摘要:

Helicobacter pyloriis present in 40-60% of the population and approximately 10-20% of these infected individuals suffer from aH. pyloriassociated disease such as peptic ulcer disease or gastric cancer. This article reviews the potential bacterial determinants responsible for and markers predictive of both the acquisition ofH. pyloriinfection and subsequent clinical outcome; i.e., asymptomatic infection or disease. The acquisition ofH. pyloriinfection depends on exposure (hence the increased risk in lower socioeconomic groups and developing nations) to viable bacteria with at least a functional urease gene in a susceptible host. Once infection occurs, bacterial virulence factors, including the vacuolating cytotoxin, and genes of the cag pathogenicity island, as well as nonbacterial factors may determine disease outcome. Future research is being directed at discovering other bacterial virulence factors responsible for the different clinical outcomes ofH. pyloriinfection. This will be greatly enhanced by the recent release of the complete genome sequence ofH. pylori. The determination of the relative importance of each of these recognized and other as yet unrecognized factors responsible for disease outcome will assist in the appropriate targeting of patients in the treatment ofH. pyloriinfection.Key words:Helicobacter pylori, genetics, virulence, bacterial.

ISSN:0008-4166    

DOI:10.1139/w97-143

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

In situ mesocosm experiments were performed in Lake Schwelvollert (located in the district of Weißenfels, Saxony-Anhalt, Germany), an anaerobic lignite-carbonization effluent lake containing phenolic compounds and their autoxidation products (anthropogenic humic matter). In the aeration enclosure, the anaerobic Schwelvollert wastewater was aerated and in the flocculation enclosure, it was flocculated to precipitate the oxygen-trapping anthropogenic humic matter to enhance the input of oxygen by diffusion. To gain an insight into the metabolic state of the aerobic heterotrophic microbiota during the treatments, arbitrary samples of bacterial isolates were taken from a general agar medium and tested for their abilities to cleave predominant phenolic contaminants by a procedure called the isolate sample assay. In this way, successions of degradation potentials were observed in both mesocosms, with degradation abilities formeta- andpara-alkylated phenols appearing before degradation abilities forortho-substituted phenols as a common phenomenon. To examine the structure of samples, the respective isolates were characterized using the Biolog GN MicroPlate system, the random amplified polymorphic DNA nucleic acid (RAPD) fingerprinting technique, and amplified ribosomal DNA restriction analysis (ARDRA). Although similar functional patterns occurred in both mesocosms, the compositions and diversities of the respective bacterial communities varied significantly, even at different depths from the same enclosure, with members of thePseudomonasRNA group I being predominant.Key words: lignite carbonization, phenols, mesocosm, isolate sample assay, Biolog, RAPD, ARDRA.

ISSN:0008-4166    

DOI:10.1139/w97-151

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The process of infection of carrots byPythium violaeandPythium ultimum, two causes of cavity spot, is described. The first species causes limited root necrosis, the second progressive root rot. Colonization by both species was intracellular and limited within the tissues. Modes of cell wall degradation were studied by staining (PATAg test) and labeling techniques. Pectins were labeled with monoclonal antibodies and cellulose with an exoglucanase-gold complex. Cell wall polysaccharides were degraded differently by the two species.Pythium violaewas responsible for degradations, which could be noticeable, especially for high methylesterified pectins, but which occurred after colonization and were localized near the hyphae. The conservation of integrity of diseased tissue was apparently due to the absence of degradation away from the hyphae. In contrast,P. ultimumwas responsible for more extensive degradation of pectins and cellulose, which occurred at a relatively greater distance from the hyphae. Degradation of pectins was always more rapid in the cell walls than in the intercellular junctions. This phenomenon led to loss of tissue integrity and could explain the tissue maceration caused byP. ultimuminfection. These differences in infection process are discussed in connection with the enzymic potential for degradation of cell wall polysaccharides.Key words:Daucus carotaL.,Pythium, pectin, cellulose, cytochemistry.

ISSN:0008-4166    

DOI:10.1139/w97-157

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Fifteen isolates of fungal endophytes of grasses were studied for their ability to metabolize different sources of carbon and nitrogen. These endophytes had been isolated from 12 different species of Poaceae and included Clavicipitaceae with or without a teleomorph (generaEpichloëandNeotyphodium, respectively) and species belonging to the genusAcremoniumsensu stricto (Acremonium chilense-like). Pectin and cellulose as carbon sources and tryptophan and methionine as nitrogen sources appeared to support poorly the growth of most isolates. Hexoses, disaccharides, complex nitrogen sources, asparagine, and glutamine supported growth of all isolates. The isolates of genusNeotyphodiumwere characterized by limited growth whatever the substrate, the inhibition of their growth by high concentrations of glucose and fructose, and their inability to assimilate pentoses (xylose, arabinose) and nitrates. The isolates of genusEpichloëshowed better growth than those of the previous group and their growth was not inhibited by high concentrations of glucose, but they were also unable to use pentoses. TheAcremonium chilense-like isolates showed rapid growth and were distinguished by their ability to use the pentoses and nitrates. In contrast, they showed relatively poor growth on methionine and alanine as nitrogen sources. They showed the most rapid growth on high concentrations of glucose or fructose.Key words: carbon sources, nitrogen sources,Neotyphodium,Epichloë, Acremonium,grass endophytes.

