesis or the incorporation of exogenous glucose carbon into high molecular weight cell constituents. The data are consistent with the hypothesis that stationary phase streptococcus sl-i synthesizes inorganic polyphosphates.
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Regulation of Gratuitous β-Galactosidase Synthesis in Aerobacter Aerogenes during an Adaptive Process
More LessSUMMARY: When cells of Aerobacter aerogenes, growing exponentially in either glucose+mineral salts medium, or lactose+mineral salts (being fully adapted to growth in lactose), are inoculated for the first time into maltose+mineral salts medium containing 10−3 m-methyl-β- d- thiogalactoside, a very large amount of β-galactosidase is synthesized gratuitously during the lag and early stages of growth in the new medium. The abnormally high enzyme levels are maintained for some time. This is a form of ‘preferential synthesis’, which can be ascribed to a failure of catabolite repression during exposure to an unfamiliar compound as source of carbon and energy. The extent of preferential synthesis is increased by starvation of the organisms prior to inoculation in maltose medium.
Similar experiments involving organisms partially or completely adapted to growth in maltose show a smaller degree, or complete absence, of preferential synthesis and enhanced enzyme levels. The efficiency with which maltose exerts the ‘catabolite repression’ effect is thus a function of the degree of adaptation of the organisms to maltose as sole carbon source.
It is suggested that this breakdown of catabolite repression, followed by its recovery during adaptation, could well be a useful general feature of the adaptive process.
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The Incomplete Tricarboxylic Acid Cycle in the Blue-green Alga Anabaena Variabilis
More LessSummary: The presence of an incomplete tricarboxylic acid cycle in Anabaena varia-bilis and Anacystis nidulam is described. These blue-green algae lack both α-oxoglutarate dehydrogenase and succinyl-CoA synthetase. Succinyl-CoA was formed in extracts of A. variabilis by 3-ketoacyl CoA-transferase using acetoacetyl-CoA as CoA donor. The activities of the other tricarboxylic cycle enzymes were measured in extracts prepared from autotrophic organisms and from those grown in the presence of acetate. No alterations in activity indicative of enzyme repression or de-repression were observed. These results are discussed in relation to possible reasons for autotrophic behaviour.
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Studies on Negative Chemotaxis and the Survival Value of Motility in Pseudomonas Fluorescens
More LessSUMMARY: Multiplication of aerobic piliated fla+ and fla− Pseudomonas fluorescens growing in aerated mixed culture gave fla+:fla− ratios approximately 1:1 over a 24 hr growth period. When fla+ and fla− were cultured simultaneously in non-aerated media, fla+ then outgrew the fla− mutant to a final (24 hr) ratio of 10:1 or greater, thereby lending supporting evidence to the view that motility is a survival factor in environments where ‘nutrients’ are limited or discontinuous.
Gravity, magnetism, and light did not influence a negative chemotactic response of fla+ P. fluorescens to hydrogen ions. Temperature variations, pH, or viscosity alterations either inhibited or stimulated motility, thereby making impossible a determination of their specific effects. Various antibiotics, membrane-active agents, and protein or DNA synthesis inhibitors were employed in attempts to interfere with the chemotactic response, but none completely inhibited chemotaxis without also affecting motility. The cytoplasmic membrane may act as a transducer of environmental stimuli in chemotaxis.
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The Formation of Buds in Yeast
More LessVesicles accumulate at the site of bud formation in the mother cell and are also found in the growing bud during the growth of its wall. The bud is in direct communication with the mother cell until maturity when a septum which is formed across the cytoplasm grows inwards from the wall and is subsequently thickened on both sides. During the thickening process vesicles are present at both surfaces of the cross-wall which finally has two layers one of which becomes continuous with the bud cell wall. It is suggested that the vesicles carry material both into the growing bud wall and into the septum.
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Characterization of Leptospires according to Fatty Acid Requirements
More LessSUMMARY: The fatty acid requirements of leptospires parasitic for mammals were compared to those of members of the ‘biflexa complex’ (leptospires not clearly demonstrated to be animal parasites). The parasitic leptospires grew on unsaturated fatty acids. Saturated fatty acids were not utilized unless an unsaturated fatty acid was also provided. This requirement for an unsaturated fatty acid was increased at temperatures above and below the optimal. In addition, these leptospires did not utilize fatty acids containing less than 15 to 16 carbon atoms unless a longer chain fatty acid was also present. Leptospires of the ‘biflexa complex’ had neither of these requirements. These leptospires grew on either long or short chain, saturated or unsaturated fatty acids. Utilizing these differences in fatty acid requirements, a means of differentiating these two groups of leptospires is provided. Members of the ‘biflexa complex’ but not the parasitic leptospires grew on an albumin medium containing 5 × 10−4 m-myristic acid, the 14-carbon saturated fatty acid.
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Lysogenic Mycobacteria: Phage Variations and Changes in Host Cells
More LessSUMMARY: Lysogenic conversion of mycobacteria by phage Roy results in reciprocal changes in the phase and in the host cells. The temperate phage released after lysogenization differs from the converting phage in its host range. The lysogenic derivatives show marked changes in their colony morphology and in their sensitivity to phagolysis. Some, but not all, of the lysogenic bacteria have suffered losses in enzymic activity. An attempt is made to distinguish between host-determined and phage-determined variations.
