摘要:

Endolithic microbial communities dominated by photosynthetic cyanobacteria occur at a depth of 0.5 – 3.0 mm inside dolomitic limestone that forms the vertical cliffs of the Niagara Escarpment in Ontario, Canada. CoccoidGloeocapsawas the most prominent cyanobacterial species in colonized rock samples examined by differential interference contrast and episcopic fluorescent microscopy. Filamentous varieties of cyanobacteria were less common than coccoid forms but could be easily distinguished in all slide mount preparations. Scanning electron microscopy showed that the endoliths occurred in communal populations situated within the open pore spaces of the limestone. Heterotrophic bacteria were also observed growing as epiphytes on dead and living cyanobacteria, and in epilithic biofilms on pore space walls. In thin-sectioned specimens examined by transmission electron microscopy, these adherent bacteria commonly exhibited extensive accumulations of fibrous extracellular polymeric materials external to their cell walls. Biomass concentrations, estimated from the organic phosphorus content of the samples, generally paralleled rock porosity and ranged from 3.3 to 17.1% dry weight. Carbon isotope (14C) measurements indicated that atmospheric carbon dioxide is used by the endolithic cyanobacteria, rather than dissolved inorganic carbon from the weathering of carbonate minerals in the limestone host rock. In addition, whole rock multielement analyses revealed an enrichment of some elements (e.g., phosphorus, barium, lead, and zinc) in the endolith zone over the host rock, while other elements (e.g., magnesium, calcium, iron, and copper) were depleted. The implication is that the endolithic microorganisms play an active role in the biogeochemical cycling of nutrient and trace elements in cliff face ecosystems of the Niagara Escarpment.Key words: limestone, endolith, biofilm, cyanobacteria, geochemistry.

ISSN:0008-4166    

DOI:10.1139/m97-029

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

A 3.1-kb region of the bacteriophage D3 genome which contains the immunity functions has recently been sequenced (GenBank accession No. L22692). Sequence analysis indicated the presence of a putative repressor gene (c1) whose protein product functions to maintain the bacteriophage genome as a stably integrated prophage in the chromosome ofPseudomonas aeruginosa. A plasmid was constructed that overexpresses repressor C1 protein under control of PtacinEscherichia coli. C1 protein was subsequently purified and characterized as a 223 amino acid protein with specific binding affinity for 14-base imperfect palindromic operator sequences located on the genome of bacteriophage D3. N-terminal protein sequence data obtained from automated Edman degradation (16 cycles) of purified repressor protein were identical to the predicted sequence based on DNA sequence analysis of thec1open reading frame.Key words: promoter, repressor, operator, lambdoid phage,Pseudomonas aeruginosa.

ISSN:0008-4166    

DOI:10.1139/m97-030

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

The plant pathogenic fungusVerticillium dahliaeproduced extracellular alkaline protease activity when grown in liquid medium supplemented with a protein source. A serine protease was purified 80-fold in a single step, using cation-exchange chromatography, from the filtrate of cultures grown with skim milk as a protein source. N-terminal amino acid sequence analysis of the 30-kDa protein (VDP30) that copurified with the serine protease activity suggested that VDP30 is a trypsin-like protein. The purified enzyme hydrolyzed the synthetic substrateNα-benzoyl-DL-argininep-nitroanilide hydrochloride (BAPNA), and the activity on BAPNA was inhibited by leupeptin, further verifying the trypsin-like nature of the enzyme.Key words: proteinase, phytopathogen, verticillium wilt, wilt fungi.

ISSN:0008-4166    

DOI:10.1139/m97-031

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Routine serosubtyping ofNeisseria meningitidisrelies upon reactivity of whole cells to monoclonal antibodies (mAbs). This procedure is limited in providing maximum serosubtype information because some epitopes in whole cells are masked and because mAbs are currently unavailable for some epitopes. To address masking of epitopes in whole cells, we isolated outer membrane vesicles (OMVs) from nine representative meningococcal strains that were isolated (1991–1993) in the province of Quebec, Canada; the OMVs were used in enzyme-linked immunosorbent assay for reactivity to mAbs, and improved serosubtyping information was obtained. A recent proposal assigns subtypes based on deduced amino acid sequences in the variable regions of the class 1 outer membrane protein. This scheme maintains the subtyping nomenclature that is based on reactivity to mAbs by defining the sequences in the epitopes recognized by the mAbs. We used this technique to assign subtypes to the meningococcal strains isolated in Quebec. For the strains tested, serosubtyping using mAbs and subtyping based on deduced amino acid sequences were in complete agreement. Subtyping using deduced amino acid sequences is superior because it does not depend on the availability of mAbs.Key words:Neisseria meningitidis, outer membrane proteins, serosubtyping, PorA.

