Showing papers in "Canadian Journal of Microbiology in 1990"

Current status of Azospirillum inoculation technology: Azospirillum as a challenge for agriculture

Abstract: The genus Azospirillum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Effect of Azospirillum inoculation on plants . . . . . . . . . . . . . . . .. . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . Inoculation effects on root development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Root colonization by Azospirillum . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Proposed mode of action of Azospirillum on plant growth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nitrogen fixation by Azospirillum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hormonal effects of Azospirillum on plants . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Improvement of root development, mineral uptake, and plant-water relationships by Azospirillum.. . . . . . . . . . . . Azospirillum nitrate reductase in plants . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Specificity and variability in Azospirillum. . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . Interaction of Azospirillum with other soil-rhizosphere microflora . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . Azospirillum as a competitor in the rhizosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interaction of Azospirillum with soil particles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Genetics and immunology of Azospirillum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Agrotechnical aspects: inoculants and interaction with pesticides. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Concluding remarks and future prospects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Plant growth promoting rhizobacteria for winter wheat

Abstract: The association of winter wheat (Triticum aestivum L. 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 as Pseudomonas aeruginosa, and two each as Pseudomonas cepacia, Pseudomonas fluorescens, and Pseudomonas putida. Some isolates induced significant increases in seedling emergence rates and (or) demonstrated antagonism in vitro against Rhizoctonia solani and Le...

Antibiotic resistance indexing of Escherichia coli to identify sources of fecal contamination in water

Abstract: A total of 202 Escherichia coli isolated from urban and rural water were tested with 11 antibiotics to assess the prevalence of antibiotic resistance from each source. Urban waters harbored higher ...

Mineralization of [14C]hexadecane and [14C]phenanthrene in crude oil: specificity among bacterial isolates.

Abstract: Bacteria isolated from freshwater, marine, and estuarine samples were tested for the ability to produce 14CO2 from n-[1-14C]hexadecane or [9-14C]phenanthrene added to Prudhoe Bay crude oil. Of 138 isolates tested, 54 (39%) mineralized the model aliphatic compound hexadecane and 6 (4%) mineralized the model aromatic compound phenanthrene. None mineralized both compounds. There was no apparent correlation between degradative ability and genus or source. Additional hydrocarbon-degrading bacteria from diverse sources were tested and found to mineralize either hexadecane or phenanthrene. Of 61 hexadecane- and 21 phenanthrene-mineralizing bacteria tested, none mineralized both model compounds. Selected isolates and commercially available cultures were tested for mineralization of specific 14C-labelled mono-, di-, and tri-cyclic aromatics. An apparent hierarchy of degradation was observed: strains mineralizing the mono- and di-cyclic aromatics toluene and naphthalene did not mineralize biphenyl or the tricyclic aromatics anthracene and phenanthrene, whereas those strains that mineralized the tricyclic aromatics also mineralized the smaller substrates. Similarly, not all n-alkane-mineralizing isolates tested mineralized the isoprenoid pristane. A combined culture consisting of one aliphatic- and one aromatic-degrading isolate was tested for mineralization of the model compounds and for degradation of other crude oil components by gas chromatography. No synergism or antagonism was observed compared with degradation by the individual isolates.

Accumulation of radiocaesium in fungi

Abstract: The accumulation of radioactive Cs by fungi was studied by analysis of fruit bodies (n (total) = 205, n ≥ 5 for 22 species) collected in 1988 in a Norwegian mountain area with high deposition of radiocaesium from the Chernobyl accident. To account for site variation, the radiocaesium content of soil and plants was determined for each sampling spot. The soil contained 5–600 kBq/m2 (median = 50 kbq/m2, 134Cs + 137Cs). The plant content ranged from 0.25 to 23 Bq/g dry weight (median = 3.1 Bq/g) and was positively correlated with radiocaesium concentration in the soil (r = 0.56) and negatively correlated with soil pH (r = −0.28). The ratio between radiocaesium content in fungi and that in plants at the same spot (F/P) differed among species: 25 species had F/P values between 30 and 270, 12 species had F/P values between 10 and 30, and the rest (16 species) had F/P values below 10 (only four samples had values below 1). The concentration of nonradioactive Cs in fruit bodies was positively correlated with their...

