| 1. |
- Ascencio, F, et al.
(författare)
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Production and secretion of collagen-binding proteins from Aeromonas veronii
- 2000
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Ingår i: Journal of Applied Microbiology. - : Oxford University Press (OUP). - 1364-5072 .- 1365-2672. ; 89:4, s. 607-616
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Tidskriftsartikel (refereegranskat)abstract
- Collagen-binding protein (CNBP) synthesized by Aeromonas veronii is located conserved within the subcellular fraction. The results of this study show that 98% of the total CNBP produced by Aer. veronii is present in the extracellular medium, and that the remaining CNBP is distributed either on the cell surface, within the periplasm or anchored on the outer membrane. CNBP is specifically secreted from Aer. veronii into the culture medium, because all the -lactamase activity was located in the cells and could be released by polymixin B extraction of periplasmic proteins. CNBP was produced at growth temperatures from 12 °C to 42 °C, but not at 4 °C. The findings indicate that the level of CNBP in the medium increases during the exponential growth phase and reaches a maximum during the early stationary phase. There was less CNBP production in poor nutrient MMB medium than in the rich LB nutrient medium. CNBP secretion, in contrast to aerolysin secretion, was unaffected by the exeA mutation of Aer. hydrophila. It is concluded that CNBP secretion from Aer. veronii must be achieved by a mechanism different from that reported for aerolysin secretion.
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| 2. |
- Bengtsson, Göran, et al.
(författare)
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Effects of carbon substrate enrichment and DOC concentration on biodegradation of PAHs in soil
- 2003
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Ingår i: Journal of Applied Microbiology. - : Oxford University Press (OUP). - 1364-5072 .- 1365-2672. ; 94:4, s. 608-617
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Tidskriftsartikel (refereegranskat)abstract
- Aims: Two common reasons to explain slow environmental biodegradation of polycyclic aromatic hydrocarbons (PAHs), namely lack of appropriate carbon sources for microbial growth and limited bioavailability of PAHs, were tested in a laboratory bioassay using a creosote-contaminated soil. Methods and Results: The soil, containing a total of 8 mg g(-1) of 16 PAHs, was sieved and incubated in bottles for 45 days. The first explanation was tested by enrichment with the analogue anthracene and the non-analogue myristic acid, and both failed to stimulate degradation of all PAHs except anthracene. The second explanation was tested by addition of different concentrations of dissolved organic carbon (DOC), with effects depending on the DOC concentration and the molecular size of the PAH. The degradation was enhanced from 10 to 35% for 12 PAHs when the soil was saturated. The degraded amounts of individual PAHs were proportional to their concentration in the soil. Conclusions: The slow in situ degradation of PAHs was enhanced by more than three times by adding water as a solvent. Addition of DOC facilitated the degradation of four- to six-ring PAHs. Significance and Impact of Study: Bioremediation of PAH-contaminated sites may be facilitated by creating water-saturated conditions but retarded by addition of other carbon substrates, such as analogue compounds.
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| 3. |
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| 4. |
- D'Aimmo, Maria Rosaria, 1975, et al.
(författare)
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The potential of bifidobacteria as a source of natural folate
- 2012
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Ingår i: Journal of Applied Microbiology. - : Oxford University Press (OUP). - 1365-2672 .- 1364-5072. ; 112:5, s. 975-984
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Tidskriftsartikel (refereegranskat)abstract
- Aims: To screen 19 strains of bifidobacteria for main folate forms composition in synthetic folate-free and complex folate-containing media. Methods and Results: HPLC was used to analyse deconjugated folates extracted from bacterial biomass. Most strains had a total folate content above 4000 mu g per 100 g dry matter (DM). The highest value of 9295 mu g per 100 g DM was found in Bifidobacterium catenulatum ATCC 27539 and the lowest in Bifidobacterium animalis ssp. animalis ATCC 25527 containing 220 mu g per 100 g DM. Ten strains grew in a synthetic folate-free medium (FFM), showing folate autotrophy and suggesting folate auxotrophy of the remaining nine. In the autotrophic strains, a consistently higher folate level was found in FFM as compared to a more complex folate-containing medium, suggesting reduced requirements for folates in the presence of growth factors otherwise requiring folates for synthesis. The contents of total folate, 5-CH3-H(4)folate and H(4)folate were strain dependent. 5-CH3-H(4)folate dominated in most strains. Conclusions: Our results show that bifidobacteria folate content and composition is dynamic, is strain specific and depends on the medium. Suitable selection of the growth conditions can result in high levels of folate per cell unit biomass. Significance and Impact of the Study: This suggests that certain bifidobacteria may contribute to the folate intake, either directly in foods, such as fermented dairy products, or in the intestine as folate-trophic probiotics or part of the natural microbiota.
