bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation de l'efficacité de la technique d'adsorption-élution du poliovirus 1 sur filtres en fibres de verre: application à l'analyse virologique de 100 ml à 1000 ℓ d'eau
Authors: Payment Pierre , Trudel Michel , Pavilanis Vytautas
Published: April 2010

The efficiency of the adsorption-elution technique using fiber glass filters to concentrate viruses from water was evaluated to detect poliovirus type 1 in drinking, river, and sewage water. At pH 3.5 and with 5 × 10−4 M aluminium chloride more than 99% were adsorbed to a 0.25-μm filter. Beef extract (3%), pH 9, eluted 85–95% of the adsorbed viruses and organic flocculation at pH 3.5 permitted to reconcentrate the viruses in 1/20of the elution volume with a 50–72% efficiency. The overall efficiency of the technique for 100 ml to 1000 ℓ of the different types of water using 102 to 106 PFU was 38 to 58%.
Osmotic effects on radial growth rate and specific growth rate of three soil fungi
Authors: Sterne R. E. , McCarver T. H.
Published: April 2010

The radial growth rate on osmotically adjusted agar medium and the relative specific growth rate in osmotically adjusted liquid medium were determined for Rhizoctonia solani, Pythium ultimum, and Verticillium dahliae. On basal medium, an isolate of P. ultimum and R. solani had similar radial growth rates of 0.52 and 0.47 mm/h, respectively, whereas V. dahliae grew at a rate of 0.08 mm/h. Radial growth rate was reduced 50% at osmotic potentials of −16, −27, and −32 bars for P. ultimum, R. solani, and V. dahliae, respectively. No growth occurred at −32 bars for P. ultimum, −56.2 bars for R. solani, and −100 bars for V. dahlia. Specific growth rates in liquid culture were 0.011 h−1 for P. ultimum, 0.008 h−1 for V. dahliae, and 0.026 h−1 for R. solani. Ratios of radial growth rate (Kr) to specific growth rate (αs) were computed for each fungus growing at different osmotic potentials. There was not a constant relationship between Kr on agar and αs in liquid medium, e.g., Kr/αs ratios varied from 8–41% from a mean ratio for a particular species. The results indicated that radial growth rate on osmotic agar was not useful as a measure of relative specific growth rate of a fungus in osmotically adjusted liquid medium.
Organ distribution and viability of Candida albicans in noncancerous and tumor-bearing (Lewis lung carcinoma) mice
Authors: Mardon D. N. , Robinette Jr. E. H.
Published: April 2010

Lethality due to infection with Candida albicans is significantly delayed in mice bearing the transplanted Lewis lung carcinoma. When the distribution and growth of this microorganism in reticuloendothelial cell-rich organs was examined using live radioactive (14C) Candida cells and viable Candida colony-forming units as criteria for measurement, the following relationships were found. A smaller percentage of the C. albicans inoculum localized in the liver of tumor-bearing mice in comparison with noncancerous control mice, while a more rapid rate of Candida inactivation occurred in the liver of mice bearing the Lewis lung carcinoma than in control animals. Patterns qualitatively similar to, but quantitatively less pronounced than those seen with the liver were observed when the spleen and lungs of noncancerous and tumor-bearing mice were compared. In both groups of animals the kidneys were the only sites where detectable multiplication of the microorganism took place, and the rate of Candida growth was more rapid in the kidneys of control animals than in cancerous mice. Our results indicate that in mice bearing the Lewis lung carcinoma, decreased hepatic localization and increased killing of C. albicans occurs, and that these effects may reflect enhanced microbial destruction in fixed reticuloendothelial cells.
Reversal of succinate-mediated catabolite repression of alkylsulfatase in Pseudomonas aeruginosa by 2,4-dinitrophenol and by sodium malonate
Authors: Fitzgerald J. W. , Kight-Olliff L. C. , Stewart G. J. , Beauchamp N. F.
Published: April 2010

The Kreb's cycle intermediates and related metabolites (e.g., acetate) repressed the induced synthesis of alkylsulfatase in resting cell suspensions of Pseudomonas aeruginosa. At concentrations which caused substantial repression, sodium succinate as well as sodium malate, fumarate, and α-ketoglutarate were oxidized to yield consistently high levels of ATP throughout the induction period. Sodium oxalacetate which was markedly less effective as a metabolite repressor generated high ATP levels only during the first 2 h of the induction period. The addition of 2,4-dinitrophenol or sodium malonate to cell suspensions containing the inducer (sodium hexan-1-yl sulfate) and succinate overcame repression of alkylsulfatase formation and resulted in a reduction in the ATP content to levels found in cells exposed only to inducer. An apparent stimulation of alkylsulfatase induction occurred in the absence of succinate when cells were incubated with 2,4-dinitrophenol and inducer. In this case, the ATP content of the cell suspension fell to levels substantially below those occurring as a result of inducer catabolism. Collectively, these data suggest that the effectiveness of succinate as a metabolite repressor is related to the ATP levels generated as a consequence of succinate oxidation.
Mode of action of bacteriophage &phi149 on cholera and E1 Tor vibrios
Authors: Maiti M.
Published: April 2010