A biometric study of higher alcohol production in Saccharomyces cerevisiae.

Abstract: A hundred strains of Saccharomyces cerevisiae were examined for the ability to produce higher alcohols. In the strains tested the production of higher alcohols was found to be an individual strain ...

Receptors for transferrin in pathogenic bacteria are specific for the host's protein.

Abstract: Transferrin receptors detected by a solid-phase binding assay were shown to be specific for the host's transferrin in the representative bacterial pathogens Neisseria meningitidis (human), Pasteurella haemolytica (bovine), and Actinobacillus pleuropneumoniae (porcine). Consistent with the receptor specificity, iron-deficient bacteria were only capable of utilizing transferrin from the host as a source of iron for growth. Key words: iron, transferrin, receptor.

Pathogenicity of Staphylococcus lugdunensis, Staphylococcus schleiferi, and three other coagulase-negative staphylococci in a mouse model and possible virulence factors.

Abstract: Staphylococcus lugdunensis and Staphylococcus schleiferi, two newly described species, have been isolated from numerous types of human infections. We compared the pathogenicity of 30 strains of S. ...

Survival and inoculum potential of conidia and chlamydospores of Fusarium oxysporum f.sp. lini in soil.

Abstract: The kinetics of survival and inoculum potential of Fusarium oxysporum f. sp. lini were studied in soil. Two types of inoculum were compared: microconidia freshly harvested from a laboratory-grown c...

Purification and properties of extracellular proteases produced by the nematophagous fungus Verticillium suchlasporium.

Abstract: The fungal parasite of eggs of cyst nematodes, Verticillium suchlasporium, produced extracellular proteases when grown in semiliquid culture with gelatin as the only source of nitrogen and carbon. The proteolytic activity of culture filtrates was maximum 12–14 days after inoculation. Gel filtration chromatography in Sephadex G-100 resolved two peaks of proteolytic activity. The peak accounting for most of the activity was further purified by ion-exchange chromatography in SP-Sephadex C-25 as a single peak. This protease had a molecular mass of 32 kDa calculated by sodium dodecyl sulfate – polyacrylamide gel electrophoresis. The enzyme was an endopeptidase that degraded fibrinogen in zymograms and had an optimum pH of 8.5 using fluorescein isothiocyanate – casein as the substrate. It was inhibited by phenylmethylsulfonyl fluoride, indicating that it was a serine protease. The purified protease was able to degrade certain cyst nematode proteins suggesting the involvement and specificity of the 32-kDa protea...

Physiology of biosurfactant synthesis by Rhodococcus species H13-A.

Abstract: The physiology of biosurfactant synthesis by a soil isolate, identified as a Rhodococcus species, is described. The biosurfactant is a surface-active glycolipid produced during the stationary growth phase of Rhodococcus species H13-A on n-alkanes and fatty alcohols in response to limiting ammonium ion concentrations. Hexadecane-grown cells produced increasing amounts of extracellular glycolipid when the carbon to nitrogen ratio (C/N) was increased from 1.7 to 3.4. The increase in extracellular glycolipid in hexadecane-grown cells correlated with a decrease in the interfacial tension of the spent growth medium to values less than 5 mN/m. Significant levels of extracellular glycolipid were not detected in the spent growth medium of cells grown on triglycerides, fatty acids, ethanol, organic acids, or carbohydrates. Rhodococcus species H13-A contains the three indigenous plasmids pMVS100, pMVS200, and pMVS300, with neither pMVS200 nor pMVS300 being involved in glycolipid synthesis or hexadecane dissimilation. The role of pMVS100 remains undetermined. Key words: biosurfactants, glycolipids, trehalose lipids, Rhodococcus.

Glucose oxidase as the antifungal principle of talaron from Talaromyces flavus.

Abstract: Analysis of an authentic sample of the antifungal antibiotic talaron from the biocontrol fungus Talaromyces flavus indicated that approximately 40% of the solid sample was glucose oxidase. High-per...

