摘要:

A rapid technique was developed for the extraction and preparation of gas samples required for field studies of aquatic denitrification. With this method, the natural atom percent abundance of15N in air-saturated distilled water was found to be 0.370 ± 0.004 SD. Nitrogen-15 tracer experiments showed that 20% of the nitrate taken up was denitrified in 5 days in lake water samples collected after fall turnover. Under conditions conducive to denitrification, 90% of the nitrate taken up was denitrified in 2 days by pure cultures of aPseudomonasspecies.

ISSN:0008-4166    

DOI:10.1139/m74-046

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

A fungus,Aspergillus fumigatusFres., which used bark as its sole carbon and energy source, was isolated. Difficulties arose in measuring fungal growth, since the hyphae and the bark could not be separated. Measurement of the weight loss of the solid material did not quantitatively estimate fungal growth. Therefore, two methods were developed to estimate fungal mass when the carbon and energy source is particulate and contributes to the parameter used as a measure of growth. They were based on determination of nitrogen either in the solid material or in the medium. The nitrogen concentration inA.fumigatuswas found to be nearly constant throughout the growth cycle and to be independent of the carbon and nitrogen concentrations in the medium but to vary with the carbon source used.Aspergillus fumigatuswas grown at 37C as a submerged culture in salts medium with finely ground bark fromPicea abiesas sole carbon and energy source. The bark medium was heat-sterilized before inoculation with spores. The fungus utilized cellulose and hemicellulose but not lignin. Substances solubilized from the bark contributed to the growth. The yield was the same on unextracted as on water-extracted bark, although growth was delayed on the former. Growth was rapid and comparable to growth on other polymeric polysaccharides, i.e. starch.Aspergillus fumigatusdegraded 32–40% of the polymeric part of the bark within 4 days and with an economic coefficient of about 50%.

ISSN:0008-4166    

DOI:10.1139/m74-047

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

We have studied the biodegradation of melanized cells ofAureobasidium pullulansby electron microscopy. There is no difference after 6 months and 1 year of incubation.This study provides evidence for the removal of cell components, enzymatic lysis of cell wall, and the production of black granula. The appearance of subunits as part of granula was also observed surrounding the bacteria.At the earliest stage of cell decomposition ofAureobasidium pullulans(utilization of gum), fungi are active. After 6 months, micromycetes stop their activity and the bacteria degrade the wall structures and, probably, some of these bacteria also degrade the granula.The value of various techniques used to demonstrate the decomposition stages and the role of surrounding microorganisms is discussed. [Translated by the journal]

ISSN:0008-4166    

DOI:10.1139/m74-048

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Survival data were obtained onAcholeplasma laidlawiiB after exposure to ionizing radiation at various ages, pH, temperature, and supplements to the medium. TheD0value varied slightly with pH in air but much more after irradiations in N2or N2O. Replacement of the growth medium with fresh broth resulted in an increase inD0while dilution of the growth medium with Tris-NaCl 1:100 caused a decrease inD0both in air and N2. TheD0varied with the age of the culture and the temperature at the time of irradiation. In air the ratio of increment inD0(ΔD0) over the increment in temperature (ΔT) had positive values as a function of age of the cells while under N2this ratio was always negative. In N2theD0decreased in a smoothly non-linear fashion with an increase in temperature while in air it remained constant below 12° and increased linearly above that temperature at a rate equivalent to 1.65 kcal/mol. ATP was found to radioprotect the cells in N2at pH 6.3 but radiosensitize them both in air and N2at pH 7.5. The adenine nucleotides ATP, ADP, and AMP eliminated radiation-induced division delay in the cells in air. Cyclic AMP had no effect on the division delay in air but was found to synchronize cell growth.

ISSN:0008-4166    

DOI:10.1139/m74-049

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Several kinds of nutrients were perfused to soil-inoculated veneers and were found not to change significantly the frequencies of microfungi isolation, but to have more effect on the rate of strength loss. Woods supplied with small amounts of nitrogen nutrient had slight strength reductions and thus indicated the adaptability of these microfungi to such conditions.The presence of nitrogenase activity within deteriorated wood was demonstrated and this suggested that over a long period of time nitrogen-fixing microorganisms might increase the wood nitrogen content.Amino compounds present in wood were altered with nitrous acid and shown not to upset the colonization patterns or the rate of decay. Some depolymerization of the cellulose fraction with further treatment by dilute alkali and ammonia gave varied results and no apparent decay when perfused with water.Leaching the wood with dilute acid gave a decrease in nitrogen content and this again did not affect the fungal growth, but it did prevent a loss of strength when perfused with water. It might provide a method of preserving timber used in certain conditions.