Bacteriophage [Formula: see text] which was propagated in Vibrio cholerae (classical) OGAWA 154 strain, killed Vibrio cholerae (E1 Tor) strain MAK 757 without phage propagation. E1 Tor vibrios underwent a small degree of lysis only when infected by the phage [Formula: see text] at a high multiplicity of infection and lost their viability at a rate-dependent multiplicity of phage infection. Evidence was obtained with 32P-labelled bacteriophage [Formula: see text] for penetration of phage DNA into both bacterial strains. In host strain (OGAWA 154) phage particle synthesis occurred normally. In E1 Tor strain MAK 757 the phage DNA was not degraded but its expression was blocked. The killing effect of ([Formula: see text] on E1 Tor strain MAK 757 is supposed to be due to damage of the cytoplasmic membrane, which could not be repaired under the influence of phage information. This was indicated by a blockage of cellular respiration and RNA and protein synthesis.
Studies of the microaerophilic nature of Campylobacter fetus subsp. jejuni. II. Role of exogenous superoxide anions and hydrogen peroxide
Authors: Hoffman Paul S. , George Hugh A. , Krieg Noel R. , Smibert Robert M.
Published: April 2010

The addition of bovine superoxide dismutase to Brucella broth or Brucellar agar greatly enhanced the oxygen tolerance of Campylobacter fetus subsp. jejuni strain H840 (ATCC 29428). Catalase also enhanced oxygen tolerance, but to a lesser extent. These enzymes must act externally to the bacteria. All of the diverse compounds which enhance oxygen tolerance of C. fetus, including nor-epinephrine and a combination of ferrous sulfate, sodium metabisulfite, and sodium pyruvate, share the ability to quench either superoxide anions or hydrogen peroxide. On the basis of these and other data, we propose that C. fetus is more sensitive to exogenous superoxide anions and hydrogen peroxide than are aerotolerant bacteria, despite the occurrence of superoxide dismutase and catalase activities in C. fetus. Compounds that enhance oxygen tolerance in C. fetus appear to act by quenching superoxide anions and hydrogen peroxide which occur spontaneously in the culture medium.
Mycoparasitism of sclerotia of Sclerotinia and Sclerotium species by Sporidesmium sclerotivorum
Authors: Ayers W. A. , Adams P. B.
Published: April 2010

Sclerotia of Sclerotinia sclerotiorum in soil were invaded by a destructive fungus that was isolated and identified as Sporidesmium sclerotivorum. The parasitic fungus grew slowly on an autoclaved agar medium made from comminuted sclerotia of S. sclerotiorum and on cornmeal agar but failed to germinate or grow on many common mycological media. Macroconidia of S. sclerotivorum germinated adjacent to sclerotia on water agar or moist filter paper, colonized the sclerotia, and developed two distinctive asexual spore states by which it could be recognized. In moist sand, steamed soil, and natural soil the mycoparasite infected and destroyed more than 95% of the amended (1% w/w) sclerotia of S. sclerotiorum in 10 weeks or less at 25 °C. Sclerotia killed by autoclaving were poorly colonized. Sclerotia of Sclerotium cepivorum were attacked by the mycoparasite more slowly than those of S. sclerotiorum. Sclerotia of Macrophomina phaseolina apparently were not parasitized. The mycoparasite was isolated from soils from three different areas of the northeastern United States. The prolific development of the mycoparasite in soil containing sclerotia of susceptible species and its ability to spread through soil by growth from one sclerotium to another suggest that S. sclerotivorum is an important contributor to the natural destruction of sclerotia in.soil and that it may have high potential as an applied agent of biological control of sclerotial fungi.
The physiological effects of restrictive environmental conditions on Dictyostelium discoideum spore germination
Authors: Cotter David A. , Garnish Frederick J. , Tisa Louis S.
Published: April 2010

Spores may be reversibly activated by the application of heat, dimethyl sulfoxide, urea, or ethylene glucol. Severe changes in four environmental variables (high osmotic pressure, low oxygen tension, low or high pH, and low or high temperature) interfere with the germination process. Spores at the end of the postactivation lag phase of germination were usually deactivated if exposed to severe environmental conditions and thus did not swell; spores in the swelling and emergence stages of germination were killed if exposed to severe environmental conditions. The oxygen uptake which began during spore activation was primarily attributable to a cyanide-sensitive pathway and secondarily to a salicylhydroxamic acid (SHAM) sensitive pathway. Inhibition of the SHAM-sensitive pathway did not cause spore deactivation while the addition of cyanide resulted in rapid spore deactivation. Treatment of activated spores with azide or environmental shifts also resulted in inhibition of oxygen uptake and spore deactivation. Deactivating spores did not demonstrate the amino acid incorporation, uridine incorporation, and expression of trehalase activity which is found in the later stages of germinating control spores. Protein synthesis inhibitors did not cause spore deactivation or a decrease in oxygen uptake but they inhibited amino acid incorporation and the expression of trehalase activity in swollen spores. It is concluded that control of respiratory activity is involved in regulation of reversible activation.
Regulation of extracellular protease formation by Serratia marcescens
Authors: Bromke Bruno J. , Hammel Jay M.
Published: April 2010

Heavy cell suspensions of Serratia marcescens, when grown in gelatin-containing media, produce extracellular proteases which increase in specific activity in a linear fashion for 3 to 4 h. During partial purification, a single peak of proteolytic activity was demonstrated by Sephadex G-100 chromatography. However, electrophoresis using 5% polyacrylamide gels discloses three proteolytically active bands. Evidence in favor of gelatin acting as an inducer of the 'proteolytic system' was provided by two observations. First, proteolytic activity is only present in media containing gelatin. Secondly, the addition of 10−4 M rifampicin to cells growing in gelatin-containing medium plus an additional carbon source inhibits protease activity totally, but has no effect on growth. When glycerol is added to a growing cell suspension in gelatin-containing medium, growth increases, but protease specific activity decreases. This 'glycerol effect' is not due to an accumulation of active or inactive enzyme in association with the cell, nor to a decrease in the total number of proteases synthesized. Rather, glycerol, as other utilizable carbohydrates, exerts a repression which can be eliminated by 5 mM dibutyryl cyclic AMP.
Fatty acid composition of Rhizobium spp.
Authors: MacKenzie S. L. , Lapp M. S. , Child J. J.
Published: April 2010

