摘要:

The fatty acid composition of the total and polar lipid fractions ofChoanephora cucurbitarumgrown under different cultural conditions were analyzed by thin-layer and gas–liquid chromatography. It was observed that temperature, age, pH, and light influenced the degree of unsaturation, this being due mainly to changes in the γ-linolenic acid concentration. The conditions used in this study did not alter the qualitative profile of fatty acids normally present in the organism. Neither did these conditions stimulate the production of further long-chain fatty acids (C20–C26) beyond γ-linolenic acid (C18:3) as reported earlier using growth media containing glutamic acid. The fatty acid pattern of lipid fractions though the same qualitatively, differed quantitatively. The polar lipid fractions, phosphatidyl choline, phosphatidyl ethanolamine, and diphosphatidyl glycerol showed an appreciable variation in γ-linolenic acid content under different cultural conditions. The degree of unsaturation of the various lipid fractions decreased with increases in temperature, light intensity, and pH, but within each treatment the same pattern of decreasing degree of unsaturation with increasing age was observed. The significance of these observations is discussed.

ISSN:0008-4166    

DOI:10.1139/m76-070

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Streptococcus boviswas cultured in a synthetic medium with three concentrations of sucrose. Initial viscosity of the media was 1.5 centipoise (cp). After incubation for 8 h, the viscosity of the medium with 0.5% sucrose was unchanged, that with 3% sucrose had increased to 8 cp, and that with 6% sucrose to 112 cp. Similar results were found with a rumen fluid medium. A slimy material, responsible for increased viscosity of these cultures, was digested by dextranase. The material appeared as a complex system of intercellular fibers when viewed under the electron microscope after freeze-etching. With proteins and other polymers released from lysed bacteria, this slimy material may contribute directly to increased viscosity and foam formation. In addition to these intercellular fibers, each cell was surrounded by a fibrous capsule that was not digested by dextranase. This capsule stained with lead citrate and uranyl acetate, but not with ruthenium red. The amount of capsular material produced was similar whether the media contained 0.5, 3.0, or 6% sucrose.

ISSN:0008-4166    

DOI:10.1139/m76-071

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Cellular and free lipopolysaccharides obtained fromNeisseria catarrhalisandBranhamella catarrhaliswere found to be essentially identical. Both cellular and free lipopolysaccharides contained core-oligosaccharides of the following composition:D-glucose (4 mol),D-galactose (1 mol), 2-amino-2-deoxy-D-glucose (1 mol), and 3-deoxy-D-manno-octulosonic acid. Aldoheptose and phosphate components were below levels of detection. Several physical methods indicated that all core-oligosaccharide preparations were identical. Lipid A preparations from cellular and free lipopolysaccharides of both organisms were qualitatively and quantitatively similar; they were composed of decanoic acid, dodecanoic acid, 3-hydroxy dodecanoic acid, 2-amino-2-deoxy-D-glucose, phosphate, and ethanolamine. The results tend to justify the transfer ofNeisseria catarrhalisto the genusBranhamella.

ISSN:0008-4166    

DOI:10.1139/m76-072

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Bacillus stearothermophilusNCA 2184 lost viability and subsequently released cytoplasmic components when suspended in 0.1 Mtris(hydroxymethyl)aminomethane (Tris) buffer (pH 7.2) and incubated at 60 °C. Cell lysis was prevented by the addition of 10 mMCaCl2to the Tris-buffer suspension. Cells which were incubated under anaerobic conditions for 20 min in the growth medium before they were collected were stable in the Tris-buffer suspension without added calcium. Anaerobic incubation effected an increase in membrane cardiolipin which appeared to be related to the increase in the thermostability of the cells.

ISSN:0008-4166    

DOI:10.1139/m76-073

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The ultrastructure ofStreptococcus mutans, serotypesa–e,S.sanguis,S.mitis, andS.salivariusHHT, were examined by the techniques of thin-sectioning and freeze-etching. The cell walls varied in width between 15 and 46 nm and were covered with an electron-dense fibrillar or fuzz layer. The cytoplasmic membrane was in close association with numerous mesosomes which were, in turn, either closely associated or in contact with the bacterial chromosome. In freeze-etch replicas, the outermost layer of the cell wall was fibrous, and the cytoplasmic membrane was covered with particles composed of several subunits. Both particle-clusters and particle-free areas occurred on the surfaces of the cytoplasmic membrane, as well as a crystalline array in the ground plasm of the cell.

ISSN:0008-4166    

DOI:10.1139/m76-074

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Mechanically isolated, cytoplasm-free cell walls ofChoanephora cucurbitarumwere analyzed qualitatively and quantitatively by use of microchemical methods, infrared spectrophotometry, and X-ray diffraction. Chemical analysis of cell wall revealed the presence of chitin (17%), chitosan (28.4%), neutral sugars (7.2%), uronic acid (2.4%), proteins (8.2%), and lipids (13.8%). The structure of hyphal wall, investigated by electron microscopy of shadowed replicas before and after alkali-acid hydrolysis, showed two distinct regions: microfibrillar and amorphous. The microfibrils, which were composed of mainly chitin, were organized into two distinct layers; an outer, thicker layer of randomly oriented microfibrils, and an inner, thin layer of parallel microfibrils. In its structure and chemical composition the cell wall ofC.cucurbitarumresembles those of other zygomycetous fungi.