ISSN:0008-4166    

DOI:10.1139/m97-032

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

The promoter activity of anAcanthamoebapolyubiquitin gene was analyzed in its homologous system. A modified calcium phosphate transfection method using a neomycin marker vector was developed to achieve highly efficient transfection of theAcanthamoebapolyubiquitin gene intoAcanthamoebacells. In this transfection procedure, the calcium phosphate – DNA complex was formed gradually in the medium during incubation with cells and precipitated on the cells. The crucial factors for obtaining efficient transfection were the pH (6.95) of the transfection buffer used for the calcium phosphate precipitation and the amount (25 μg/96-well tissue culture plate) and form (circular) of transfecting DNA. Under these conditions,Acanthamoebaisolate 1B6 was transfected at an efficiency of about 40% with the constructed vector pOPSBU, a pOP13CAT-based polyubiquitin gene incorporated neomycin resistance vector.Acanthamoeba polyphagawas transfected at an efficiency of about 10% with this vector. Transfection of bothAcanthamoebastrains appeared to result in low copy plasmid integration (about two copies per cell are suggested). The chloramphenicol acetyltransferase (CAT) assays showed that the promoter of theAcanthamoebapolyubiquitin gene in the constructed vector was especially strong inA.polyphaga, thus the pOPSBU –Acanthamoebasystem may be useful for the construction of cDNA expression libraries, as well as for the expression of cloned genes.Key words:Acanthamoeba, transfection, ubiquitin, promoter, vector, CAT assay.

ISSN:0008-4166    

DOI:10.1139/m97-033

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

The r2 isolate ofFusarium oxysporumf.sp.radicis-lycopersiciproduced several pectic enzymes that differ in substrate preference, reaction mechanism, and action pattern. We detected three forms that have lyase activity, four forms with polygalacturonase activity and one form with pectinesterase activity. Lyases had an absolute requirement for calcium and pIs of 9.20, 9.00, and 8.65. The two more alkaline forms had a weak preference for pectin, whereas the other was more active on polygalacturonate. Polygalacturonases had pIs of 9.30, 7.35, 6.85, and 6.55 and were inhibited by calcium ions. Lyases and polygalacturonases were induced by galacturonic acid and were subject to catabolite repression. Induced synthesis occurred at pHs 5.5 and 8.0 and no increase in lyase activities were promoted by alkalinization of cultures. Pectin lyase had an endo mode of action, whereas pectate lyase and polygalacturonase behaved more as exoenzymes. These results are discussed in relation to the appearance of the different pectic enzymes when the fungus is confronted with a pectic polymer.Key words:Fusarium oxysporumf.sp.radicis-lycopersici,Lycopersicon esculentum, pectate lyase, pectin lyase, polygalacturonase.

