| 1. |
- Björnberg, Anna, et al.
(författare)
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Inhibition of the growth of grain-storage molds in vitro by the yeast Pichia anomala (Hansen) Kurtzman
- 1993
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Ingår i: Canadian journal of microbiology (Print). - Montreal, Canada : Canadian Science Publishing. - 0008-4166 .- 1480-3275. ; 39:6, s. 623-628
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Tidskriftsartikel (refereegranskat)abstract
- The potential Use Of yeasts to control grain-storage molds was evaluated by coculturing the yeast Pichia anomala with Penicillium roqueforti and Aspergillus candidus on agar plates, using different temperatures, water activities (a(w)), and nutrient concentrations. Addition of 10 ppm cycloheximide to malt-extract agar inhibited Pichia anomala completely without affecting mold growth, making it possible to quantify the inhibition as a reduction in colony-forming units (cfu). For A. candidus, numbers of cfu and hyphal lengths were reduced at an initial yeast concentration of 10(4) cells/plate and reduced below detection limit at 10(8) cells/plate. A clear reduction in growth of Penicillium roqueforti was only observed at 10(8) yeast cells/plate. The antagonistic effect was generally more pronounced at low (6, 15-degrees-C) and high (30, 37-degrees-C) temperatures than at ambient ones. Pichia anomala inhibited growth of both molds more strongly in a substrate-rich medium than in a medium with a low substrate content. In water agar (low substrate concentration) the degree of inhibition of Penicillium roqueforti was larger at 0.96 a(w) than at 0.98 a(w).
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| 2. |
- de Boer, Wietse, et al.
(författare)
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Mechanism of antibacterial activity of the white-rot fungus Hypholoma fasciculare colonizing wood
- 2010
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Ingår i: Canadian journal of microbiology (Print). - : NRC Research Press. - 0008-4166 .- 1480-3275. ; 56:5, s. 380-388
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In a previous study it was shown that the number of wood-inhabiting bacteria was drastically reduced after colonization of beech (Fagus sylvatica) wood blocks by the white-rot fungus Hypholoma fasciculare, or sulfur tuft (Folman et al. 2008). Here we report on the mechanisms of this fungal-induced antibacterial activity. Hypholoma fasciculare was allowed to invade beech and pine (Pinus sylvestris) wood blocks that had been precolonized by microorganisms from forest soil. The changes in the number of bacteria, fungal biomass, and fungal-related wood properties were followed for 23 weeks. Colonization by the fungus resulted in a rapid and large reduction in the number of bacteria (colony-forming units), which was already apparent after 4 weeks of incubation. The reduction in the number of bacteria coincided with fungal-induced acidification in both beech and pine wood blocks. No evidence was found for the involvement of toxic secondary metabolites or reactive oxygen species in the reduction of the number of bacteria. Additional experiments showed that the dominant bacteria present in the wood blocks were not able to grow under the acidic conditions (pH 3.5) created by the fungus. Hence our research pointed at rapid acidification as the major factor causing reduction of wood-inhabiting bacteria upon colonization of wood by H. fasciculare.
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| 3. |
- Frändberg, Emma, et al.
(författare)
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Antifungal activity of chitinolytic bacteria isolated from airtight stored cereal grain
- 1998
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Ingår i: Canadian journal of microbiology (Print). - : NRC Research Press. - 0008-4166 .- 1480-3275. ; 44:2, s. 121-127
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Tidskriftsartikel (refereegranskat)abstract
- Chitinolytic bacteria are used as biocontrol agents of plant pathogenic fungi. They might also potentially inhibit growth of molds, e.g., Aspergillus spp. and Penicillium spp., in stored plant material. We isolated chitinolytic bacteria from airtight stored cereal grain and evaluated their antifungal capacity. Between 0.01 and 0.5% of the total aerobic counts were chitinolytic bacteria. Gram-negative bacteria, mainly Pseudomonadaceae, constituted approximately 80% of the chitinolytic population. Gram-positive isolates belonged predominantly to the Corynebacterium-Arthrobacter group, Streptomyces, and Bacillus. Chitinolytic activity was evaluated using culture filtrates from chitin-grown isolates as the release of p-nitrophenol from p-nitrophenyl N,N'-diacetylchitobiose and as the formation of clearing zones on chitin agar. No correlation between chitinolytic activity and antifungal effects was found when challenging Penicillium roqueforti Dierckx with bacterial isolates on chitin agar in a dual culture bioassay. Fungal hyphae frequently grew seemingly unaffected through the bacterial colony of a high chitinase producer on colloidal chitin. Only 4% of the chitinolytic isolates had strong effects on fungal growth. Among these, Streptomyces halstedii (K122) and Streptomyces coelicolor (K139) inhibited growth of a broad range of fungi. Streptomyces halstedii affected hyphal morphology and decreased the radial growth rate of all fungi investigated. These effects were not caused by volatile metabolites, polyenes, or N-carbamoyl-D-glucosamine.