The fatty acid composition of 42 isolates belonging to the major plant affinity groups of Rhizobium has been determined and found to vary reproducibly with culture age. Numerical taxonomic techniques applied to the 15 major fatty acid components of log-phase cultures of comparable physiological age showed that the rhizobia constitute a uniform group. However, two clusters comprising soybean–cowpea isolates and pea–bean isolates were evident. These observations, based on a simple analysis of only one group of chemical components, indicate relation ships among rhizobia which differ from the conventional plant-affinity groupings but which are consistent with other proposed relationships established using a variety of biochemical and physiological criteria.
Bacteriophage–like particles associated with a spirochete
Authors: Berthiaume L. , Elazhary Y. , Alain R. , Ackermann H.-W.
Published: April 2010

A lysed Treponema bacterium containing cubic phage-like particles, approximately 40 nm in diameter, has been observed by negative staining electron microscopy.
Effect of irradiance upon the population of Pseudomonas coronafaciens in leaves and symptom expression of halo blight of rye
Authors: Cunfer Barry M. , Youmans John
Published: April 2010

The toxin-induced chlorosis caused by Pseudomonas coronafaciens is influenced by irradiance. Three levels of irradiance caused differences in symptom expression but did not affect the rate of increase or final population of viable cells of P. coronafaciens in rye leaves. Distinct and faint halo blight symptoms appeared in 3–4 days in full light (1425 μ W cm−2), and 58% shade (598 μ W cm−2) respectively. No symptoms or only faint symptoms appeared after 7 days at 86% shade (202 μ W cm−2). When plants kept in 58 and 86% shade were moved to full light 5 days after inoculation, lesion size and chlorosis increased rapidly during the next 2 days. On the 7th day after inoculation, the size of lesions from the 58 and 86% shade treatments exceeded those in full light by 2.5 and 5 times, respectively. A chlorosis index based on lesion size and chlorophyll loss within lesions also reflected this trend although chlorophyll loss was greater in lesions in full light for 7 days. Conditions of low irradiance such as that caused by overcast weather and (or) a dense leaf canopy followed by bright sunshine can cause greater losses from halo blight than a continuous period of high irradiance. Sympton expression may be masked by low irradiance but increase of inoculum is not impaired. Although increased light enhances chlorosis, toxin diffusion or production may be reduced.
The production of chaetoglobosins, sterigmatocystin, O-methylsterigmatocystin, and chaetocin by Chaetomium spp. and related fungi
Authors: Udagawa S. , Muroi T. , Kurata H. , Sekita S. , Yoshihira K. , Natori S. , Umeda M.
Published: April 2010

Production of mycotoxins by Chaetomium spp. and related fungi on rice culture was examined by a combination of cytotoxicity tests using HeLa cells and thin-layer chromatography. Three species, C. mollipilium, C. rectum, and C. subuffine, as well as C. cochliodes and C. globosum, were proved to produce chaetoglobosins. From cultures of four strains of Chaetomium sp., assigned to C. thielavioideum, and one strain of Farrowia sp., chaetocin, sterigmatocystin, and O-methylsterigmatocystin were isolated. Morphological characteristics of the producers of sterigmatocystins are described.
Characterization of an enzyme from Rhizoctonia praticola which polymerizes phenolic compounds
Authors: Bollag Jean-Marc , Sjoblad Roy D. , Liu Shu-Yen
Published: April 2010

An extracellular phenol oxidase from the fungus Rhizoctonia praticola which polymerizes various xenobiotic phenols was isolated and characterized. The enzyme was purified by DEAE-cellulose and Sephadex G-200 chromatography followed by preparative polyacrylamide gel electrophoresis. Atomic absorption and EPR spectroscopy indicated the presence of copper, and SDS gel electrophoresis revealed a molecular weight of 78 000. With 2,6-dimethoxyphenol as substrate, the enzyme showed a pH optimum of 6.7–6.9, and a temperature optimum of 40 °C. According to these and additional characteristics it appears that the enzyme belongs to the class of laccases.
Inhibitory effect of cocoa powder on the growth of a variety of bacteria in different media
Authors: Park C. E. , Stankiewicz Z. K. , Rayman M. K. , Hauschild A. H. W.
Published: April 2010

The inhibitory effect of cocoa powderon 102 organisms belonging to 13 genera was determined. All organisms tested were inhibited by 5% cocoa. Shigella, Staphylococcus, Micrococcus, and Bacillus were the most sensitive. The degree of inhibition depended on the organism, temperature of incubation, and the medium in which the cocoa powder was suspended. Of six media tested, lactose broth and nutrient broth were the most inhibitory, while non-fat dry milk was the least inhibitory. Supplementing NB with tryptone or casein reduced the toxicity of cocoa.
The influence of cations on the permeability of the outer membrane of Salmonella typhimurium and other gram-negative bacteria
Authors: Stan-Lotter H. , Gupta M. , Sanderson K. E.
Published: April 2010

