摘要:

Several attempts were made to colonize the alimentary tract and infect germfree BALB/c mice and germfree Sprague-Dawley rats with two human isolates ofHelicobacter pylori. The alimentary tracts of mice, sacrificed at intervals between 1 day and 20 weeks after oral challenge, were culture negative forH.pylori. The alimentary tract, kidney, liver, and mesenteric lymph nodes were culture negative forH.pylori5 h after intravenous challenge. Growth ofH.pyloriwas inhibited by homogenates of murine stomach, small intestine, liver, and mesenteric lymph nodes. Germfree rats and mice do not appear to be readily colonized or infected by human strains ofH.pylori.Key words:Helicobacter pylori, germfree mice, congenitally immunodeficient mice.

ISSN:0008-4166    

DOI:10.1139/m90-041

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

A genomic library of thePseudomonas putidastrain GR12-2 was screened to identify both genus-universal and strain-specific 8-kilobase inserts. The genus-universal clone (pAM141), in combination with the restriction enzymesEcoRI,PstI, andPvuII, was used to generate unique restriction fragment length polymorphisms for 20 related plant growth promoting rhizobacteria and seven reference strains. Strain restriction fragment length polymorphism profiles based on the genus-universal clone pAM141 allow positive identification of individual pseudomonad strains. The strain-specific clone (pAM227) clearly distinguished the parent strain (GR12-2) from 16 other pseudomonad strains, including 8P.putida, 7P.fluorescens, and 1P.cepacia. pAM227 may be useful for monitoring the fate of theP.putidastrain GR12-2 in the environment.Key words: pseudomonads, rhizobacteria, restriction fragment length polymorphism, strain identification.

ISSN:0008-4166    

DOI:10.1139/m90-042

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Candida albicansformed germ tubes when exposed to air containing 5 to 15% carbon dioxide (CO2). The CO2-mediated germ tube formation occurred optimally at 37 °C in a pH range of 5.5 to 6.5. No germ tubes were produced at 25 °C, even when the optimal concentration of CO2(10%) was present in the environment. The requirement of CO2for germ tube formation could be partially substituted by sodium bicarbonate but not by N2. Carbon dioxide was required to be present throughout the entire course of germ tube emergence suggesting that its role is not limited to an initial triggering of morphogenic change. We suggest that carbon dioxide may be a common effector responsible for the germ tube promoting activity of certain chemical inducers forC.albicans.Key words:Candida albicangerm tubes, CO2-induced germ tube formation, endotrophic germ tube formation.

ISSN:0008-4166    

DOI:10.1139/m90-043

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The total bacterial populations, fluorescent pseudomonads, and actinomycetes in the rhizosphere, rhizoplane, and endorhizosphere of two wheat lines (C-R5B and C-R5D) were investigated weekly during plant growth. The total numbers of bacteria (colony-forming units) were counted on a low-nutrient agar medium, while the numbers of fluorescent pseudomonads and actinomycetes were determined by means of selective media. Fluorescent pseudomonads generally constituted less than 0.5% of the total bacterial numbers and the percentage significantly decreased with time in the rhizosphere, rhizoplane, and root-free soil. The percentages of fluorescent pseudomonads were lower in the rhizoplane than in the rhizosphere, and in the endorhizosphere they were barely detectable. The rapid decline of fluorescent pseudomonads frequently observed in survival studies may be explained by the inability of the plant to support this group of bacteria during later development of its rhizosphere. Actinomycetes generally represented no more than 7% of the total bacterial numbers. Actinomycete percentages were highest in the rhizosphere and root-free soil and lowest in the endorhizosphere. Only minor differences were found in total bacterial numbers and in the numbers of fluorescent pseudomonads between the two wheat lines. However, numbers of actinomycetes were significantly different over the whole experiment between wheat line C-R5B and C-R5D in the rhizosphere, rhizoplane, and endorhizosphere.Key words: actinomycetes, bacteria, fluorescent pseudomonads, rhizosphere, sampling time.

ISSN:0008-4166    

DOI:10.1139/m90-044

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

It is becoming clear that the activity of the hydrogenase enzyme may be involved in the anaerobic biocorrosion of metal, particularly mild steel. Since all hydrogenases appear to be active in the reversible activation of the hydrogen molecule, hydrogenase fromClostridium pasteurianumwas used as a test enzyme for investigating the role of cell-free hydrogenase in anaerobic biocorrosion of mild steel. Evidence is presented which demonstrates the activity of the hydrogenase enzyme in catalyzing removal of cathodically produced hydrogen from mild steel in the presence of the appropriate electron acceptors. The results from the experiments imply that dead cells may also provide, by virtue of their biochemical makeup, all the necessary ingredients to catalyze corrosion of mild steel.Key words: hydrogenase, biocorrosion,Clostridium pasteurianum, iron phosphate complex, cathodic depolarization.

ISSN:0008-4166    

DOI:10.1139/m90-045

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The association of winter wheat (Triticum aestivumL. cv. Norstar) with root-colonizing bacteria (rhizobacteria) was studied in potted soil experiments in the growth chamber. Thirty-six known bacteria, some of which have been reported to stimulate plant growth, and 75 isolates obtained from the rhizosphere of winter wheat were tested for their effects on plant growth and development in two different soils. Two known bacteria and 12 isolates stimulated growth of winter wheat. Of these, the most effective were nine isolates that significantly (P < 0.01) increased plant height, root and shoot biomass, and number of tillers. The plant growth promoting effects of isolates were different in the two soils. Three of these strains were tentatively classified asPseudomonas aeruginosa, and two each asPseudomonas cepacia,Pseudomonas fluorescens, andPseudomonas putida. Some isolates induced significant increases in seedling emergence rates and (or) demonstrated antagonismin vitroagainstRhizoctonia solaniandLeptosphaeria maculans. These results demonstrate the potential use of plant growth promoting rhizobacteria as inoculants for winter wheat.Key words: pseudomonads, plant growth promoting rhizobacteria, winter wheat, rhizosphere, bacterial inoculants.