Host plant effect on competition among strains of Rhizobium leguminosarum

Abstract: Analysis of plasmid profiles was used to type Rhizobium leguminosarum biovar viciae strains isolated from nodules of peas, lentils and faba beans grown in two different soils One soil was from a native pasture with no previous history of cultivation, the other was from a plot in a rotation study which included lentils every 2 years The results indicated a strong preference of both peas and faba beans for strains having certain specific plasmid profiles Strains belonging to one plasmid profile group (group 2) formed over half the nodules on peas grown in soil from the rotation plot but were never found on faba beans grown in the same soil, while strains from another group (group 5) formed nearly all of the nodules on faba beans grown in soil from the rotation plot, but no nodules on peas Competitiveness for pea nodulation was correlated with an ability to catabolize homoserine, an amino acid found in large quantities in pea root exudate Strains having plasmid profiles corresponding to those of strains

Disinfection of bacteria in water systems by using electrolytically generated copper:silver and reduced levels of free chlorine.

Abstract: As an alternative disinfectant to chlorination, electrolytically generated copper:silver (400 and 40 μg/L copper and silver, respectively) with and without free chlorine (0.3 mg/L) was evaluated ov...

Trichoderma protoplast fusion: a tool for improving biocontrol agents

Abstract: Protoplasts from two auxotrophic mutants of Trichoderma harzianum Rifai (ATCC 32173), obtained from young thalli following cell wall digestion by NovoZym 234, were fused in 33% PEG suspended in 10 ...

Fluctuations in the fluorescent pseudomonad and actinomycete populations of rhizosphere and rhizoplane during the growth of spring wheat

Abstract: 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...

Possible mode of action of Azospirillum brasilense strain Cd on the root morphology and nodule formation in burr medic (Medicago polymorpha)

Abstract: The mechanism(s) involved in the effect of Azospirillum brasilense strain Cd on root susceptibility to nodulation was studied in medic seedlings grown in pouches. The number of nodules above the position of the root-tip mark at the time of inoculation and the position of the uppermost nodule were used as parameters for determining the rate of nodule initiation. Cell-free extracts and culture supernatants prepared from Azospirillum and the cytokinin benzyladenine (10−9 M) significantly increased the number of nodules formed above the root-tip mark when applied together with Rhizobium compared with those formed with Rhizobium alone. The application of indoleacetic acid did not cause an increase in the number of nodules. In the absence of Rhizobium, exposure to Azospirillum at a concentration of 109 cfu/mL or to compounds excreted by the bacteria into the growth medium caused a 40% increase in endogenous ethylene production by the roots. A less concentrated inoculum did not increase ethylene production. Inoc...

Inability of human clinical strains of Helicobacter pylori to colonize the alimentary tract of germfree rodents.

Abstract: Several attempts were made to colonize the alimentary tract and infect germfree BALB/c mice and germfree Sprague-Dawley rats with two human isolates of Helicobacter pylori. The alimentary tracts of mice, sacrificed at intervals between 1 day and 20 weeks after oral challenge, were culture negative for H. pylori. The alimentary tract, kidney, liver, and mesenteric lymph nodes were culture negative for H. pylori 5 h after intravenous challenge. Growth of H. pylori was 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 of H. pylori.

Short exposure to Azospirillum brasilense Cd inoculation enhanced proton efflux of intact wheat roots.

Abstract: Inoculation of wheat seedlings with Azospirillum brasilense Cd significantly increased the proton efflux of the roots 5 h after inoculation compared with noninoculated plants. Removal of the bacterial cells from the root surface 2, 4, or 10 h after inoculation did not affect proton extrusion, which remained similar to the proton efflux of inoculated roots with a permanent A. brasilense Cd population. Proton efflux from roots after short exposure to A. brasilense Cd was directly related to the inoculation level and to the physiological status of the bacterial cells. Active bacteria, at an optimal level for inoculation (105–107 cfu∙mL−1), produced the most proton extrusion from roots. Stressed bacteria, i.e., bacteria exposed to starvation, 45 °C, anaerobic conditions, or a high level of streptomycin before inoculation, induced smaller but not statistically significant increases in proton efflux. Inoculation with dead A. brasilense Cd cells, cell-wall fragments, or several associative nonbeneficial rhizosph...

The role of hydrogenase in anaerobic biocorrosion.

Abstract: 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 from Clostridium pasteurianum was 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.

