摘要:

Efficient selection of fungi for biological control of nematodes requires a series of screening assays. Assessment of genetic diversity in the candidate species maximizes the variety of the isolates tested and permits the assignment of a particular genotype with high nematophagous potential using a rapid novel assay. Molecular analyses also facilitate separation between isolates, allowing the identification of proprietary strains and trace biocontrol strains in the environment. The resistance of propagules to UV radiation is an important factor in the survival of a biocontrol agent. We have analyzed 15 strains of the nematophagous fungusPaecilomyces lilacinususing these principles. Arbitrarily primed DNA and allozyme assays were applied to place the isolates into genetic clusters, and demonstrated that some genetically relatedP. lilacinusstrains exhibit widespread geographic distributions. When exposed to UV radiation, some weakly nematophagous strains were generally more susceptible than effective isolates. A microtitre tray-based assay used to screen the pathogenic activity of each isolate toMeloidogyne javanicaegg masses revealed that the nematophagous ability varied between 37%-100%. However, there was no clear relationship between nematophagous ability and genetic clusters. Molecular characterizations revealed sufficient diversity to allow tracking of strains released into the environment.Key words:Paecilomyces lilacinus, LP-RAPD analysis, allozymes, UV sensitivity.

ISSN:0008-4166    

DOI:10.1139/w00-062

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

In this work, the establishment of material balances and stoichiometry of the growth ofBacillussp. was undertaken. This strain produces high quantities of a xylanase suitable for use as bleach boost agent in chlorine-free bleaching sequences of paper pulp. As carbon dioxide plays an important role as a growth factor, bacterial growth in two fermentations, one fed with air and another fed with carbon-dioxide-enriched air, were compared. For this purpose, a method permitting the determination of the consumption of the two carbon sources, xylan and peptone, was proposed. The material balances revealed that in both cases, the bacteria first use peptone as their carbon source, and then xylan in the second part of the growth phase. The aerated culture showed diauxic growth on these two substrates, whereas carbon-dioxide-enriched air caused disappearance of the metabolic adaptation phase, and rendered biomass production more economic. The fermentation fed with air needed 30% more xylan than the fermentation fed with carbon-dioxide-enriched air for the same quantity of biomass produced.Key words:Bacillussp., carbon dioxide, material balances, diauxic growth.

ISSN:0008-4166    

DOI:10.1139/w00-064

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The mycorrhizal relationships between pines and two edible species ofLactariussect.Dapeteswere investigated by optimizing the experimental conditions of mycelial growth and of mycorrhizal colonization of pine seedlings. In vitro mycelial growth ofLactarius deliciosusandL. sanguifluuswas improved on a buffered medium containing glucose, amino acids, and vitamins. Two methods of mycorrhization of pines withLactarius deliciosuswere tested. The mycorrhizal colonization was rapid and intense under non-aseptic conditions with a low nutrient supply and without exogenous glucose. A positive influence of mycorrhizal colonization onPinus sylvestrisgrowth was subsequently observed. Under axenic conditions and with a high nutrient supply, mycorrhization was stimulated at 10 g/L of exogenous glucose, irrespective of the phosphorus concentration. At high phosphorus level (1 mM) and 0.1, 1.0, or 10.0 g/L glucose, growth ofPinus sylvestriswas reduced by inoculation. Stability and development ofPinusspp./Lactarius deliciosussymbioses were assayed in a climatic chamber using containers filled with a synthetic substrate. Over a 2-year culture period, the root systems of the pine seedlings were heavily colonized byLactarius deliciosus. One year following inoculation,Lactarius deliciosusfruit-body primordia appeared associated withPinus sylvestrisseedlings. Six months later, two mature basidiomata were obtained. This is the first report of soilless fruit-body formation of this edible mushroom.Key words: ectomycorrhiza, inoculation,Lactarius deliciosus,Lactarius sanguifluus,Pinus, wild edible mushrooms.