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| 5. |
- Jarvis, Åsa, et al.
(författare)
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Activity and composition of ammonia oxidizing bacterial communities and emission dynamics of NH3 and N2O in a compost reactor treating organic household waste
- 2009
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Ingår i: JOURNAL OF APPLIED MICROBIOLOGY. - : Oxford University Press (OUP). - 1364-5072 .- 1365-2672. ; 106:5, s. 1502-1511
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Tidskriftsartikel (refereegranskat)abstract
- To monitor emissions of NH3 and N2O during composting and link these to ammonia oxidation rates and the community structure of ammonia oxidizing bacteria (AOB). A laboratory-scale compost reactor treating organic household waste was run for 2 months. NH3 emissions peaked when pH started to increase. Small amounts of N2O and CH4 were also produced. In total, 16% and less than 1% of the initial N was lost as NH3-N and N2O-N respectively. The potential ammonia oxidation rate, determined by a chlorate inhibition assay, increased fourfold during the first 9 days and then remained high. Initially, both Nitrosospira and Nitrosomonas populations were detected using DGGE analysis of AOB specific 16S rRNA fragments. Only Nitrosomonas europaea was detected under thermophilic conditions, but Nitrosospira populations re-established during the cooling phase. Thermophilic conditions favoured high potential ammonia oxidation rates, suggesting that ammonia oxidation contributed to reduced NH3 emissions. Small but significant amounts of N2O were emitted during the thermophilic phase. The significance of different AOBs detected in the compost for ammonia oxidation is not clear. This study shows that ammonia oxidation occurs at high temperature composting and therefore most likely reduces NH3 emissions.
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| 6. |
- Li, Yujing, et al.
(författare)
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Impact of temperature on growth and metabolic efficiency of Penicillium roqueforti - Correlations between produced heat, ergosterol content and biomass
- 2009
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Ingår i: Journal of Applied Microbiology. - : Oxford University Press (OUP). - 1364-5072 .- 1365-2672. ; 106:Online 4 Feb 2009, s. 1494-1501
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Tidskriftsartikel (refereegranskat)abstract
- The influence of temperature on the growth of the mould Penicillium roqueforti growing on malt extract agar was studied by correlating the produced heat (measured by isothermal calorimetry), ergosterol content (quantified by GC-MS/MS) and biomass of the mould at 10, 15, 20, 25 and 30°C. The results were analysed with a simple metabolic model from which the metabolic efficiency was calculated. The results show that the impact of temperature on growth rate and metabolic efficiency are different: although the mould fungus had the highest growth rate (in terms of thermal power, which was continuously measured) at 25°C, the substrate carbon conversion efficiency (biomass production divided by substrate consumption, both counted as moles carbon) was highest at 20°C. The temperature of the most rapid growth did therefore not equal the temperature of the most efficient growth.
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| 7. |
- Liu, Zhidan, et al.
(författare)
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Effects of inoculation strategy and cultivation approach on the performance of microbial fuel cell using marine sediment as bio-matrix
- 2008
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Ingår i: Journal of Applied Microbiology. - : Oxford University Press (OUP). - 1364-5072 .- 1365-2672. ; 104:4, s. 1163-1170
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Tidskriftsartikel (refereegranskat)abstract
- Aims: To investigate the effects of inoculation strategy and cultivation approach on the performance of microbial fuel cell (MFC). Methods and Results: A dual-chamber sediment fuel cell was set up fed with glucose under batch condition. At day 30, the supernatant consortium was partly transferred and used as inoculum for the evaluation of cultivation approach. Power output gradually increased to 9.9 mW m(-2) over 180 days, corresponding to coulombic efficiency (CE) of 29.6%. Separated biofilms attached anode enabled power output and CE dramatically up to 100.9 mW m(-2) and over 50%, respectively, whereas the residual sediment catalysed MFC gave a poor performance. MFC catalysed by in situ supernatant consortium demonstrated more than twice higher power than MFC catalysed by the supernatant consortium after Fe(OH)(3) cultivation. However, the re-generation of biofilms from the latter largely enhanced the cell performance. Conclusions: MFC exhibited a more efficient inducement of electroactive consortium than Fe(OH)(3) cultivation. MFC performance varied depending on different inoculation strategies. Significance and Impact of the Study: This is the first time to study cultivation approach affecting electricity generation. In addition, anodic limitations of mass and electron transfer were discussed through MFC catalysed by sediment-based bio-matrix.