ISSN:0008-4166    

DOI:10.1139/m97-034

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Investigations were conducted to determine if biological control agentPseudomonas fluorescens89B-61 could colonize cotton tissues systemically and if internal colonization by a known endophytic bacterium,Enterobacter asburiaeJM22, was influenced by the presence of other plant-associated bacteria. Following seed treatment,Pseudomonas fluorescens89B-61 colonized cotton roots both externally and internally at mean population densities of 8.7 × 105 CFU/g and 1.1 × 103 CFU/g, respectively. However, bacteria were not detected in cotyledons, leaves, or stems. After inoculation onto leaves,Pseudomonas fluorescens89B-61 established a mean internal population density of 1.6 × 104 CFU/g leaf tissue. Following stem injection,Pseudomonas fluorescens89B-61 did not colonize roots or leaves.Pseudomonas fluorescens89B-61 was localized on the root surface concentrated in grooves between epidermal cells, below collapsed epidermal cells, and in intercellular spaces close to the root epidermis, as identified by immunogold labeling of the bacterial membrane. Combined application ofE.asburiaeJM22 with another endophyte,Paenibacillus maceransTri2-10, resulted in significantly lower internal populations ofE.asburiaeJM22 compared with treatment withE. asburiaeJM22 alone. However, when coinoculated with a rhizosphere colonist,Micrococcus agilisstrain 2RD-11, the colonization density ofE.asburiaeJM22 was not negatively affected. The results suggest that the internal colonization of cotton by bacteria with biological control activity may be an important aspect in their capacity to protect host plants against plant pathogens. The extent of internal colonization was shown to be influenced by other bacterial colonists.Key words: endophytic bacteria, location, interaction, cotton.

ISSN:0008-4166    

DOI:10.1139/m97-035

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Downy mildew of sunflower (Helianthus annuusL.) incitated byPlasmopara halstediiis a potentially devastating disease. We report here the finding of two new races ofP.halstediiand also two Apron35S fungicide-resistant isolates of race A. Using the random amplified polymorphic DNA (RAPD) technique as an initial screening for genetic variation withinP.halstediiFrench races, genetic variation was not found between isolates within races 1, A, or B, and very few polymorphisms were distinguished between all French races known today.Key words:Plasmopara halstedii, race, genetic variability, RAPD.

ISSN:0008-4166    

DOI:10.1139/m97-036

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

The microbial oxidation of hydrogen sulphide present in an air stream was performed using a laboratory-scale biofilter packed with dry wastewater sludge (BSE, boues de station d'épuration) from an urban wastewater treatment plant. This granular and heterogeneous material contains organic and mineral components which favour colonization by bacteria. Adsorption and absorption of hydrogen sulphide taking place on such a packing (moisture content 30–40%) were determined. Results obtained with abiotic pilot units, fed with air (superficial air flow rate, 16 m/h) containing a sulphide level as high as 3260 mg/m3, showed that chemical oxidation can occur. The presence of numerous bacteria such asThiobacillusspp. (i.e., 108–109 CFU/g dry weight) in biotic pilot units favoured complete oxidation to sulphate. High initial bacterial numbers and a neutral pH improved the removal efficiency of the biofilter. A high sulphide concentration (>3000 mg/m3) had a negative effect on the removal efficiency. The leaching of the metals contained in the sludges was studied. Peat and BSE biofilters were compared.Key words:Thiobacillusspp., hydrogen sulphide, biofilter, deodorization, bioleaching.

ISSN:0008-4166    

DOI:10.1139/m97-037

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

The microbial characteristics of deep granitic nutrient-poor groundwater from two boreholes at the Underground Research Laboratory of Atomic Energy of Canada Limited were studied. Scanning electron microscopy of the groundwater samples revealed significant numbers of bacteria of various sizes and shapes, including spherical, rod, and curved shaped. A few bacteria with appendages were also observed. Significant numbers of bacteria (~105/mL) were enumerated using acridine orange (AO) staining. An active microbial population was detected with three direct methods and it ranged from 1 to 83% of the AO count, depending on the method used. Culturable aerobic and anaerobic (including facultative) heterotrophic bacteria ranged from 0.06 to 10.2% and 0.008 to 7.35%, respectively, of the AO count. Denitrifying, N2-fixing, sulphate-reducing, and iron-precipitating bacteria were present, but no iron-oxidizing bacteria or methanogens could be detected. Tentative identification of 160 isolates using the Biolog® system showed a predominance of threePseudomonasspecies,P.fluorescens,P.marginalis, andP.corrugata. Phospholipid fatty acid analysis showed that the bacteria in the groundwater samples faced starvation stress. However, laboratory studies showed that these bacteria can efficiently uptake and mineralize organic substrates when supplied.Key words: deep groundwater, microbial communities, characterization.

ISSN:0008-4166    

DOI:10.1139/m97-038

出版商:NRC Research Press    

年代:1997

数据来源: NRC