The high sensitivity of rough mutants of Salmonella typhimurium, S. minnesota, and Escherichia coli 08 (i.e. with defects in the carbohydrate core of the lipopolysaccharide) to several antibiotics and to the dye gentian violet could be substantially reduced by the addition of cations (Mg2+, Na+) into the growth medium. One heptoseless mutant of S. typhimurium (chemotype Re) and its isogenic smooth parent strain were studied in more detail. The uptake of gentian violet was about 20% in the smooth strain, about 60% in the Re strain grown without additional cations, but decreased to about 15% in the same strain, when cations had been present during growth. In all cases, almost 50% of the gentian violet taken up by the cells was membrane-bound. The total membranes of the Re strain grown in nutrient broth without additional Mg2+ ions were reduced in the 36K and 34K major outer membrane proteins compared with the smooth strain; when grown with added cations the Re total membranes (and even whole cells) did not revert to the protein pattern of the smooth strain.
Nutrition carbonée et étude taxonomique de Bacillus subtilis et B. licheniformis
Authors: Durand M. , Pichinoty F. , Job C. , Mandel M.
Published: April 2010

All 14 strains of B. subtilis can use the following 17 sources of carbon and energy: D-glucose, D-mannose, D-glucosamine, salicin, D-ribose, maltose, sucrose, cellobiose, trehalose, arbutin, starch, mannitol, glycerol, glycerate, pyruvate, fumarate, and L-proline. All 15 strains of B. licheniformis can use the following 41 sources of carbon and energy: D-glucose, D-galactose, D-mannose, D-fructose, D-glucosamine, α-methyl-D-glucoside, β-methyl-D-glucoside, salicin, D-gluconate, saccharate. D-xylose, L-arabinose, L-rhamnose, D-ribose, maltose, sucrose, cellobiose, melibiose, trehalose, arbutin, raffinose, starch, inulin, mannitol, D-sorbitol, glycerol, glycerate, citrate, L-malate, D-malate, mucate, pyruvate, fumarate. α-L-alanine, α-D-alanine, asparagine, L-glutamate, L-arginine, DL-ornithine, L-proline, and 4-amino-n-butyrate. The 29 strains form two distinct groups. Group A includes the 15 strains of B. licheniformis and 2 strains of B. subtilis; group B is formed of 11 strains of B. subtilis; the remaining strain of B. subtilis belongs to neither group. Bacillus licheniformis is a more homogeneous species than B. subtilis. The percentage of guanine + cytosine in the DNA of all 29 strains was determined. In the 14 strains of B. subtilis the average is 46.3% ± 1.5. In the 15 strains of B. licheniformis the average is 46.4% ± 0.9.
Thiosulfate formation and associated isotope effects during sulfite reduction by Clostridium pasteurianum
Authors: Chambers L. A. , Trudinger P. A.
Published: April 2010

During growth of Clostridium pasteurianum on sulfite, approximately half the sulfite was reduced to sulfide and half to thiosulfate. Sulfide was enriched in 32S or 34S at different stages of growth and thiosulfate was enriched in 32S, particularly in the sulfane atom.It is suggested that thiosulfate in these bacterial cultures arose from a secondary chemical reaction. The chemical formation of thiosulfate from sulfide and sulfite was also accompanied by sulfur isotope fractionation. The implications of these results with respect to 'inverse' isotopic effects are discussed.
Spheroplasts of Methanospirillum hungatii formed upon treatment with dithiothreitol
Authors: Sprott G. D. , Colvin J. R. , McKellar R. C.
Published: April 2010

Strains of Methanospirillum hungatii, when treated with dithiothreitol at alkaline pH, formed spheroplasts which lysed in the absence of an osmotic stabilizer. Other methanogenic bacteria showed no response to this treatment, including Methanobacterium thermoautotrophicum. Methanobacterium strain M.o.H., Methanobacterium strain G2R, and Methanosarcina barkeri. The reaction with M. hungatii proceeded slowly at pH 8.0, but increased dramatically up to a pH of 10. Spheroplasts did not form in the presence of MgCl2 or if large amounts of FeS precipitate had been deposited on the cells during growth. Ultra-thin sections of M. hungatii GPI confirmed that individual cells, surrounded by a membrane and an inner wall, were contained within an outer wall or sheath. Adhesive material, which stained in the region of the cell spacer, was observed to bind together the inner and outer wall layers. After treatment with dithiothreitol, the spheroplasts, which retained the flexible inner wall and membrane, were released from the rigid outer wall. Examination of the isolated outer cell wall revealed that dithiothreitol (and dodecyl sodium sulfate) dissolved the adhesive material and damaged the cell spacer at the attachment site to the outer wall. It is proposed that dithiothreitol at alkaline pH loosens both the cell spacer and inner wall attachments to the outer wall, thereby allowing the osmotic pressure of the cytoplasm to eject the spheroplast. Resistance of the cells to lysis by Triton X-100 is lost upon spheroplast formation, indicating that protection to the cell is conferred by the outer cell wall.
Evidence of a competitive hierarchy among coprophilous fungal populations
Authors: Wicklow Donald T. , Hirschfield B. J.
Published: April 2010

