摘要:

Inbred mouse strains show characteristic susceptibility toS.typhimuriuminfections. The sensitivity of the same strains to endotoxin is not parallel. While C3H/He J and C57B1/6J mice were highly susceptible to infection they showed more resistance to purified endotoxin than A/J, a mouse strain relatively resistant to infection. These findings suggest that the death of mice duringS.typhimuriuminfection is not due only to toxic effects of its lipopolysaccharide.

ISSN:0008-4166    

DOI:10.1139/m73-125

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Eight fungicides used in soil treatments were assayed for their effect against three species of bacteria, two of actinomycetes, and three of fungi at intervals over a 32-week period. Methylmercury dicyandiamide (MMDD) was the only fungicide that showed some inhibitory effect at 1 ppm. MMDD and Hoe 2874 were the most effective fungicides followed by Chemagro B1843, thiram, and maneb in decreasing order of effectiveness. Captan with low solubility and two insoluble fungicides showed little or no activity. No fungicide at 1 or 10 ppm persisted for over 3 weeks. At 100 and 1000 ppm some fungicides persisted for periods extending beyond 32 weeks. The eight fungicides differed both quantitatively and qualitatively in their ability to inhibit or stimulate the various test organisms. The method is described and the effect of fungicides in soil treatment on the general microflora besides the soil pathogens is discussed.

ISSN:0008-4166    

DOI:10.1139/m73-126

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

An enzyme complex which hydrolyzed the KCl soluble carrageenan extracted from the red algaChondrus crispushas been isolated from the cell-free medium of a culture ofPseudomonas carrageenovoragrown on this polysaccharide. Three hydrolases could be separated. Fraction I, which caused a rapid decrease in the specific viscosity of the polysaccharide preparation with only minimal release of reducing sugar, could be distinguished from fraction II chromatographically on Sephadex G-100 and electrophoretically on agarose gel. Fraction IIacaused release of reducing sugar at pH 6.2, which activity was depressed at pH 7.5. Fraction IIbexhibited viscometric activity only at both pH 6.2 and pH 7.5. Fraction IIahad a sharp pH optimum at pH 6.2 and a temperature optimum at 28°. All hydrolases were inactivated by freezing, by dialysis against distilled water, by heating at 35° for 30 min, and by Hg2+and 0.0001 mM EDTA. When fraction II (aandb) isolated after chromatographic resolution on Sephadex G-100 was incubated at pH 6.2 with KCl soluble carrageenan fromC.crispus, products which hadRgalvalues of 0.74 and 0.17 were detected, were sulfated, and contained no 3,6-anhydrogalactose.

ISSN:0008-4166    

DOI:10.1139/m73-127

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Conidial and mycelial cell walls ofPenicillium notatumwere found to be chemically different, the main differences being in the distribution of amino acids, neutral sugars, and amino sugars. The amino acid content was higher in conidial than in hyphal walls but individual amino acids found in spore and mycelial walls were essentially the same, except for basic amino acids (histidine, arginine, and lysine) of which only traces were present in mycelial walls.Four neutral sugars (glucose, galactose, mannose, and rhamnose) were detected in walls of resting spores, but rhamnose was absent at other stages of germination. Galactose was the most abundant sugar in walls of resting spores, while glucose was the main component of hyphal walls. Only one hexosamine (glucosamine) was found in walls of resting and swollen spores but galactosamine was present in walls of germinating spores and mycelium. The content of both amino sugars greatly increased during germination.

ISSN:0008-4166    

DOI:10.1139/m73-128

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

To study the changes in the cell wall ofPenicillium notatumduring germination, thin sections of resting, swollen, and germinating spores, and mycelium were compared with thin sections of the isolated cell walls. In the cell wall of resting spores four distinct layers were found. The outermost layer of the cell wall of resting spores was released during swelling and the two inner layers were extended to form the cell wall of the germ tube. The cell wall of young germ tubes had only two layers but a new electron-dense layer was formed later on the outside. Mycelial cell walls which appeared thinner than those of conidia showed three distinct layers. Large mitochondria that divide during germination were present in both resting and swollen spores. Two different types of vacuoles were found, both of which decreased in size and in number during germination. Endoplasmic reticulum was almost absent in resting spores but increased substantially during swelling.

ISSN:0008-4166    

DOI:10.1139/m73-129

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Carbohydrate metabolism in the growing plasmodial phase ofPhysarum flavicomumwas studied in partially defined media using the radiorespirometric technique and specifically labeled14C-substrates. The Embden–Meyerhof–Parnas (EMP) – tricarboxylic acid cycle (TCA) and the pentose phosphate pathways are the routes by which glucose is used by this myxomycete. The replacement of the usual citrate–phosphate buffer by succinate–phosphate results in a decreased uptake of14C-glucose from the medium and a corresponding decline in the rate of interval14CO2evolution. The addition of an inorganic nitrogen source (ammonium nitrate) to the medium also decreases the rate of carbohydrate metabolism and alters the relative participation of the pathways by favoring the EMP–TCA. Supplementing the medium with cyclic-3′-5′-adenosine monophosphate produces a transient stimulation of the rate of metabolism by the EMP–TCA. The Plasmodium is relatively impermeable to gluconate and pyruvate and does not readily metabolize amino acids.