ISSN:0008-4166    

DOI:10.1139/w00-059

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Pathogenic and nonpathogenic isolates ofVenturia inaequaliswere grown in liquid culture. Hyphae were treated with two types of fimbrial antiserum (AU- and AV-1) and examined by immunofluorescent microscopy, in order to establish the distribution of fimbrial epitopes in whole cell mounts. The AV-1 antiserum was specific for the glycoprotein subunits while the AU- antiserum was specific for the protein moieties present on the fimbriae ofMycobotryum violaceum. The use of fimbrial antiserum with immunocytochemistry and transmission electron microscopy demonstrated a clear distinction between pathogenic and nonpathogenic isolates ofV. inaequalis, based on the appearance of the fungal cell wall and the distribution of fimbrial epitopes labeled with AV-1 antiserum and immunogold complex. In actively growing hyphae of the pathogenic isolate, characterized by distinct cellular organelles, small vacuoles, and lipid bodies, fimbrial epitopes were concentrated in the fungal cell wall and were present minimally on the outer surface. In contrast, actively growing hyphae of the nonpathogenic isolate ofV. inaequalishad extensive fine hair-like protrusions in the fungal cell wall which labeled with the AV-1 antiserum and immunogold. The distribution of fimbrial epitopes inV. inaequaliswas highly dependent on the developmental growth stage of the fungal mycelium. Aging mycelia in both the pathogenic and nonpathogenic isolates ofV. inaequaliswere characterized by a large central vacuole and no label. In the pathogenic and nonpathogenic isolates ofV. inaequalisgrown in vitro, the distribution of fimbrial glycoprotein epitopes provided a more complex profile than that seen inM. violaceum.Key words: fimbriae, immunocytochemistry,Venturia inaequalis,Mycobotryum violaceum.

ISSN:0008-4166    

DOI:10.1139/w00-061

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The effect of various carrier formulations ofBacillus subtilisandPseudomonas putidawere tested on germination, growth, and yield of lettuce and cucumber crops in the presence ofPythium aphanidermatumandFusarium oxysporumf.sp.cucurbitacearum, respectively. Survival ofB. subtilisandP. putidain various carriers under refrigeration (about 0°C) and at room temperature (about 22°C) was also studied. In all carrier formulations,B. subtilisstrain BACT-0 survived up to 45 days. After 45 days of storage at room temperature (about 22°C), populationsB. subtilisstrain BACT-0 were significantly higher in vermiculite, kaolin, and bacterial broth carriers compared with other carriers. Populations ofP. putidawere significantly higher in vermiculite, peat moss, wheat bran, and bacterial broth than in other carriers when stored either under refrigeration (about 0°C) or at room temperature (about 22°C) for 15 or 45 days. Germination of lettuce seed was not affected in vermiculite, talc, kaolin, and peat moss carriers, but germination was significantly reduced in alginate and bacterial broth carriers ofB. subtiliscompared to the non-treated control. Germination of cucumber seed was not affected by any of the carriers. Significantly higher fresh lettuce and root weights were observed in vermiculite and kaolin carriers ofB. subtiliscompared withP. aphanidermatum-inoculated control plants. Lettuce treated with vermiculite, and kaolin carriers ofB. subtilis, or non-inoculated control lettuce plants had significantly lower root rot ratings than talc, peat moss, bacterial broth, andP. aphanidermatum-inoculated control plants. Growth and yield of cucumber plants were significantly higher in vermiculite-based carrier ofP. putidathan the other carriers andFusarium oxysporumf.sp.cucurbitacearum-inoculated plants.Key words:Bacillus subtilis, Pseudomonas putida,Fusariumoxysporumf.sp.cucurbitacearum,Pythium aphanidermatum, talc, vermiculite, alginate, kaolin, peat moss, wheat bran, oat

ISSN:0008-4166    

DOI:10.1139/w00-063

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Mushroom compost manufacturers in Ireland are moving away from the traditional outdoor phase I windrow method, favouring in-vessel production. Composters and growers have reported better quality compost with faster spawn run and higher yields produced by this process. In the present study, physical examination of samples highlighted differences when comparing the windrow and in-vessel methods of compost production. Observations using scanning electron microscopy suggest that the cuticle of wheat straw from in-vessel production is damaged during phase I, peeling away from the surface in fragments, and exposing the epidermis. Changes in silicon levels on the straw surface acted as a marker for cuticle damage when comparing both composting systems. Cuticle damage may be important during composting and afterwards, as substrate colonisation is faster, and consequently spawn run is shorter. The phase I compost microbial community is altered by the in-vessel technique, producing a predominantly thermophilic bacterial flora in contrast to the mesophilic and thermophilic bacteria and fungi found in windrow phase I compost. These differences may be significant in mushroom compost production.Key words: windrow, in-vessel, compost, cuticle, straw.