Evidence is presented that interference competition may be important in later stages of fungal colonization of cattle feces from a semiarid grassland in Colorado. Cultural antagonism was examined among fungal isolates representing early sporulating colonists (Ascobolus furfuraceus and Saccobolus truncatus), later sporulating colonists (Iodophanus carneus, Coniochaeta discospora, Hypocopra merdaria, and Poronia punctata), and one early successional species that is able to persist (sporulate) through later stages (Podospora decipiens). Poronia punctata, a comparatively slower-growing and later-appearing colonist (18- to 54-month-old fecal pats), is uniformly antagonistic to all of seven earlier-appearing and co-occurring fungal species. Antibiosis is believed to account for the observed antagonism. The authors suggest that the evolutionary product of interference competition among coprophilous fungal populations may be a pattern of competitive hierarchy in which certain slower-growing, later-successional species can limit the reproductive potential of other fungal colonists on fecal substrates.
Patulin biosynthesis: the metabolism of phyllostine and isoepoxydon by cell-free preparations from Pencillium urticae
Authors: Sekiguchi Junichi , Gaucher G. Maurice
Published: April 2010

Cell-free extracts of Penicillium urticae (NRRL 2159A), and its Par− mutants, J2, J1, and S11, were found to contain significant NADP-dependent isoepoxydon dehydrogenase activity. This reversible interconversion of the epoxides (−)-phyllostine and (+)-isoepoxydon occurred optimally at pH5.8 and was completely inhibited by 1 mM p-chloromercuribenzoate (PCMB). The cytosol enzyme possessed specificity for both substrate and cofactor since neither (+)-epoxydon, an epimer of (+)-isoepoxydon, nor NADH was utilized. Cell extracts of the parent and of mutant J2, which is blocked before the epoxides in the patulin pathway, were found to convert phyllostine and isoepoxydon to a number of unknown metabolites which appeared as yellow spots on thin-layer chromatograms after spraying with a chromogenic reagent. Extracts of mutant J1 were unable to carry out this conversion, while whole cells of mutant S11 accumulated what appeared to be these same 'yellow' compounds. Since PCMB-treated extracts of J2 converted phyllostine but not isoepoxydon to these new metabolites, phyllostine appeared to be their more immediate precursor. The relative positions of isoepoxydon and phyllostine in the patulin pathway are discussed.
Changes in electrophoretic mobility and lytic enzyme activity associated with development of flocculating ability in Saccharomyces cerevisiae
Authors: Beavan M. J. , Belk Diane M. , Stewart G. G. , Rose A. H.
Published: April 2010

Cells from stationary-phase cultures of two strains of Saccharomyces cerevisiae (3 and 20) failed to flocculate when grown in a complex or a chemically defined medium, while those of two other strains (11 and 13) flocculated when grown in either medium. Strain 30 flocculated when grown in complex but not defined medium and harvested from stationary-phase cultures. pH – electrophoretic mobility measurements on all five strains showed that mobility attributable to carboxyl groups usually increased as cultures progressed from the exponential to the stationary phase, while that caused by phosphate groups tended to decline. Acquisition of flocculating ability was accompanied in strains 11 and 30 by a slight increase in amidase activity, and greater increases compared with nonflocculent populations in activities of leucine aminopeptidase, α-mannosidase, and proteinase C. Activities of proteinases A and B showed no correlation with acquisition of flocculating ability.
A new gene involved in expression of fructose-1, 6-diphosphate aldolase activity in Escherichia coli
Authors: Atherly Alan G. , Russell Paul
Published: April 2010

A new gene, fdaB, has been mapped by transduction and partial diploid analyses and is located adjacent to argA at 59.9 min on the Escherichia coli recalibrated linkage map. This gene is involved in expression of fructose-1, 6-diphosphate aldolase activity and indirectly in ribosomal RNA synthesis. The temperature-sensitive mutant strain AA-157, containing the defective gene product of fdaB, accumulates high concentrations of fructose 1, 6-diphosphate at the nonpermissive temperature.
A new nitrogen-fixing Clostridium species from a high Arctic ecosystem
Authors: Jordan D. C. , McNicol Patricia J.
Published: April 2010

A hitherto undescribed species of yellow-pigmented, Gram-negative Clostridium sp., possessing nitrogenase activity, has been isolated from a number of sampling sites on the Truelove Lowland of Devon Island in the Canadian high Arctic. This bacterium, tentatively designated Clostridium arcticum sp. nov., accounted for 19% of all isolates recovered which were capable of anaerobic nitrogen fixation.
Enhancement of tissue damage by Candida albicans in cortisone or nitrogen mustard-treated mice
Authors: Oblack Donna L. , Schwarz Jan , Holder Ian Alan
Published: April 2010

Mice were either rendered leukopenic by administration of nitrogen mustard or were treated with cortisone prior to intravenous challenge with Candida albicans. Leukopenic animals died five times faster following Candida challenge than untreated controls and also had significantly higher serum levels of the enzyme creatine phosphokinase. Similarly, when Candida infection occurred in cortisone-treated mice, mortality rates were markedly accelerated and serum levels of creatine phosphokinase and blood urea nitrogen were significantly higher than those found in untreated animals. Severe lesions and large numbers of Candida were observed in tissue sections of heart, kidney, and stomach from cortisone-treated animals. These data indicate that damage to host tissues is one manner by which Candida contribute to the morbidity of immunosuppressed animals.
A modified pork plasma agar for the enumeration of Staphylococcus aureus in foods
Authors: Hauschild A. H. W. , Park C. E. , Hilsheimer R.
Published: April 2010