ISSN:0008-4166    

DOI:10.1139/w98-004

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Glycolipid-producing bacteria were isolated from soil samples. One of the strains, identified asCellulomonas cellulans(Oerskovia xanthineolytica), was found to produce significant amounts of unusual extracellular glycolipids, which were shown to be composed of at least 11 individual compounds. Hydrolysis of the glycolipid mixture and gas chromatography - mass spectrometry analysis revealed the presence of fatty acids and hydroxy fatty acids ranging from C10to C18, 16 of which were identified. The glycidic moiety consisted of glucose, rhamnose, and ribose. The same sugars were found to be present in the cell wall ofCellulomonas cellulans, which also contained polar lipids including glycolipids. During strain cultivation, glycolipid excretion was stimulated when nitrogen was exhausted from the culture medium. In these conditions, the production in fermenters on glycerol, expressed in glucose equivalents, reached 8.9 g/L. Cell hydrophobicity, which rose to 95% during the growth phase, decreased to 50% during the production phase. The overall results show that the bacterial cell wall is involved in the synthesis of these new extracellular glycolipids.Key words: glycolipid, excretion,Cellulomonas cellulans,Oerskovia xanthineolytica, cell wall.

ISSN:0008-4166    

DOI:10.1139/w97-156

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

In vitro adherence assays were used to determine whether the S layer mediated interactions betweenCampylobacter fetussubsp.venerealisstrains and HEp-2 cells. At multiplicity of infection ratios ranging from 0.1:1 through 100:1, quantitation of bacterial adherence by light microscopy revealed that S layer deficient isogenicC. fetus809K andC. fetus810K were not less efficient in their attachment to HEp-2 cells; either S layer deficientC. fetusstrains interacted with HEp-2 cells in greater numbers than the corresponding wild-type parent strains 809 and 810 or there was no significant difference in adherence levels between wild-type and mutant strains. Adherence ofC. fetusstrains to HEp-2 cells increased most during the first 2 h of a 22-h incubation period with only a slight increase inC. fetuscell numbers occuring subsequent to 2 h. At each assay point throughout this 22-h time period, equivalent numbers of wild-type and S layer deficientC. fetusstrains were observed associated with HEp-2 cells. Prior to 2 h, adherence levels of allC. fetusstrains exceeded those ofEscherichia coliAB264 andSalmonella typhimuriumSL1344. And, unlikeS. typhimurium,C. fetusdid not undergo significant replication following initial adherence to HEp-2 cells.Campylobacter fetusdid not adhere to HEp-2 cells in a localized or aggregative pattern but were randomly distributed over individual HEp-2 cells and at no time during the assay withC. fetuswere changes in HEp-2 cell morphology apparent. These data suggest that the S layer is not essential for mediating initial interactions betweenC. fetusand HEp-2 cells.Key words:Campylobacter fetus, S layer, HEp-2.

ISSN:0008-4166    

DOI:10.1139/w97-153

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Bacteria belonging to the familyVibrionaceaewere suspended using saline and a solution prepared from a marine-cations supplement. The effect of this on the profile of oxidized substrates obtained when using Biolog GN MicroPlatesTMwas investigated. Thirty-nine species belonging to the generaAeromonas, Listonella, Photobacterium,andVibriowere studied.Of the strains studied, species ofListonella, Photobacterium,andVibriocould be expected to benefit from a marine-cations supplement that contained Na+, K+, and Mg2+. Bacteria that are not of marine origin are usually suspended in normal saline. Of the 39 species examined, 9 were not included in the Biolog data base and were not identified. Of the 30 remaining species, 50% were identified correctly using either of the suspending solutions. A further 20% were correctly identified only when suspended in saline. Three species, or 10%, were correctly identified only after suspension in the marine-cations supplemented solution. The remaining 20% of species were not correctly identified by either method. Generally, more substrates were oxidized when the bacteria had been suspended in the more complex salts solution. Usually, when identifications were incorrect, the use of the marine-cations supplemented suspending solution had resulted in many more substrates being oxidized. Based on these results, it would be preferable to use saline to suspend the cells when using Biolog for identification of species ofVibrionaceae. A salts solution containing a marine-cations supplement would be preferable for environmental studies where the objective is to determine profiles of substrates that the bacteria have the potential to oxidize. If identifications are done using marine-cations supplemented suspending solution, it would be advisable to include reference cultures to determine the effect of the supplement. Of theVibrioandListonellaspecies associated with human clinical specimens, 8 out of the 11 studied were identified correctly when either of the suspending solutions was used.Key words: Biolog, cations, salts, marine bacteria,Vibrionaceae.