ISSN:0008-4166    

DOI:10.1139/w00-058

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

In this report we show that fast-growing non-pathogenic mycobacteria degrade cholesterol from liquid media, and are able to grow on cholesterol as a sole carbon source. In contrast, slow-growing mycobacteria, including pathogenicMycobacterium tuberculosisand bacillus Calmette-Guérin (BCG), do not degrade and use cholesterol as a carbon source. Nevertheless, pathogenic mycobacteria are able to uptake, modify, and accumulate cholesterol from liquid growth media, and form a zone of clearance around a colony when plated on solid media containing cholesterol. These data suggest that cholesterol may have a role in mycobacterial infection other than its use as carbon source.Key words: mycobacteria, cholesterol, biodegradation

ISSN:0008-4166    

DOI:10.1139/w00-060

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

A macrorestriction map of the genome ofMycoplasma hyopneumoniaestrain J, the type strain of the causative agent of enzootic pneumonia in pigs, was constructed using pulsed-field gel electrophoresis (PFGE) and DNA hybridization. The size of the genome as determined by PFGE was approximately 1070 kb. Assembly of theM. hyopneumoniaegenomic map was facilitated and complimented by the simultaneous construction of an ordered cosmid library. Five contigs of overlapping cosmids were assembled, which together represent coverage of approximately 728 kb. Forty-two genetic markers (including three types of repeated elements) were placed on theM. hyopneumoniaemap. Closer examination of anApaI restriction fragment contained entirely within a single cosmid insert suggests that the genome size may be overestimated by PFGE.Key words:Mycoplasma hyopneumoniae, mollicutes, physical map, genetic map.

ISSN:0008-4166    

DOI:10.1139/w00-069

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Under normal cultivation conditions, a mixture of turbid and clear plaques is often apparent in cultures of bacterial cells infected with filamentous bacteriophages. Beginning with a culture of wild-type filamentous phage f1, which itself produces turbid plaques, a clear plaque strain (c1) was isolated. From c1, the turbid plaque strain t1 was isolated; from t1, the clear plaque strain c2 was isolated; and from c2, the turbid plaque strain t2 was isolated. Each of these strains was generated with a frequency of approximately 1 × 10-4. Although filamentous phages have been thought not to induce host cell death, both turbid and clear plaque strains of f1 killed host bacteria. Plating of bacterial cells 1 h after infection revealed that colonies produced by cells infected with either wild-type f1 or strain c2 were smaller than those derived from uninfected cells, and that colony formation by infected cells was reduced by 15% and 38%, respectively. The time course of bacterial growth revealed that, at 4 h after infection, the number of CFU per milliliter of culture of cells infected with wild-type f1 or with strain c2 was reduced by 27% and 95%, respectively, compared with that for uninfected cells. Microculture analysis also revealed that the percentages of nondividing cells in f1 or c2 infected were 19% and 52%, respectively, 4 h after infection with wild-type f1 or with strain c2; no such cells were detected in cultures of uninfected cells. Negative staining and electron microscopy showed that 20% and 61% of cells infected with wild-type f1 or with strain c2 were dead 4 h postinfection. Finally, although the rates of DNA synthesis were similar for infected and uninfected cells, the rates of RNA and protein synthesis were markedly reduced in infected cells.Key words:Escherichia coli, bacteriophages, turbid plaque, clear plaque

ISSN:0008-4166    

DOI:10.1139/w00-068

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The physically linkedhisGandhisEgenes, encoding for ATP-phosphoribosyltransferase and phosphoribosyl-ATP-pyrophosphohydrolase were isolated from theCorynebacterium glutamicumgene library by complementation ofEscherichia colihistidine auxotrophs. They are two of the nine genes that participate in the histidine biosynthetic pathway. Molecular genetics and sequencing analysis of the cloned 9-kb insert DNA showed that it carries thehisGandhisEgenes. In combining this result with our previous report, we propose that all histidine biosynthetic genes are separated on the genome by three unlinked loci. The coding regions of thehisGandhisEgenes are 279 and 87 amino acids in length with a predicted size of about 30 and 10 kDa, respectively. Computer analysis revealed that the amino acid sequences of thehisGandhisEgene products were similar to those of other bacteria.

ISSN:0008-4166    

DOI:10.1139/w00-065

出版商:NRC Research Press    

年代:2000

数据来源: NRC