The coagulase reaction of Staphylococcus aureus on the PPSA (pork plasma for S. aureus) agar of Devoyod et al. was found to be fibrinogen-deficient. By including bovine fibrinogen (BFG) in the medium, the fibrin halos around S. aureus colonies became more distinct, preparations of pork plasma previously unacceptable for inclusion in the original PPSA agar were performing well, and the amount of pork plasma required in PPSA agar could be reduced by nearly 90%.In the modified medium, designated PPF (pork plasma fibrinogen) agar, the agar base (Baird–Parker agar without egg yolk) was unchanged. After surface plating, the base was covered with 8 mL of a modified overpour agar: 2.5% pork plasma, 0.38% BFG. and 0.0015% soy trypsin inhibitor in 0.7% Bacto agar.Most S. aureus strains could be enumerated after 24 h of incubation at 35 °C; the others required 44 h. Without soy try spin inhibitor, a number of strains showed considerable fibrinolysis between 24 and 44 h of growth; this activity was neutralized by the inhibitor.The S. aureus counts of 27 food samples on PPF agar were essentially the same as the confirmed S. aureus counts obtained by the Baird–Parker method.
Characterization of two Salmonella newport bacteriophages
Authors: Moazamie N. , Ackermann H.-W. , Murthy M. R. V.
Published: April 2010

Salmonella newport phages 16–19 and 7–11 have very long heads and are members of two rare and so far little-known phage groups. Both produce various morphological aberrations. Preparations of phage 7–11 contain numerous polyheads and about 0.4% short heads belonging to nine size classes. In addition, one giant phage particle was observed. The head of phage 7–11 seems to be an icosahedron which became elongated by adding successive rows of subunits. Phages 16–19 and 7–11 have buoyant densities in CsCl of 1.43 and 1.48 g/mL and particle weights of 103 and 204 × 106 respectively. Both viruses contain double-stranded DNA, internal proteins, and sugars. Phage 16–19 contains 46.5% DNA of 35 × 106 molecular weight, and glucose. Phage 7–11 contains 47.5% DNA of 108 × 106 molecular weight, and mannose. Base compositions of phage and S. newport DNAs were determined from buoyant densities, melting point, and acid hydrolysis. Phage 16–19 contains 5.4% 5-methylcytosine.
The mitogenic activity of lipopolysaccharide for spleen cells from germfree, conventional, and gnotobiotic rats
Authors: Wells Carol , Balish Edward
Published: April 2010

Spleen cells from germfree rats, conventionally reared rats, and gnotobiotic rats associated with two Pseudomonas species gave no positive blastogenic response when incubated with each of four lipopolysaccharide (LPS) preparations from Escherichia coli, with glycolipid extracted from Salmonella minnesota R595 or with S. minnesota R595 lipid A. However, spleen cell preparations from athymic mice demonstrated a positive blastogenic response when incubated with E. coli LPS. Removal of adherent cells from germfree and conventional-flora rat spleen cells did not increase the mitogenic activity of LPS for nonadherent cells (< 0.5% esterase-positive cells). All rat spleen cell preparations gave positive blastogenic responses to phytohemagglutinin and concanavalin A. This study indicates that LPS may not be a mitogenic agent for rat spleen cells.
Antibiotic production by Pseudomonas reptilivora as a phage conversion
Authors: Martinez-Molina E. , Olivares J.
Published: April 2010

The ability of Pseudomonas reptilivora to produce three broad-spectrum antimicrobial substances is easily lost when bacteria are subcultured. The study of the antibiotic production under defined culture conditions has shown that the biosynthesis of these substances depends upon the presence of a temperature-sensitive temperate phage. Antibiotic production is lost after phage induction.
Catabolite repression-resistant mutants of Bacillus subtilis
Authors: Takahashi I.
Published: April 2010

Mutants of Bacillus subtilis that are able to sporulate under the condition of catabolite repression were isolated by a simple selection technique. The mutants used in the present study were able to grow normally on minimal medium with ammonium sulphate as the nitrogen source and glucose as the carbon source. Studies carried out with these mutants show that there is no close relation between catabolite repression of an inducible enzyme, acetoin dehydrogenase, and that of sporulation. Certain mutants are able to sporulate in the presence of all the carbon sources tested but some mutants are resistant only to the carbon source used in isolation. It is suggested that several metabolic steps may be affected in catabolite repression of sporulation.
Scanning electron microscopy of Acholeplasma colonies on agar
Authors: Polak-Vogelzang Anna A. , Samson Robert A. , Leeuw Gerard T. N. De
Published: April 2010

The colony formation and morphology of Acholeplasma laidlawii and of an Acholeplasma species was studied by scanning electron microscopy. In the colonies of both Acholeplasma spp. large irregularly shaped cells, spherical cells, chains of beads, and long filaments with small bulbous distensions were seen. The membrane of some of the large cells seemed to be perforated, giving the cell a pitted appearance.
Purification and some properties of uridine diphosphate N-acetylglucosamine pyrophosphorylase from Neurospora crassa
Authors: Yamamoto Kenji , Moriguchi Mitsuaki , Kawai Hiroyasu , Tochikura Tatsurokuro
Published: April 2010