ISSN:0008-4166    

DOI:10.1139/m73-130

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Soil bacteria enter the digestive tract of wireworms at ecdysis through the dorsal exuvial split and ecdysial space.Pseudomonas aeruginosa, a potential pathogen of insects, multiplies in the enteron, but many are killed within it. The mucopeptide layer of the bacterial cell wall is affected early in the degenerative process.A surface epithelial mucoid layer provides a temporary protective barrier for the midgut epithelium against the bacteria. The bacteria affect the fine structure of the host midgut epithelium in three primary ways. (1) The cells take up and retain fluids in the cytoplasm and membrane-bound vacuoles to the point of apical rupture; the selective permeability of the membranes of the cell and vacuoles appears to be affected. (2) The surface mucoid covering is degraded, the exposed plasma membrane is disrupted, and a lytic erosion of the exposed cytoplasm occurs opposite bacterial colonies. Lesions thus form in the midgut epithelium, and could lead to perforation of the wall at these points. (3) Pathological changes occur in various cell organelles, the most striking of which are an increase in abundance of rough endoplasmic reticulum (RER) and cytoplasmic ribosomes, and a transposition of membrane material from mitochondria and Golgi complexes to RER. The functional implications of these pathological changes in fine structure are discussed.

ISSN:0008-4166    

DOI:10.1139/m73-131

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Cells injured by heating at 52C for 15 min in sodium (Na cells) or potassium phosphate buffer (K cells) were allowed to grow and recover in media containing 0, 0.1%, and 1.0% glucose. Growth, acid, and enterotoxin B production was followed and compared with that of unheated control cells. Control cells growing in 0 and 0.1% glucose first lowered the pH, but injured cells did not. Straight lines were obtained from growth experiments when the ratio enterotoxin B/pH versus time was plotted. Statistical analysis of the slopes showed that Na cells differed from K cells. In 1.0% glucose, Na cells produced less acid than K cells. Na cells were 80%, control cells were 90%, and K cells were 99% repressed in their enterotoxin B synthesis. At all glucose levels, the lag phase of Na cells was about 2 h shorter than that of K cells. Heat injury caused a 30–40% loss of K+, but Na cells gained Na+(34%) and K cells lost Na+(28%). The K/Na ratio of Na cells was 2.75 and that of K cells was 15.75. It is argued that this difference could account for the differences observed between Na cells and K cells but cannot account for the total injury phenomenon.

ISSN:0008-4166    

DOI:10.1139/m73-132

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The particulate material (intact and dissociated phycobilisomes), adjacent to the thylakoids ofPlectonema boryanumandCalothrix parietina, was examined in thin sections and in freshly prepared C-phycocyanin extracts. For the latter a method was developed using spheroplasts of log-phase cells. When examined by sedimentation velocity centrifugation, the sedimentation coefficients of the rapidly extracted C-phycocyanin were found to be 18 S and 5 S. Also, a 10-S boundary was observed withP.boryanum. WhenC.parietinawas grown under red light the 18-S aggregates increased to 20 S. The 18 S particles, in electron micrographs of negatively stained preparations, displayed eight subunits surrounding a central one. The possibility that some subunits fall out of the plane of view is contemplated in proposing a dodecamer arrangement for such particles. The 20-S particles were also examined by electron microscopy. However, the precise number of monomer units associated with either the 18-S or 20-S particles has not yet been ascertained. Thin sections of intact algal cells are presented to demonstrate the presence of phycobilisomes along the outer faces of the thylakoid membranes.

ISSN:0008-4166    

DOI:10.1139/m73-133

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Bacteriophage (S1) ofErwinia amylovora, isolated from soil at the base of fire-blight-infected trees, was characterized by small, clear plaques onE.amylovorastrain PR1 and hazy plaques of the same size on a closely related, yellow, saprophytic bacterium, Y, which was isolated together with PR1 from the diseased trees. Phage S1 plated with optimal efficiency at 10C on PR1 and at 28C on Y was relatively unstable to storage at temperatures typical of summer and to ultraviolet (UV) irradiation, and lysogenized Y but not PR1. Pathogenicity tests in pear slices demonstrated that symptom development was (i) delayed when mixtures of either PR1 and phage S1 or PR1 and Y were inoculated, (ii) delayed when a culture of a phage-resistant mutant of PR1 was inoculated, and (iii) prevented from appearing at all when PR1 and the lysogenic form of Y, Y (S1), were inoculated together. Strain Y was easily lysogenized and Y (S1) released phage spontaneously and after UV irradiation. It is suggested that the yellow saprophyte, which is invariably isolated from fruit trees withE.amylovora, may frequently occur in its lysogenic form in nature and serve as a reservoir of phage which may exert some influence on the occurrence and severity of fire-blight disease.

ISSN:0008-4166    

DOI:10.1139/m73-134

出版商:NRC Research Press    

年代:1973

数据来源: NRC