ISSN:0008-4166    

DOI:10.1139/m74-050

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Cocal strain of vesicular stomatitis virus was propagated inAedes albopictusandAedes aegypticell lines. Infection of the cell lines at 30 °C resulted in a low-titered virus infection involving only a small proportion of the cell population with no cytopathic effects. Virus titers inA.albopictuswere increased by adsorption with DEAE-dextran or by increasing the temperature of incubation. Use of a high-input multiplicity of virus and incubation of cells at 37 °C resulted in 100% infection of cells, allowing an electron-microscopic study of virus development. These studies indicated that virus maturation inA.albopictuscells occurred primarily at intracytoplasmic vesicles.

ISSN:0008-4166    

DOI:10.1139/m74-051

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The growth characteristics and nuclease secretion patterns ofStaphylococcus aureus, strains UNH-15 and Foggi, were investigated. Strain Foggi grew more rapidly, but the rate of its nuclease secretion was slower than that of UNH-15. And though the terminal turbidities of both strains were about equal, the final nuclease yields of UNH-15 were 15–20% higher than Foggi's.Three chromatographically and electrophoretically separable forms of nuclease were present in the culture supernatants of these strains. Designated nucleases I, II, and III, in order of their elution from carboxymethylcellulose columns, the forms were not produced simultaneously and their relative concentrations changed during the growth cycle. During the log phase growth, I and II were produced. Near the end of this phase, III began to appear, while I and II were concurrently disappearing from the culture. Only III was present in the supernatant fluid of stationary phase cultures.Molecular sieving of the forms in G-75 Sephadex and electrophoresis in SDS-polyacrylamide indicated that the molecular weights of the I, II, and III forms were about 7 000, 14 000, and 20 000 respectively. Commercially available micrococcal nuclease appears to be electrophoretically identical with a mixture of forms II and III.

ISSN:0008-4166    

DOI:10.1139/m74-052

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

When chloramphenicol-producing cultures ofStreptomycesspecies 3022awere administered [G-14C] chorismic, [G-14C] prephenic, and [G-14C, 6-3H] shikimic acids, radiochemical yields in the antibiotic were very low (0.01–0.1%). [G-14C] chorismic and prephenic acids labeled chloramphenicol to about the same specific activity as tyrosine, aspartic acid, and glutamic acid from mycelial protein, whereas protein phenylalanine was 100 times more active. We conclude that these two substrates are unable to penetrate the cell membrane and the radioactivity incorporated enters as [G-14C] phenylpyruvic acid. Labeled shikimic acid, on the other hand, was directly incorporated into the cells. The14C:3H ratio in chloramphenicol isolated after feeding the [G-14C, 6R-3H] and [G-14C, 6S-3H] labeled forms indicated that thepro-6R-hydrogen was eliminated during ring aromatization. Antibiotic labeled from [G-14C, 6S-3H] shikimic acid was chemically degraded to 2,4,6-tribromoaniline without change in the14C:3H ratio thus establishing the specific incorporation of shikimic acid into the phenyl ring, and locating the tritium at positions ortho to the propanoid substituent.

ISSN:0008-4166    

DOI:10.1139/m74-053

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

A method is described wherebyClostridium botulinum33A and 51B spore spheroplasts are produced in two sequential steps: (1) by reducing spore coats for 3 h with 50% mercaptoacetic acid – 8 M urea – 0.01 M EDTA, and (2) by lysis of the cortex for 2 h with 500 μg/ml lysozyme in 0.01 M Tris-HCl (pH 8.0) – 0.01 M EDTA – 1 mg/ml dithiothreitol and 25% lactose added as osmotic stabilizing agent.Optical density measurements (absorption spectra) of ultraviolet (UV)-absorbing material released after submitting spheroplasts to osmotic lysis in distilled water showed absorption maxima around 270 nm (dipicolinic acid) and 260 nm (nucleic acids). Radioactivity profiles of3H-labeled TCA-insoluble material from centrifugation of alkaline sucrose gradients showed that the above schedule for obtaining spore spheroplasts resulted in optimal DNA extraction and did not cause extensive breakage of DNA.Phase-contrast microscopy indicated that spore appearance is not visibly affected by chemical coat reduction; however, spores become phase dark after treatment with lysozyme. Electron microscopy showed that after chemical reduction coat layers are less compact, of less electron density, and dissolved in some areas. Furthermore, lysozyme treatment disintegrates and to a large degree removes the cortex and structural details become visible in the core.

ISSN:0008-4166    

DOI:10.1139/m74-054

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Hydrostatic pressure has been shown to inhibit protein synthesis inEscherichia coliby inhibiting amino acid activation and polypeptide synthesis in cell-free systems. Pressure may decrease translational ambiguity by suppressing any non-specific activity of phenylalanyl-tRNA synthetase and by preferentially decreasing the stability of leucyl-tRNA.

ISSN:0008-4166    

DOI:10.1139/m74-055

出版商:NRC Research Press    

年代:1974

数据来源: NRC