Interaction of the Bacillus sphaericus mosquito larvicidal proteins.

Abstract: Genes for 51.4- and 41.9-kDa insecticidal proteins of Bacillus sphaericus were separately cloned and expressed in Escherichia coli. Both proteins were required for toxicity. Approximately equal numbers of cells containing the 51.4- and 41.9-kDa proteins produced the greatest toxicity; excess 41.9-kDa protein did not affect toxicity, whereas excess 51.4-kDa protein reduced activity. Larvae were killed when 41.9-kDa protein was fed up to 24 h after the 51.4-kDa protein, but not when the order of feeding was reversed. Radiolabelled toxins bound in approximately equal amounts to the gastric caecum and posterior midgut of Culex quinquefasciatus larvae. Radiolabelled 51.4-kDa protein was rapidly degraded by ca. 12–13 kDa in the larval gut, while 41.9-kDa protein was degraded by 1–2 kDa. Nonreduced toxin extracted from B. sphaericus produced a band on SDS–PAGE of ca. 68–74 kDa that contained both 51.4- and 41.9-kDa proteins based on sequence analysis, and a band of ca. 51 kDa that contained primarily 41.9-kDa protein. Escherichia coli containing 51.4-kDa protein enhanced toxicity of the latter eluted SDS-PAGE band. These proteins may associate very strongly, and trace amounts of 51.4-kDa protein in preparations of 41.9-kDa protein from B. sphaericus may be responsible for the previously reported toxicity of the latter.

Inactivation of viral agents in bovine serum by gamma irradiation

Abstract: Cell culture origin or suckling mouse brain origin viruses of Akabane disease, Aino, bovine ephemeral fever, swine vesicular disease, hog cholera, bluetongue, and minute virus of mice were each sus...

Preliminary characterization of four bacteriocins from Streptococcus mutans

Abstract: The various properties of the inhibitory substances produced by Streptococcus mutans strains C67-1, Ny257-S, Ny266, and T8, and the fact that inhibitory zones produced could not be associated with ...

Degradation of phenol by a bacterial consortium under methanogenic conditions

Abstract: An anaerobic bacterial consortium was shown to carboxylate phenol to benzoate under methanogenic conditions Benzoate accumulated in the culture medium and was completely degraded when the incubation period was prolonged Two potential intermediates of phenol metabolism, namely cyclohexanol and cyclohexanone, were not accumulated or transformed by the consortium Proteose peptone must be added to the culture medium for the carboxylation of phenol to occur and glucose could not replace proteose peptone Inhibition of methanogenesis did not affect the carboxylation of phenol and the presence or absence of hydrogen in the gaseous atmosphere did not prevent the accumulation of benzoate The consortium was composed of various microbiological forms dominated by Gram-negative rods Phenol-carboxylating microorganisms were evaluated to about ≥ 1 × 108 cells/mL by using diluted inocula These results suggest that the carboxylation of phenol is accomplished by co-metabolism and that proteose peptone or some degrada

Production, purification, and properties of glucose oxidase from the biocontrol fungus Talaromyces flavus

Abstract: Talaromyces flavus produces the enzyme glucose oxidase, which may be involved in biocontrol of the fungal plant pathogen, Verticillium dahliae. A strain of T. flavus was selected from the wild-type population for the production of extracellular glucose oxidase, and the enzyme was purified by a combination of acetone precipitation and high performance liquid chromatography (HPLC). Approximately 12–25 mg of pure protein was obtained from 2 L of culture, and the total recovered activity ranged from 5 to 10 × 103 μmol/min. Homogeneity of the purified enzyme was demonstrated by HPLC and by native and sodium dodecylsulfate polyacrylamide gel electrophoresis. Molecular weight of the native enzyme was 164 000 and that of the subunit was71 000, which indicated that the native enzyme is a dimer. The apparent Km value for D-glucose was 10.9 mM. The optimum pH for the enzyme activity was 5.0, but the enzyme was stable in buffer from pH 3 to 7. The enzyme was observed to be a glycoprotein, and amino acid analysis of t...