ISSN:0008-4166    

DOI:10.1139/m76-075

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The paper provides detailed ultrastructural observations on nuclear division in the smut fungusUstilago violaceaand is based on previous light-microscopic work outlining the division in living and stained cells. The division as in many other Basidiomycetes is not intranuclear, but occurs within a partially disrupted membrane. The division takes place after migration of most of the nucleus into the bud cell, after limited breakdown of the nuclear membrane, and after the formation of a spindle between two spindle-pole bodies (SPB). The remaining part of the nucleus containing the nucleolus is left behind in the parent cell and degenerates there. The SPB, as in other Basidiomycetes, is a dome-shaped relatively structureless body, quite distinct from the flat plaques of many Ascomycetes and the elaborate centrioles of Phycomycetes. The SPB divides shortly before migration into the daughter cell and invariably is located at the apex of the migrating nucleus. Nuclear division is completed when the two masses of chromatin clustered about each of the SPB's are separated as the spindle elongates. One daughter nucleus reforms in the bud and the other is reformed in the mother cell.Cells fixed and stained by conventional light-microscopic methods were examined in the light of the electron-microscopic observations to determine whether these procedures induce artefacts. Aceto-orcein and Giemsa when used cold were found to produce relatively artefact-free preparations. However, previous results in which the cells were warmed gently in these stains are now seen to contain artefacts in the form of contracted chromatinic granules often arranged in chains. These artefacts may provide useful information but clearly they must be interpreted cautiously until the nature of the changes induced by heating are known.

ISSN:0008-4166    

DOI:10.1139/m76-076

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

In unbudded cells of the anther smut fungusUstilago violaceathere is a dome-shaped spindle-pole body (SPB) consisting of a core 0.1 μm in diameter surrounded by a ribosome-free region 0.3–0.4 μm in diameter lying in a pocket of the nuclear membrane. After budding the nucleus moves towards the bud and begins to rotate rapidly. At about this stage the SPB divides into two parallel bars each about 0.1–0.15 μm in diameter and 0.3 μm long, separated by a distance of about 0.3 μm. Microtubules associated with the nuclear membrane but not with the SPB are present at the time of nuclear rotation. These microtubules disappear when rotation stops. Microtubules attached to the SPB are found during migration of the chromatinic portion of the nucleus into the bud cell. These microtubules disappear when migration stops and the nuclear membrane begins to break down. The twin SPB bars appear to move into the nucleus through a break in the membrane and begin to move apart forming a spindle about 1 μm long. Chromosomal microtubules (one per kinetochore) were found in several serial sections, and in addition there appeared to be several continuous microtubules present. The separation of the two chromatinic masses appeared to result from elongation of the continuous microtubules to about 3 μm long. Cytoplasmic microtubules and spindle microtubules were both found attached to the SPB as it elongated and one nucleus returned to the mother cell.The paper concludes with a discussion of the SPB as a multifunctional control center affecting nuclear migration, spindle formation, membrane breakdown and synthesis, karyogamy, conjugation, budding, chromosomal movement, replication, and disjunction.

ISSN:0008-4166    

DOI:10.1139/m76-077

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Nitrogen fixation associated with both natural grasslands and grain crops of Oregon was studied using the acetylene-reduction assay. A number of the grasses collected had some acetylene-reducing activity.Agrostis tenuisSibth. had substantially greater activity than any of the other species, with a mean rate estimated at 37 g N2fixed per hectare per day. Assuming 100 days of activity, about 3 kg of N2would be fixed per hectare per year. This quantity of nitrogen may be important in the maintenance of this species under natural conditions. Nitrogen-fixing microorganisms were isolated from the root surfaces of some of the grasses. Cultures ofBacillus macerans,Bacillus polymyxa, andEnterobacter cloacaewere isolated from wheat roots as were two cultures which have not been assigned a specific taxonomic classification. Strains of N2-fixingBacillusspecies and Gram-negative aerobic bacteria were isolated fromFestucaandAgrostis.

ISSN:0008-4166    

DOI:10.1139/m76-078

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Auxotrophs in three different races ofPyricularia oryzaewere obtained following ultraviolet mutagenesis, and tested for complementarity on minimal medium. Prototrophic growth resulted between combinations of different auxotrophs of single strains, but not between strains. The growth did not result from crossfeeding, but required at least transitory heterokaryosis. Putative diploids, i.e., large prototrophic conidia, were readily isolated from the heterokaryons. In addition, conidia with nearly every possible combination of parental markers were found, showing thatP.oryzaedoes indeed complete the parasexual cycle. The degree of genetic recombination found here may help to explain the extreme variability of this organism.

ISSN:0008-4166    

DOI:10.1139/m76-079

出版商:NRC Research Press    

年代:1976

数据来源: NRC