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| 4. |
- Frändberg, Emma, et al.
(författare)
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Streptomyces halstedii K122 produces the antifungal compounds bafilomycin B1 and C1
- 2000
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Ingår i: Canadian journal of microbiology (Print). - : NRC Research Press. - 0008-4166 .- 1480-3275. ; 46:8, s. 753-758
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Tidskriftsartikel (refereegranskat)abstract
- Streptomyces halstedii K122 was previously found to produce antifungal compounds on solid substrates that inhibit radial growth of fungi among Ascomycetes, Basidiomycetes, Deuteromycetes, Oomycetes, and Zygomycetes, and strongly affected hyphal branching and morphology. During growth of S. halstedii K122 in submerged culture, no antifungal activity could be detected. However, cultivation of S. halstedii in thin (1 mm) liquid substrate layers in large surface-area tissue culture flasks caused intense growth and sporulation of S. halstedii K122, and the biologically active compounds could be extracted from the mycelium with methanol. Antifungal compounds were purified using C18 solid phase extraction and silica gel column chromatography, and identified as bafilomycins B1 and C1, using 2D NMR and FAB MS. Production of bafilomycins, which are specific inhibitors of vacuolar ATPases, has not been reported from S. halstedii previously. Minimum inhibitory concentrations (MIC) of bafilomycins BI and C1, amphotericin B, and nikkomycin Z were determined at pH 5.5 and 7.0 for the target fungi Aspergillus fumigatus, Mucor hiemalis, Penicillium roqueforti, and Paecilomyces variotii. Penicillium roqueforti was the most sensitive species to all the compounds investigated. The MIC values for amphotericin B were 0.5-4 mu g.mL(-1) for the fungi tested, and pH did not affect the toxicity. The MIC values for nikkomycin Z ranged from <0.5 mu g.mL(-1) for Mucor hiemalis to >500 mu g.mL(-1) for Aspergillus fumigatus, and pH had no influence on toxicity. Bafilomycins B1 and C1 were equally active against the fungal species tested, with MIC values in the range of <0.5-64 mu g.mL(-1). All fungi were more sensitive to both bafilomycin B1 and C1 at pH 7.0 than at pH 5.5.
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| 5. |
- Greiner, R, et al.
(författare)
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myo-Inositol phosphate isomers generated by the action of a phytate-degrading enzyme from Klebsiella terrigena on phytate
- 2006
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Ingår i: Canadian Journal of Microbiology. - 1480-3275 .- 0008-4166. ; 52:8, s. 759-768
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Tidskriftsartikel (refereegranskat)abstract
- For the first time a dual pathway for dephosphorylation of myo-inositol hexakisphosphate by a histidine acid phytase was established. The phytate-degrading enzyme of Klebsiella terrigena degrades myo-inositol hexakisphosphate by stepwise dephosphorylation, preferably via D-Ins(1,2,4,5,6)P-5, D-Ins(1,2,5,6)P-4, D-Ins(1,2,6)P-3, D-Ins(1,2)P-2 and alternatively via D-Ins(1,2,4,5,6)P-5, Ins(2,4,5,6)P-4, D-Ins(2,4,5)P-3, D-Ins(2,4)P-2 to finally Ins(2)P. It was estimated that more than 98% of phytate hydrolysis occurs via D-Ins(1,2,4,5,6)P-5. Therefore, the phytate-degrading enzyme from K. terrigena has to be considered a 3-phytase (EC 3.1.3.8). A second dual pathway of minor importance could be proposed that is in accordance with the results obtained by analysis of the dephosphorylation products formed by the action of the phytate-degrading enzyme of K. terrigena on myo-inositol hexakisphosphate. It proceeds preferably via D-Ins(1,2,3,5,6)P-5, D-Ins(1,2,3,6)P-4, Ins(1,2,3)P-3, D-Ins(2,3)P-2 and alternatively via D-Ins(1,2,3,5,6)P-5, D-Ins(2,3,5,6)P-4, D-Ins(2,3,5)P-3, D-Ins(2,3)P-2 to finally Ins(2)P. D-Ins(2,3,5,6)P-4, D-Ins(2,3,5)P-3, and D-Ins(2,4)P-2 were reported for the first time as intermediates of enzymatic phytate dephosphorylation. A role of the phytate-degrading enzyme from K. terrigena in phytate breakdown could not be ruled out. Because of its cytoplasmatic localization and the suggestions for substrate recognition, D-Ins(1,3,4,5,6)P-5 might be the natural substrate of this enzyme and, therefore, may play a role in microbial pathogenesis or cellular myo-inositol phosphate metabolism.Key words: myo-inositol phosphate isomers, phytate-degrading enzyme, phytate, phytase, Klebsiella terrigena.
