摘要:

Sorghum (Sorghum bicolor(L.) Moench cv. Bok 8) plants were grown in either a high peat or a low organic matter substrate and inoculated with a pigmented strain ofAzospirillum brasilense(Cd). Half of the plants were also inoculated with the vesicular–arbuscular mycorrhizal (VAM) fungusGlomus etunicatum, while the remaining plants were fertilized with levels of phosphorus that had been found to be comparable to P input resulting from mycorrhizal colonization. Plants were harvested 1, 3, 5, and 7 weeks postemergence. Total plant dry weight was statistically similar (p > 0.05) between the two treatments for each substrate at all harvests. For each substrate,Azospirillumcounts per gram of root were significantly (p < 0.05) higher in mycorrhizal roots at all harvests than in P-fertilized roots, and also higher in the high peat substrate compared with the low organic matter substrate. The ratio of the total number of inoculatedA.brasilensecells in theGlomus-colonized compared to the P-fertilized roots was positively and significantly correlated (r = 0.81;p < 0.05) with %VAMcolonization. Colonization of sorghum roots byG.etunicatumthus enhanced the establishment and persistence ofA.brasilensein the endorhizosphere of sorghum.Key words:Azospirillum brasilense, endomycorrhizae,Glomus etunicatum, rhizosphere,Sorghum bicolor.

ISSN:0008-4166    

DOI:10.1139/m89-163

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

This paper describes a procedure which allows the quantitative selection of auxotrophs of the fungusAspergillus nigerby enzymatic killing of immobilized germinating prototrophic conidiospores. We have applied this procedure to linkage analysis on the basis of mitotic crossing-over in this fungus. Starting with a heterozygous diploid strain, we could select auxotrophic homozygous diploid recombinants quantitatively. We estimated the frequency of crossing-over after correction for clonal distribution of recombinants, and localized four auxotrophic markers as well as the centromere on chromosome V of this fungus. The Novozym enrichment procedure proved to be useful in genetic analysis and for the construction of recombinant genotypes in the case of closely linked auxotrophic markers. The detemination of gene order and the estimation of distances on the basis of benomyl-induced recombinant haploid segregants may lead to incorrect conclusions. Genetic analysis on the basis of homozygous recombinants, however, can provide reliable estimates of map distances.Key words:Aspergillus niger, chromosome mapping, mitotic crossing-over, Novozym enrichment, auxotrophic recombinants.

ISSN:0008-4166    

DOI:10.1139/m89-164

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

To determine the relative importance of maternal microflora (faeces, vagina, and teats) in the contamination of newborn rats, strains of staphylococci from six different families (dam + litter) were isolated. These strains were identified, and by means of numerical profiles analyzed for their degree of similarity for each litter and (or) biotope. The staphylococci strains found in the gut of the newborn rat originated first from the teats and thereafter from the faeces. Concomitant observation of some identical strains, however, suggested a certain degree of similarity between these two maternal biotopes in this animal.Key words: intestinal microflora, newborn, dam, staphylococci, numerical taxonomy.

ISSN:0008-4166    

DOI:10.1139/m89-165

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Coliphage K30 lysates contain free and phage-associated forms of a bacteriophage-encoded capsule depolymerase (glycanase) enzyme, active against the serotype K30 capsular polysaccharide ofEscherichia coli. The free glycanase has been purified to apparent homogeneity. The molecular weight of the enzyme was estimated at 450 000, and when heated in SDS at 100 °C, the enzyme dissociated into two subunits of 90 000 and 52 000. The glycanase enzyme was used as a reagent to reversibly degrade the capsular layers on cells ofEscherichia coliO9:K30 andKlebsiellaO1:K20. This treatment rendered these bacteria sensitive to their respective lipopolysaccharide-specific bacteriophages, coliphage O9-1 andKlebsiellaphage O1-3. This novel approach facilitated isolation of lipopolysaccharideOantigen side chain deficient mutants which retained the ability to synthesize the capsule. The response of defined mutants,O+:K−,O−:K+, andO−:K−, to exposure to nonimmune rabbit serum was measured. Results showed that the primary barrier against complement-mediated serum killing in bothEsherichia coliO9:K30 andKlebsiellaO1:K20 was theOantigen side chains of the lipopolysaccharide molecules. In both strains, the capsule played no role in the determination of serum resistance.Key words: bacteriophage, glycanase, lipopolysaccharide, serum resistance, capsular polysaccharide.

ISSN:0008-4166    

DOI:10.1139/m89-166

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The cytotoxic effect of the cyclodepsipeptide mycotoxins of the group of destruxins (DA, DB, DE) has been investigated in the insect host,Galleria mellonella, and in invertebrate cell cultures, mainly at the ultrastructural level. The strong effect of DE is characterized by changes in the morphology of the cells, and the development of structural alterations at the nuclear and cytoplasmic levels. The major lesions observed even at low doses consist in a pycnotic evolution of the nucleus and a degradation of mitochondria, while the rough endoplasmic reticulum and the ribosomes are also impaired. In the host, the main organs and tissues attacked by DE are the midgut, the malpighian tubules, and the circulating hemocytes. A comparative study of the effect of DE, DA, and DB has revealed a specificity in the cytotoxic action of these compounds. The following classification has been observed in the efficiency of the molecules: DE > DA > DB. These results allow a better understanding of the role of peptidic mycotoxins in the pathogenesis of fungal infections. They also reveal similarities with the action of other mycotoxins, and constitute a valuable foundation for studies on the molecular aspects of the mechanism of action of destruxins.Key words: mycotoxin, destruxin, mode of action, cytotoxic effect,in vitrotoxicity.