Uridine diphosphate N-acetylglucosamine pyrophosphorylase (EC. 2.7.7.23) of Neurospora crassa has been purified approximately 210-fold with dithiothreitol as the stabilizing agent by use of chromatographic techniques. The enzyme preparation appeared to be homogeneous when subjected to electrophoresis. The molecular weight was estimated as approximately 37 000 by gel filtration. The enzyme had an isoelectric point around pH 4.4.Maximum activity of the enzyme was observed at pH7.5. The enzyme required Mg2+, which may be replaced by other divalent cations such as Mn2+ and Co2+ for lesser degrees of effectiveness. The enzyme was strictly specific for UDP-N-acetylglucosamine as the substrate. The estimated values of Km were 2.2 mM for UDP-N-acetylglucosamine and 5.4 mM for inorganic pyrophosphate.The enzyme activity was highly stimulated by the addition of dithiothreitol or dithioerythritol but was lost by sulfhydryl inhibitory reagents.
Quantitative ecology of psychrophilic bacteria in an aquatic environment and characterization of heterotrophic bacteria from permanently cold sediments
Authors: Leduc L. G. , Ferroni G. D.
Published: April 2010

Aerobic heterotrophic bacteria, anaerobic heterotrophic bacteria, ammonifying bacteria, sulfur-oxidizing bacteria, and sulfate-reducing bacteria were quantitated in Fairbank Lake, an oligotrophic to mesotrophic lake with a permanently cold hypolimnion, as a function of depth in three seasons. Representatives of each physiological group were recovered at an incubation temperature of 2 °C and for all the physiological groups the 2 °C counts were usually higher than the 37 °C counts, although sulfate-reducing bacteria were not recoverable at an incubation temperature of 37 °C. In addition, the numbers of each physiological type were generally higher in the sediments than in the water column, except in the case of sulfate-reducing bacteria for which the counts were low and often below the detection limit. Aerobic heterotrophic bacteria usually outnumbered the other physiological groups surveyed, and winter minima were characteristic of some of the physiological groups. A relatively stable density of anaerobic heterotrophic bacteria, as a function of sediment depth, was observed when the incubation temperature was 2 °C. At 37 °C, these anaerobes were not detected, and this was true for sulfate-reducing bacteria at both temperatures.Heterotrophic bacterial isolates from the permanently cold sediments were examined with regard to Gram reaction, the obligate or facultative nature of anaerobes, ability to use ecologically important substrates, psychrophilic type, and temperature range for growth. Isolates recovered at 2 °C were predominantly Gram-negative bacilli, whereas isolates recovered at 37 °C were predominantly Gram-positive bacilli. The anaerobic isolates were mainly Gram-positive bacilli regardless of the isolation temperature, and most of those examined were obligately anaerobic. Many of the isolates tested were positive for gelatinase, chitinase, amylase, and lipase, but none was positive for cellulase. Most of the sediment isolates were facultatively psychrophilic and a considerable fraction of the 37 °C isolates were facultative psychrophiles.
A temperature-gradient technique for the elimination of antibiotic resistance
Authors: Groves David J.
Published: April 2010

A technique was developed which facilitates the application of elevated temperatures to strains of unknown heat sensitivity during attempts to eliminate antibiotic resistance. Cultures were subjected to a temperature gradient and the lowest temperatures which inhibited growth were found to be highly efficient in the elimination of gentamicin resistance in several strains of Staphylococcus aureus and S. epidermidis.
Mycelial lipids as an aid in identifying rust fungi in culture—Cronartium fusiforme
Authors: Weete J. D. , Kelley W. D. , Hollis C. A.
Published: April 2010

The sterol and fatty acid content of mycelium from germinating basidiospores of Cronartium fusiforme was determined. The mycelium contained stigmast-7-enol, fungisterol, and possibly stigmasta-5,7-dienol. No ergosterol was detected. The mycelium contained the expected fatty acids and low relative proportions of 9,10-epoxyoctadecanoic acid. The absence of ergosterol, and presence of the epoxy C18 acid and sterols typical of certain rust spores may be used for a relatively rapid confirmation of rust fungi in culture. Based on these chemical criteria, yeast-like cells isolated from the cultures of germinating basidiospores appear not to be C. fusiforme.
COMPUTING CARDIAC RECOVERY MAPS FROM ELECTROGRAMS AND MONOPHASIC ACTION POTENTIALS UNDER HETEROGENEOUS AND ISCHEMIC CONDITIONS
Authors: SCACCHI SIMONE , FRANZONE PIERO COLLI , PAVARINO LUCA F. , TACCARDI B.
Published: April 2010

The currently available techniques to investigate the 3D sequence of activation and recovery in the cardiac atria and ventricles, with high spatial resolution, are based on extracellular electrical recordings. The goal of the present work is to provide an extensive quantitative analysis of the accuracy level of commonly used recovery time (RT) markers, under heterogeneous and pathological conditions of the myocardial tissue, such as myocardial ischemia. A widely used technique is based on unipolar electrograms (EGs); an alternative technique is based on hybrid monophasic action potentials (HMAPs), obtained as the potential difference between a permanently depolarized site and an exploring site. The RT markers derived from EGs and HMAPs are compared with two transmembrane action potential (TAP) markers considered here as gold standards for the fastest and final recovery phase, respectively. The analysis is based on 3D numerical simulations of the action potential propagation in anisotropic and insulated cardiac blocks, modeled by the Bidomain system coupled with the Luo–Rudy I membrane model. These demanding simulations have been made possible by recent advances in computing power and multilevel Bidomain solvers. The results show that the extracellular RT markers considered are reliable estimates of the gold standard TAP markers, with low relative mean discrepancies and high correlation coefficients. We also investigate the capability of the markers to discriminate different transmural dispersions of recovery times and action potential durations. In some specific pathological cases when the EG markers fail, the HMAP markers may offer reliable alternatives.
A SEQUENCE OF DEGREE ONE VASSILIEV INVARIANTS FOR VIRTUAL KNOTS
Authors: HENRICH ALLISON
Published: April 2010