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| 6. |
- Greiner, R, et al.
(författare)
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Pathway of phytate dephosphorylation by beta-propeller phytases of different origins
- 2007
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Ingår i: Canadian Journal of Microbiology. - 1480-3275 .- 0008-4166. ; 53:4, s. 488-495
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Tidskriftsartikel (refereegranskat)abstract
- Using a combination of high-performance ion chromatography analysis and kinetic studies, the pathway of myomositol hexakisphosphate dephosphorylation by the beta-propeller phytase of Shewanella oneidensis was established, which was then compared with that of Bacillus subtilis 168, Bacillus amyloliquefaciens ATCC 15841, and B. amyloliquefaciens 45 beta-propeller phytases. The data demonstrate that all of these beta-propeller phytases dephosphorylate myo-inositol hexakisphosphate in a stereospecific way by sequential removal of phosphate groups via D-Ins(1,2,4,5,6)P-5, In,(2,4,5,6)P-4 to finally Ins(2,4,6)P-3. Thus, the beta-propeller phytases prefer the hydrolysis of every second phosphate over that of adjacent ones. This finding does not support previous phytate degradation models proposed by J. Kerovuo, J. Rouvinen, and F. Hatzack (2000. Biochem. J. 352: 623-628) and R. Greiner, A. Farouk, M. Larsson Alminger, and N.G. Carlsson (2002. Can. J. Microbiol. 48: 986-994), but seems to fit with the structural model given by S. Shin, N.C. Ha, B.C. Oh, T.K. Oh, and B.H. Oh (2001. Structure, 9: 851-858).
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| 7. |
- Huang, Yanyan, et al.
(författare)
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A 4-year study of avian influenza virus prevalence and subtype diversity in ducks of Newfoundland, Canada.
- 2013
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Ingår i: Canadian journal of microbiology (Print). - : Canadian Science Publishing. - 0008-4166 .- 1480-3275. ; 59:10, s. 701-708
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Tidskriftsartikel (refereegranskat)abstract
- The island of Newfoundland, Canada, is at the eastern edge of North America and has migratory bird connections with the continental mainland as well as across the North Atlantic Ocean. Here, we report a 4-year avian influenza virus (AIV) epidemiological study in ducks in the St. John's region of Newfoundland. The overall prevalence of AIV detection in ducks during this study was 7.2%, with American Black Ducks contributing the vast majority of the collected samples and the AIV positives. The juvenile ducks showed a significantly higher AIV detection rate (10.6%) compared with adults (3.4%). Seasonally, AIV prevalence rates were higher in the autumn (8.4%), but positives were still detected in the winter (4.6%). Preliminary serology tests showed a high incidence of previous AIV infection (20/38, 52.6%). A total of 43 viruses were characterized for their HA-NA or HA subtypes, which revealed a large diversity of AIV subtypes and little recurrence of subtypes from year to year. Investigation of the movement patterns of ducks in this region showed that it is a largely non-migratory duck population, which may contribute to the observed pattern of high AIV subtype turnover. Phylogenetic analysis of 4 H1N1 and one H5N4 AIVs showed these viruses were highly similar to other low pathogenic AIV sequences from waterfowl in North America and assigned all gene segments into American-avian clades. Notably, the H1N1 viruses, which were identified in consecutive years, possessed homologous genomes. Such detection of homologous AIV genomes across years is rare, but indicates the role of the environmental reservoir in viral perpetuation.