ISSN:0008-4166    

DOI:10.1139/m89-167

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Sonically disrupted cells from avirulent strain Shibaura ofLeptospira interrogansserovarcopenhageniinduced a skin reaction characterized by infiltration of polymorphonuclear leukocytes (PMN) associated with some edema in guinea pigs. To determine the substance inducing infiltration of PMN, lipids of avirulent strain Shibaura were extracted with chloroform – methanol – water after washing with acetone. The lipids comprised 28% of the dry weight of the cell. When the lipids were further separated into water–methanol and chloroform fractions, the most severe PMN infiltration of all samples was seen in the skin inoculated with extract recovered from the chloroform fraction. Neutral and polar lipids were detected after thin-layer chromatography of the chloroform extract. Neutral lipids were detected as free fatty acids (FFA). Fatty acids contained in polar lipids were mainly palmitic acid and palmitoleic acid, whereas FFA comprised 66.5% oleic acid. Skin reactions consisting of marked edema with mild infiltration of PMN were elicited by FFA. There was no obvious difference between a commercially available FFA mixture and the FFA from avirulent strain Shibaura. These observations suggest that FFA may play some role in the pathogenesis of leptospirosis.Key words:Leptospira interrogansserovarcopenhageniavirulent strain Shibaura, polar lipids, free fatty acids, skin reaction.

ISSN:0008-4166    

DOI:10.1139/m89-168

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

We report in this study the isolation of marine bacteria with antiviral properties that have been tentatively classified asMoraxella. These bacteria retained their virucidal capacity after prolonged subcultivation in the laboratory. The virus-inactivating agent could not be separated from the viable marine bacteria, indicating that the active agent(s) either remains associated to the microorganisms or has a very short lifetime, or both. The antiviral capacity of the isolated microorganisms was highly specific for poliovirus. No virucidal effect was observed against other strains of enteroviruses, such as Coxsackie andECHOvirus, rotavirus SA11, or bacteriophages proposed as indicators of the virological quality of water, such as coliphage f2 and bacteriophage B40-8, which infectsBacteroides fragilis.Key words: enterovirus, rotavirus, coliphages, bacteriophages, seawater, marine bacteria, antiviral activity, virus survival.

ISSN:0008-4166    

DOI:10.1139/m89-169

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Far-ultraviolet radiation (254 nm) at a dose of 10, 20, and 30 J/m2was found to disrupt the outer membrane permeability barrier ofEscherichia colito various antibiotics, dyes, and detergents. The degree of sensitization to these agents was proportional to the radiation dose. The irradiated cells showed a significant increase in the sensitivity of hydrophilic antibiotics (ampicillin, carbenicillin, penicillin), whereas much less sensitization was found towards hydrophobic probes (kanamycin, erythromycin, rifamycin SV, crystal violet, phenol, novobiocin) and detergents (dodecyl sulfate, bile salt, Triton X-100). The biochemical data and ultrastructural analysis of the outer membrane by freeze-etching have shown that the increase in phospholipid:protein ratio after irradiation had changed the architecture of the outer membrane from a highly asymmetric bilayer structure with densely packed lipopolysaccharide–protein particles on the outer half, to one predominantly exhibiting smooth phospholipid bilayer characteristics. The structure, composition, and barrier function of the outer membrane were restored to normal within 3 h of postirradiation incubation in nonproliferative medium. During this period, the acquisition of resistance towards a hydrophilic antibiotic (ampicillin) was faster than that for a hydrophobic agent (phenol).Key words: far-ultraviolet, outer membrane, permeability, disorganization, recovery.

ISSN:0008-4166    

DOI:10.1139/m89-170

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The microbial dissimilation of long-chain dialkyl ethers byAcinetobactersp. H01-N involved a terminal methyl group oxidation of the dialkyl ether substrates, resulting in the formation of ether oxygen containing fatty acids of corresponding chain length. An internal carbon–carbon scission of the dialkyl ethers resulted in the formation of end-product ether fatty acids and corresponding dicarboxylic acids. Cellular carbon and energy were derived from the subsequent metabolism of the dicarboxylic acids. Dicarboxylic acid oxidation, activation, and identification of cellular dicarboxylic acids indicated dibasic acids as intermediates in the metabolism of dialkyl ethers.Key words: dialkyl ethers, dicarboxylic acids, fatty acids,Acinetobacter.

ISSN:0008-4166    

DOI:10.1139/m89-171

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Serratia marcescensproduced a brown pigment when grown in minimal medium in the presence of tyrosine and high concentrations of copper(II) ion. The pigment was not related to the melanin pigments, but was similar to the pigment produced by autooxidation and polymerization of 3,4-dihydroxyphenylacetate, which is synthesized inS.marcescensfrom tyrosine through the 3,4-dihydroxyphenylacetate catabolic pathway. The enzymes of this pathway were induced under pigment production conditions; however, 3,4-dihydroxyphenylacetate 2,3-dioxygenase remained at low activity levels, permitting the accumulation and excretion of the substrate. Mutants unable to use tyrosine as a sole carbon and energy source were able to produce brown pigments only if the step blocked by the mutation was after the synthesis of 3,4-dihydroxyphenylacetate. The ability to produce brown pigments was common to all theS.marcescensstrains tested.Key words: brown pigment, 3,4-dihydroxyphenylacetate 2,3-dioxygenase,Serratia marcescens, tyrosine, aromatic amino acid catabolism.

ISSN:0008-4166    

DOI:10.1139/m89-172

出版商:NRC Research Press    

年代:1989

数据来源: NRC