For ordinary knots in R3, there are no degree one Vassiliev invariants. For virtual knots, however, the space of degree one Vassiliev invariants is infinite-dimensional. We introduce a sequence of three degree one Vassiliev invariants of virtual knots of increasing strength. We demonstrate that the strongest invariant is a universal Vassiliev invariant of degree one for virtual knots in the sense that any other degree one Vassiliev invariant can be recovered from it by a certain natural construction. To prove these results, we extend the based matrix invariant introduced by Turaev for virtual strings to the class of singular flat virtual knots with one double-point.
SOME IRREDUCIBLE REPRESENTATIONS OF THE BRAID GROUP 𝔹n OF DIMENSION GREATER THAN n
Authors: EGEA CLAUDIA MARÍA , GALINA ESTHER
Published: April 2010

For any n ≥ 3, we construct a family of finite-dimensional irreducible representations of the braid group 𝔹n. Moreover, we give necessary conditions for a member of this family to be irreducible. In particular we give a explicitly irreducible subfamily (ϕm, Vm), 1 ≤ m < n, where [Formula: see text]. The representation obtained in the case m = 1 is equivalent to the standard representation.
Length and Timescales of Rift Faulting and Magma Intrusion: The Afar Rifting Cycle from 2005 to Present
Authors: Ebinger Cynthia , Ayele Atalay , Keir Derek , Rowland Julie , Yirgu Gezahegn , Wright Tim , Belachew Manahloh , Hamling Ian
Published: April 2010

Although fault and magmatic processes have achieved plate spreading at mid-ocean ridges throughout Earth's history, discrete rifting episodes have rarely been observed. This paper synthesizes ongoing seismic, structural, space-based geodetic, and petrologic studies from the subaerial Red Sea rift in Ethiopia where a major rifting episode commenced in September 2005. Our aims are to determine the length and timescales of magmatism and faulting, the partitioning of strain between faulting and magmatism, and their implications for the maintenance of along-axis segmentation. Most of the magma for the initial and subsequent 12 intrusions was sourced from the center of the Dabbahu-Manda Hararo rift segment. Strain is accommodated primarily by axial dike intrusions fed from mid-segment magma chamber(s). These findings show that episodic (approximate century interval), rapid opening of discrete rift segments is the primary mechanism of plate boundary deformation. The scale (∼65 km × 8 km) and intensity of crustal deformation (∼6 m), as well as the volume of intrusive and extrusive magmatism (>3 km3), provokes a re-evaluation of seismic and volcanic hazards in subaerial rift zones.
The Formation of Martian River Valleys by Impacts
Authors: Toon Owen B. , Segura Teresa , Zahnle Kevin
Published: April 2010

We explore the role of large impacts in creating the Martian valley networks. Recent dating shows that some large impact basins are contemporaneous with the valley networks. The mass deposited (and volatiles released) by impacts is large, and comparable with the mass from the Tharsis volcanic construct. Steam atmospheres formed after large impacts can produce more than 600 m of rainfall, followed by rainfall from water-vapor greenhouse atmospheres, and snowmelt. The erosion rates from impacts that created the currently visible craters are somewhat less than the erosion rates suggested for the Noachian (4.2 to 3.82 Gya). There are several possible explanations for this difference, and it is possible that erosion rates are overestimated because the burial of small craters by global debris layers from impacts has not been considered. Rainfall after the Noachian was low because the impact rate and CO2 pressure declined. We suggest tests of the hypothesis that impacts caused the river valleys.
The Late Devonian Gogo Formation Lägerstatte of Western Australia: Exceptional Early Vertebrate Preservation and Diversity
Authors: Long John A. , Trinajstic Kate
Published: April 2010

The Gogo Formation of Western Australia preserves a unique Late Devonian (Frasnian) reef fauna. The exceptional three-dimensional preservation of macrofossils combined with unprecedented soft-tissue preservation (including muscle bundles, nerve cells, and umbilical structures) has yielded a particularly rich assemblage with almost 50 species of fishes described. The most significant discoveries have contributed to resolving placoderm phylogeny and elucidating their reproductive physiology. Specifically, these discoveries have produced data on the oldest known vertebrate embryos; the anatomy of the primitive actinopterygian neurocranium and phylogeny of the earliest actinopterygians; the histology, radiation, and plasticity of dipnoan (lungfish) dental and cranial structures; the anatomy and functional morphology of the extinct onychodonts; and the anatomy of the primitive tetrapodomorph head and pectoral fin.
The Lithosphere-Asthenosphere Boundary
Authors: Fischer Karen M. , Ford Heather A. , Abt David L. , Rychert Catherine A.
Published: April 2010

Seismological models of upper-mantle structure are providing new constraints on the physical and chemical properties that differentiate the lithosphere from the asthenosphere. A wide variety of studies are consistent with an oceanic lithosphere that corresponds to a dry, chemically depleted layer over a hydrated, fertile asthenosphere. At the lithosphere-asthenosphere boundary beneath oceans and many Phanerozoic continental regions, observed seismic velocity gradients require a contrast in mantle hydration, fertility, and/or melt content, perhaps in combination with a vertical gradient in velocity anisotropy. Beneath cratons, evidence is growing for a deeper—but globally ubiquitous—asthenosphere. Some studies conclude that the cratonic lithosphere-asthenosphere boundary is gradual enough to be matched by a purely thermal gradient, whereas others indicate a more rapid transition and a contrast in composition or perhaps melt content.