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| 8. |
- Izumi, Hironari, et al.
(författare)
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Diversity of predominant endophytic bacteria in European deciduous and coniferous trees.
- 2008
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Ingår i: Canadian journal of microbiology. - : Canadian Science Publishing. - 0008-4166 .- 1480-3275. ; 54:3, s. 173-179
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Tidskriftsartikel (refereegranskat)abstract
- The diversity of endophytic bacteria residing in root, stem, and leaf tissues was examined in coniferous and deciduous tree species, Scots pine (Pinus sylvestris L.), silver birch (Betula pendula Roth), and rowan (Sorbus aucuparia L.). Using cultivation-dependent and -independent analyses, the bacterial communities were observed to be significantly different in the belowground (roots and rhizosphere) and aboveground (leaves and stems) samples of the respective host trees. No significant differences, with respect to the different tree species, were observed in the associated communities. Predominant cultivable endophytes isolated included bacteria closely related to Bacillus subtilis, Bacillus licheniformis, Paenibacillus spp., and Acinetobacter calcoaceticus. Comparisons of the most abundant cultivable bacteria in the rhizosphere and root samples suggested that root endophytic bacteria may be in residence through processes of selection or active colonization rather than by passive diffusion from the rhizosphere.
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| 9. |
- Kuhn, I, et al.
(författare)
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A 4-year study of the diversity and persistence of coliforms and Aeromonas in the water of a Swedish drinking water well
- 1997
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Ingår i: Canadian journal of microbiology. - : Canadian Science Publishing. - 0008-4166 .- 1480-3275. ; 43:1, s. 9-16
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Tidskriftsartikel (refereegranskat)abstract
- Coliforms and Aeromonas, isolated over a sampling period of 4 years from a Swedish drinking water well, were analysed for their phenotypical diversity and for their ability to persist in the well water. From each of the 40 water samples collected from the well, 32 bacterial isolates were subjected to typing by the PhenePlate (PhP) biochemical fingerprinting system. Strains able to persist in the well water were further characterized using the API 20E system, gas–liquid chromatographic cellular fatty acid analysis, and the DNA fingerprinting technique AFLP. Using the PhP system, a total of 170 different phenotypes were identified among 1143 studied isolates. Most phenotypes were only represented by a few isolates and (or) were restricted to one or two sampling occasions. However, one particular phenotype (RV-C01), identified as Aeromonas hydrophila using the API 20E system and fatty acid analysis, reoccurred in 28 samples distributed over the whole study period and often dominated the bacterial population in the well water. AFLP analysis revealed that the RV-C01 isolates displayed basically identical fingerprints. Our results thus suggest that a genetically stable Aeromonas clone resided in the well water over the whole 4-year study, whereas other bacterial strains studied were only transient inhabitants of the well.Key words: Aeromonas, coliform, water, diversity.
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| 10. |
- Mattsson, U, et al.
(författare)
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Hydrogenase in Frankia KB5 : Expression of and relation to nitrogenase
- 2000
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Ingår i: Canadian journal of microbiology (Print). - 0008-4166 .- 1480-3275. ; 46:12, s. 1091-1095
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Tidskriftsartikel (refereegranskat)abstract
- The localization and expression of the hydrogenase in free-living Frankia KB5 was investigated immunologically and by monitoring activity, focusing on its relationships with nitrogenase and H-2. Immunological studies revealed that the large subunit of the hydrogenase in Frankia KB5 was modified post-translationally, and transferred into the membrane after processing. The large subunit was constitutively expressed and no correlation was found between hydrogenase activity and synthesis. Although H-2 was not needed for induction of hydrogenase synthesis, exogenously added H-2 triggered hydrogen uptake in medium containing nitrogen, i.e., in the hyphae. A correlation between nitrogenase activity and hydrogen uptake was found in cultures grown in media without nitrogen, but interestingly the two enzymes showed no co-regulation.
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