Vegetative compatibility within Fusarium oxysporum f.sp. niveum and its relationship to virulence, aggressiveness, and race

Abstract: Over 250 isolates of Fusarium oxysporum collected from infected watermelon plants and soil samples from a pathogen-infested field, as well as known isolates of F. oxysporum f. sp. niveum imported from various locations around the world, were tested for pathogenicity on watermelon and used to determine vegetative compatibility groups (VCGs) within F. oxysporum f. sp. niveum. Vegetative compatibility was assessed on the basis of heterokaryon formation among nitrate-nonutilizing mutants. Race determinations were made by screening isolates on six different watermelon cultivars of varying resistance. All isolates of F. oxysporum f. sp. niveum belonged to one of three distinct VCGs, and were incompatible with isolates that were not pathogenic on watermelon. Isolates of F. oxysporum f. sp. niveum were subdivided into two races and there was a direct relationship between VCG and race. VCG 0080 consisted of race 1 isolates from five states of the United States, Taiwan, and Australia. VCG 0081 consisted solely of r...

Promiscuous nodulation of Phaseolus vulgaris, Macroptilium atropurpureum, and Leucaena leucocephala by indigenous Rhizobium meliloti

Abstract: Thirty-three isolates of indigenous Rhizobium meliloti, either possessing cryptic plasmids that hybridize to probes for symbiotic genes or lacking a 1500-kb megaplasmid band in Eckhardt gels, were tested for infectivity on 10 legume species grown under axenic conditions. A previous study had shown that all but two isolates were symbiotically effective with Medicago sativa. All indigenous isolates and two reference strains of R. meliloti induced nodules which were symbiotically ineffective on Trigonella foenum-graecum (100% plants nodulated) and Phaseolus vulgaris (40 to 100% plants nodulated). Eighteen indigenous isolates of R. meliloti elicited ineffective nodules on Macroptilium atropurpureum (2 to 25% plants nodulated) and Leucaena leucocephala (11 to 75% plants nodulated). The identity of single colony nodule isolates from each R. meliloti inoculant and host combination was verified by phage typing and analysis of plasmid profiles; tests with subsamples of these isolates showed that all were capable o...

Expression of a Bacillus thuringiensis crystal protein gene in Pseudomonas cepacia 526

Abstract: An insecticidal crystal protein gene, cryIA(C), from Bacillus thuringiensis HD-1 was cloned into a broad host range vector, pSUP204, and the resulting plasmid, pSUP89A, was conjugated into a plant-colonizing bacterium, Pseudomonas cepacia 526. Southern blot analysis detected the presence of the cry gene in Pseudomonas cepacia 526 transconjugants. Production of a truncated insecticidal crystal protein in Pseudomonas cepacia was detected by Western blotting and ELISA techniques and was found to have insecticidal activity against the tobacco hornworm, Manduca sexta, in an artificial diet assay. We also followed the establishment of the Pseudomonas cepacia 526/Bt transconjugant on axenically grown tobacco plants and found that approximately 1% of the Pseudomonas cells retained pSUP89A 3 days after application. In spite of this instability, treated tobacco plants were protected from Manduca sexta infestation. Key words: Bacillus thuringiensis, Pseudomonas cepacia, insecticidal crystal protein, Cry protein.

Influence of elevation and applied nitrogen on rhizosphere colonization and competition for nodule occupancy by different rhizobial strains on field-grown soybean and common bean

Abstract: In the absence of indigenous rhizobial populations, the pattern of competition between inoculum strains for nodule occupancy is found to be a stable characteristic, independent of rhizosphere population size, nitrogen application, or elevation. Soybean (Glycine max (L.) Merrill) and common bean (Phaseolus vulgaris L.), inoculated with peat-based rhizobia, were grown with three nitrogen levels at 320- and 150-m sites along an elevational transect on the island of Maui, Hawaii. Rhizosphere soil of 8-day-old plants was examined by immunofluorescence for populations of three strains each of Bradyrhizobium japonicum and Rhizobium leguminosarum bv. phaseoli, which made up the inocula applied to the respective host legumes at planting. Nodules were examined for occupancy by specific strains at two sampling times. Site differences and nitrogen treatment had no significant effect on rhizosphere colonization or nodule occupancy by the three strains. The three inoculum strains colonized their respective host rhizosp...