ISSN:0008-4166    

DOI:10.1139/w97-150

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The &dgr; -endotoxin genes fromBacillus thuringiensiswere introduced into a rhizosphere-inhabitingBacillus pumilusisolate to create a &dgr; -endotoxin expression and delivery system for subterranean feeding insects such as the larvae of pale western cutworm (Agrotis orthogoniaMorrison (Lepidoptera: Noctuidae)). Preliminary experiments indicated thatBacillus thuringiensissubsp.kurstakicultures were toxic to pale western cutworm larvae. Three differentcrygenes fromBacillus thuringiensissubsp.kurstakiwere cloned into high and low copy number vectors and mated intoBacillus pumilusRB8. When carried on high copy number vectors,crygenes appeared to inhibit sporulation and &dgr; -endotoxin production inBacillus pumilusRB8 cultures, since microscopic examination of these cultures revealed that <0.1% of the cells of late stationary phase cultures had sporulated and produced parasporal inclusions. On low copy number vectors, thecrygenes did not inhibit sporulation; however, production of &dgr; -endotoxins was undetectable. Using a heat shock regime for enrichment of sporogenous crystalliferous variants, aBacillus pumilusisolate, carryingcryIA(c) on a high copy number plasmid, was obtained in which high level &dgr; -endotoxin production occurred concomitant with sporulation. Synthesis of functional &dgr; -endotoxin by this strain was confirmed by Western blot analysis and bioassay with pale western cutworm larvae. These results show that rhizosphere-inhabiting bacilli are indeed a potential route for introduction of &dgr; -endotoxins to the root environment for biocontrol purposes.Key words:Bacillus thuringiensis, &dgr; -endotoxin, conjugation, sporulation, expression.

ISSN:0008-4166    

DOI:10.1139/w97-147

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Four unique strains ofPseudallescheria boydiiwere isolated from oil-soaked soils in British Columbia and Alberta and compared to strains from cattle dung and raw sewage. Considerable variability in morphology, colony appearance, colony diameter, and temperature tolerance occurred among the strains. They also varied in the sporogenous states produced in culture; all strains had aScedosporiumanamorph and either theGraphiumanamorph or cleistothecial teleomorph. Conspecificity of the six isolates was inferred from their morphology and supported by restriction fragment length polymorphism profiles of the internally transcribed spacer region of rDNA and comparing these toPetriella sordida, a similar taxon in the Microascaceae. Three of the strains isolated from oil-contaminated soil and the strain from sewage were tested for their ability to utilize hydrocarbons by incubation with Prudhoe Bay Crude oil as the sole carbon source. Gas chromatographic analysis of the residual oil revealed that the strains isolated from oil-contaminated soil degraded the linear aliphatics. The strain from sewage, previously shown by others to utilize the volatilen-alkanes (i.e., ethane, propane, and butane), did not utilize the liquid saturate compounds. None of the strains was observed to degrade compounds in the aromatic fraction.Pseudallescheriaboydiimay be an important agent for in situ bioremediation of saturates in oil-contaminated sites.Key words: bioremediation, filamentous fungi,Graphium, hydrocarbon degradation,Scedosporium.

ISSN:0008-4166    

DOI:10.1139/w97-152

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Several strains of three new taxa of haploid heterothallic yeasts have been isolated from various ephemeral flowers and associated insects in North and South America and Australia.Metschnikowia continentaliscomprises two varieties and is a close relative ofMetschnikowia hawaiiensis. Like the latter, it produces giant ascospores and lives in association with the insects that colonize flowers of the family Convolvulaceae. These species exhibit an unusual asymmetrical mating, but their rare asci are sterile. The varieties ofM. continentalisundergo unlimited mating, but ascospores are rarely formed.Metschnikowia continentalisvar.continentaliswas isolated in central Brazil and is thought to occur across South America.Metschnikowia continentalisvar.borealiswas recovered in the Great Lakes area and may represent a North American population.Metschnikowia hibisciwas found in the flowers and insects of variousHibiscusspecies in the Australian states of New South Wales and Queensland but appeared to be absent in members of the Convolvulaceae growing in the same areas. The latter forms intermediate-sized ascospores and one of its mating types forms conjugation tubes in the presence of cells of otherMetschnikowiaspecies. The three taxa share withM. hawaiiensisa large deletion in the D2 region of their large ribosomal DNA subunit, but inM. hibisci, the variable domain of the D2 region shares little, if any, sequence similarity with others. The type cultures are as follows:M. continentalisvar.continentalisstrains UFMG96-173 (h+, CBS8429) and UFMG96-179 (h-, CBS8430);M. continentalisvar.borealisstrains UWO(PS)96-104.2 (h+, CBS 8431) and UWO(PS)96-101.1 (h-, CBS8432); andM. hibiscistrains UWO(PS)95-797.2 (h+, CBS8433) and UWO(PS)95-805.1 (h-, CBS8434).Key words:Metschnikowia, yeast, Convolvulaceae,Hibiscus, geographic speciation.

ISSN:0008-4166    

DOI:10.1139/w97-148

出版商:NRC Research Press    

年代:1998

数据来源: NRC