ISSN:0008-4166    

DOI:10.1139/m90-046

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Complete oxidation of ammonia nitrogen (~1000 mg/L) to nitrite was observed in stabilized swine waste after 49 days in incubation at 400 rpm and 29 °C, only if 10% (v/v) activated sludge from a wastewater treatment unit and 1.5% (w/v) CaCO3, were added. Stabilized swine waste contains less than 0.09 most probable number (MPN) per millilitre of nitrosobacteria and 2.3 MPN/mL of nitrobacteria. In activated sludge, the concentrations of these bacteria were 2.4 MPN/mL for nitrosobacteria and 4.2 × 105 MPN/mL for nitrobacteria. In the swine waste where ammonia was oxidized to nitrite, the nitrosobacteria growth increased to 5.5 × 105 MPN/mL, while the nitrobacteria growth decreased to 2.3 MPN/mL. Inoculation of a freshly stabilized swine waste with 10% (v/v) of the active nitrifying waste and addition of 1.5% (w/v) CaCO3, accelerated the oxidation of ammonia nitrogen to nitrite; the reaction was completed after only 5 days of incubation. Increasing the incubation period to 10 days resulted in the complete oxidation of the accumulated nitrite to nitrate. In the stabilized swine waste, complete nitrification without accumulation of nitrite was obtained in only 5 days of incubation when the waste was inoculated with both enriched nitrifying populations (106–107 MPN/mL).Key words: nitrifying microorganisms, swine waste, nitrification, most probable number.

ISSN:0008-4166    

DOI:10.1139/m90-047

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Population dynamics ofStreptomycesspp. producing melanoid pigments were monitored in field plots planted to the potato cultivars 'Chippewa' (susceptible to common scab) or 'Superior' (resistant), and in fallow control plots. Relative frequencies of streptomycetes most commonly isolated from soil, the rhizosphere, and potato tuber surfaces were determined during two growing seasons. Shannon indices of diversity indicated populations in soils planted to potatoes were more diverse than populations in fallow soil. In 1986,S.diastatochromogenesandS.longisporusaccounted for ≥38% of all streptomycetes observed in all three environments. In 1987,S.diastatochromogeneswas observed frequently in soil, whileS.longisporuswas observed rarely in all environments. Relative numbers of threeStreptomycesspp. differed in the rhizospheres of 'Chippewa' and 'Superior' (P ≤ 0.05). This is the first report of a differential response ofStreptomycesspp. to potato cultivars.Key words: rhizosphere,Solanum tuberosum,Streptomycesspp., melanin.

ISSN:0008-4166    

DOI:10.1139/m90-048

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Growth factors forBifidobacterium bifidumwere detected in faeces of axenic mice strain C3H. Most of these factors were found in the nondialyzable fraction obtained after aqueous extraction and dialysis. SDS–PAGE and filtration chromatography on Sepharose 4B revealed that many glycosylated components harbored a bifidigenic activity. Intestinal colinization of mice byB.bifiduminvolved the utilization and eventually the disappearance of the intestinal bifidigenic factors. There was no change in the protein concentration in fecal extracts, but the total hexose concentration was lower. Comparison of electrophoretic PAGE profiles after periodic acid Schiff coloration showed that bacteria used up the glycosylated fractions of many glycopeptides, particularly those of mucins and four glycoproteins. There was no correlation between the hexose concentration detected in every active fraction and the degree ofin vivodegradation of bifidigenic factors. The attack on active glycopeptides having a molecular mass greater than 670 kDa thus revealed hexose sites that were not detectable previously by the phenol – sulfuric acid method. However, the amount of bifidigenic factors detectedin vitroallowed us to measure the importance of the degradation of a component byB.bifidum in vivo.Key words:Bifidobacterium, bifidigenic factors, intestinal mucus, axenic mice. [Journal translation]

ISSN:0008-4166    

DOI:10.1139/m90-049

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The isotypic immune response of 16 individuals who developed Q fever pneumonia following exposure to an infected parturient cat was studied. The enzyme-linked immunosorbent (ELISA) test was used to detect IgM, IgA, and IgG antibodies to phase I and phase IICoxiella burnetiiwhole-cell antigens and to the phase I lipopolysaccharide. The indirect immunofluorescent antibody (IFA) test was also used to detect antibodies to phase I and phase II whole cells. None of the 16 subjects developed antibodies to the phase I lipopoly saccharide. The ELISA was more sensitive than the IFA test. IgM antibodies to phase II antigen were detectable by ELISA in 80% of the subjects at the time of onset of symptoms and were still present in 7 of the 8 tested at 32 weeks following the onset of symptoms. In all instances (ELISA: IgG, IgM; IFA: IgG, IgM) phase II antibodies developed earlier and reached higher levels than did phase I antibodies. The absence of antibodies to phase I lipopolysaccharide in acute Q fever combined with our unpublished findings of antibodies to phase I lipopoly saccharide in chronic Q fever suggests that this test may be used to distinguish acute from chronic Q fever.Key words: Q fever, immune response, ELISA.

ISSN:0008-4166    

DOI:10.1139/m90-050

出版商:NRC Research Press    

年代:1990

数据来源: NRC