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| 8. |
- Masurat, Peter, 1970, et al.
(författare)
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Identification of Meiothermus as the dominant genus in a storage system for spent nuclear fuel
- 2005
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Ingår i: Journal of Applied Microbiology. - : Oxford University Press (OUP). - 1364-5072 .- 1365-2672. ; 98:3, s. 727-740
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Tidskriftsartikel (refereegranskat)abstract
- Aims: To characterize the biofilms in an interim wet storage system (CLAB) for spent nuclear fuel. Methods and Results: Planktonic cells and biofilms were analysed with fluorescence microscopy, and scanning and transmission electron microscopy. The organisms in the biofilms were filamentous, consisting of sheaths with series of rod-shaped cells in them. Planktonic cell populations ranged between 1·4 × 103 and 5·2 × 103 ml-1, correlated with the system configuration, and was inversely correlated with total organic carbon (TOC) levels. Analysis of 16S rDNA indicated that a potentially novel Meiothermus sp. was dominant in the CLAB biofilms. A Meiothermus-specific probe was designed, and statistical analysis of fluorescence in situ hybridization results confirmed that Meiothermus sp. composed up to 98% of the biofilm. The low TOC levels (255 μg l-1) in the system combined with elevated water temperatures (ca 36°C) mimic the natural environments of Meiothermus sp. as well as the recommended conditions for isolating Meiothermus sp., thus supporting the results of the 16S rDNA analysis. Conclusions: A possibly novel Meiothermus sp. is the predominant genus found in the CLAB biofilms. Significance and Impact of the Study: TOC levels are often kept low to protect industrial systems from biofouling. However, the present study shows that, rather than protecting industrial systems against biofouling per se, maintaining low TOC levels might still result in biofilms, dominated by new, unknown bacterial species.
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| 9. |
- Pedersen, Karsten, 1952
(författare)
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Analysis of copper corrosion in compacted bentonite clay as a function of clay density and growth conditions for sulfate-reducing bacteria
- 2010
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Ingår i: Journal of Applied Microbiology. - : Oxford University Press (OUP). - 1364-5072 .- 1365-2672. ; 108:3, s. 1094-1104
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Tidskriftsartikel (refereegranskat)abstract
- Aims: This work investigated the relationships between sulfate-reducing bacteria (SRB), growth conditions, bentonite densities, and copper sulfide generation under circumstances relevant to underground, high-level radioactive waste repositories. Methods and Results: Experiments took place 450 m underground, connected under in situ pressure to groundwater containing SRB. The microbial reduction of sulfate to sulfide and subsequent corrosion of copper test plates buried in compacted bentonite were analysed using radioactive sulfur (35SO42−) as tracer. Mass distribution of copper sulfide on the plates indicated a diffusive process. The relationship between average diffusion coefficient (Ds) and tested density (ρ) was linear. Ds (m2 s−1) = −0.004 ×ρ (kg m−3) + 8.2, decreasing by 0.2 Ds units per 50 kg m−3 increase in density, from 1·2 × 10−11 m2 s−1 at 1750 kg m−3 to 0·2 × 10−11 m2 s−1 at 2000 kg m−3 Conclusions: Sulfide corrosion of waste canisters in future radioactive waste repositories likely depends mainly on sulfide concentration at the boundary between groundwater and the buffer, which in turn depends on SRB growth conditions (e.g., sulfate accessibility, carbon availability, and electron donors) and geochemical parameters (e.g., presence of ferrous iron, which immobilizes sulfide). Maintaining high bentonite density is also important in mitigating canister corrosion. Significance and impact of the study: The sulfide diffusion coefficients can be used in safety calculations regarding waste canister corrosion. The work supports findings that microbial activity in compacted bentonite will be restricted. The study emphasizes the importance of growth conditions for sulfate reduction at the groundwater boundary of the bentonite buffer and linked sulfide production.
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| 10. |
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