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Proteins Immunologically Related to Neurospora Histidinol Dehydrogenase
More LessSUMMARY: Antibody to pure Neurospora histidinol dehydrogenase has been prepared from rabbits. Extracts of Neurospora strains mutant at the his-3 locus have been examined by the double diffusion technique to ascertain whether or not they produce proteins which cross-react with this antibody. A total of 129 mutants, including 52 non-complementing ones, gave a positive reaction; no mutants have yet been observed which gave a negative result. In all cases two major precipitin bands were produced and it was shown that these corresponded to the 4S and the 7S forms of the enzyme. Dehydrogenation of histidinol by purified wild-type enzyme was completely inhibited by the antibody prepared against pure histidinol dehydrogenase and by antibody prepared against pure HD from the mutants k445 and k959, which produce a modified HD enzyme. HD activity was also inhibited by antibody prepared against partially purified homologous protein from the two noncomplementing mutants k492 and k474. It was possible to reduce the efficiency of neutralisation of HD by antibody if this was treated with extracts of mutants k492 and k474.
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Spore Concentrations in the Atmosphere at Ahmadi, a New Town in Kuwait
More LessSUMMARY: The fungal air spora and the microfungi in house dust are described. Pollens from indigenous weeds of the Chenopodiaceae which were deliberately planted in the area were most numerous, that from the introduced trees of Prosopis spicigera (an important allergen) was trapped only sporadically at roof-top level, but found in high concentration beneath the trees. Low Cladosporium counts in the hot season are related to degree-days above 29°. The origins of the spora and the possibility of dust being colonized by fungi in air-cooled houses is discussed. Since inhalant allergy is likely to increase among the population as planting programmes extend the areas of vegetative cover in this hot arid region, future surveys on the air spora are desirable.
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Characterization of Human Cutaneous Lipophilic Diphtheroids
More LessSUMMARY: Sixty lipophilic diphtheroids (LD) isolated from human skin were characterized by a variety of morphological, biochemical, physiological and nutritional tests. The LD strains were tentatively placed into six fermentative groups and one non-fermentative group. Most LD strains required amino nitrogen, others required vitamins plus amino acids for growth. Nine LD isolates initiated growth with ammonia as a sole nitrogen source. Urea and nitrate were not utilized. A total of 149 cutaneous bacteria were compared for esterase and lipase action. Esterase activity was common but few LD strains appear capable of obtaining their required lipids by their own lipase action. The grouping scheme derived from studies with the 60 LD strains was tested as a screening procedure to recognize and categorize other LD strains. A second series of 115 cultures from seven cutaneous sites were isolated. Six of the original seven groups were identified and one additional subgroup was formed. The screening method was partially effective as a means of studying the location and types of LD strains on skin. There were 31 strains which by determinative features could be grouped as Corynebac- terium xerosis- like species. Human skin appears to have an unrecognized diversity of lipophilic corynebacteria yet to be classified into species.
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Cellulolytic Bacteria Occurring in the Rumen of Sheep Conditioned to Low-protein Teff Hay
More LessSUMMARY: From a large number of cultures of cellulolytic bacteria isolated from rumen contents of sheep conditioned to low-protein teff hay through the use of both a selective medium containing finely ground cellulose as energy source and a less selective medium containing cellobiose, xylan and starch, thirty isolates, representing three morphological types, were selected for detailed characterization. Nineteen isolates of Gram-negative curved rods belonged to the genus Butyrivibrio. Of these one was identical with and ten closely related to B. fibrisolvens. The remaining eight Butyrivibrio cultures differed in several respects from the only other defined species within this genus, B. alactacidi-gens. Four coccal isolates were identified as Ruminococcus albus and five as R.flavefaciens. Two strains of sporeformers belonged to the genus Clostridium but could not be identified with any of the cellulolytic species of this genus listed by Bergey’s Manual.
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Extent of Solubilization of α-Cellulose and Hemicellulose of Low-protein Teff Hay by Pure Cultures of Cellulolytic Rumen Bacteria
S. G. Kock and A. KistnerSUMMARY Ten isolates belonging to the genus Butyri vibrio and two each of Rumino-coccusalbus, R. flavefaciens and an unidentified Clostridium sp. were isolated from high dilutions of rumen fluid from sheep conditioned to low-protein teff hay. The butyrivibrios solubilized between io and 37 % of the α-cellulose of the hay (average 21 %). The two isolates of Ritminococcus albus degraded 43 and 56 % of the α-cellulose and the two of R. flavefaciens 39 and 66 %, while the two Clostridium cultures achieved only 10 % degradation. Hemicellulose degradation by the Butyrivibrio isolates was between 25 and 67 % (mean 48 %) and that by the four Ruminococcus cultures between 47 and 65 %. One of the Clostridium cultures solubilized 21 % and the other 51 % of die hemicellulose. The butyrivibrios appear capable of contributing a greater share towards cellulose digestion in ruminants on low-protein hay than has been inferred from qualitative in vitro tests for cellulolysis, using refined cellulose preparations; they are probably less active than the ruminococci.
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