| 1. |
- Akerblom, Staffan, et al.
(författare)
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Experimentally induced effects of heavy metal on microbial activity and community structure of forest mor layers
- 2007
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Ingår i: Biology and Fertility of Soils. - : Springer Science and Business Media LLC. - 0178-2762 .- 1432-0789. ; 44:1, s. 79-91
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Tidskriftsartikel (refereegranskat)abstract
- This study compared the toxic effects of adding chromium (Cr), zinc (Zn), lead (Pb), molybdenum (Mo), nickel (Ni), and cadmium (Cd) at three dose levels to mor layer samples in laboratory experiments. Microbial activity in the form of soil respiration was monitored for 64 days. At the end of the experimental period, the composition of the soil microbial community structure was analysed by phospholipid fatty acid (PLFA) analysis. The metals added induced changes in the microbial community structure and affected respiration negatively, indicating toxicity. The microbial community structure (principal component analysis of the PLFA pattern) for all metals was significantly related to microbial activity (cumulative respiration), indicating intimate links between microbial community structure and activity. The most striking result in this study was that the shift in the microbial community because of metal stress was similar for all metals. Thus, the PLFA i16:0 increased most in relative abundance in metal-polluted soils, followed by other PLFAs indicative of Gram-positive bacteria (10Me16:0, 10Me17:0, 10Me18:0, a17:0 and br18:0). The PLFA 16:1 omega 5 was consistently negatively affected by metal stress, as were the PLFAs 18:1, 18:1 omega 7 and 19:1a. However, a significant separation between Cr- and Cd-polluted soils was observed in the response of the PLFA cy19:0, which decreased in abundance with Cr stress, and increased with Cd stress. Furthermore, the PLFA 18:2w6, indicating fungi, only increased with Cr and Zn stress. The effective doses of the metals, ranked with regard to background metal concentrations, decreased in the order: Zn > Cr > Pb > Mo > Ni > Cd. We concluded that interpretation of results of microbial activity from experiments of metal toxicity should include microbial structural patterns and background metal concentrations.
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| 2. |
- Aldén, Louise, et al.
(författare)
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Effects of sulfamethoxazole on soil microbial communities after adding substrate
- 2009
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Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 41:4, s. 840-848
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Tidskriftsartikel (refereegranskat)abstract
- The effect of the antibiotic sulfamethoxazole (SMX) on soil bacteria was studied using two methods (leucine incorporation and Biolog plates) of estimating pollution-induced community tolerance (PICT). SMX was added to an agricultural soil in a microcosm setup. The addition of different substrates (manure and alfalfa), and a non-amended soil, were also studied over 5 weeks. PICT measurements were validated by comparison with other measurements. Community structure was assessed using phospholipid fatty acid (PLFA) analysis and community-level physiological profiling (CLPP), and bacterial growth was estimated using leucine incorporation. Increased PICT was found at SMX concentrations of 20 and 500 mg SMX kg(-1) soil in samples containing manure and alfalfa, and at 500 mg SMX kg(-1) soil in non-amended soil (only concentration tested) using leucine incorporation. No effect was seen at 1 mg SMX kg(-1) soil. It was not necessary to add any substrate to increase the microbial activity in order to detect the effects of a bacteriostatic toxicant such as SMX when using measures based on bacterial growth. Direct inhibition of bacterial growth 2 days after SMX addition was correlated to PICT. No major changes in PICT due to SMX addition were found when using Biolog plates. However, there was a tendency towards increased PICT at the higher SMX concentrations in the manure-amended soil. Thus, different methods of detecting PICT have different sensitivities in detecting the toxic effects of SMX The effects of substrate amendment were reflected by changes in the microbial community, estimated using both PLEA and CLPP SMX was found to have a clear effect at the two highest levels of SMX in the manure- and alfalfa-amended soils, with an increase in fungal and a decrease in bacterial PLFAs. Little difference in the PLFA composition was found in the non-amended soil. CLPP was only affected at the highest SMX concentration. Although different variables showed different sensitivities to the effects of SMX, the results were consistent with an initial decrease in bacterial growth rates of sensitive species, which eventually transformed into more tolerant species, altering the community composition. (C) 2009 Elsevier Ltd. All rights reserved.
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| 3. |
- Aldén, Louise, et al.
(författare)
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No long-term persistence of bacterial pollution-induced community tolerance in tylosin-polluted soil
- 2008
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Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). - 1520-5851 .- 0013-936X. ; 42:18, s. 6917-6921
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Tidskriftsartikel (refereegranskat)abstract
- Pollution-induced community tolerance (PICT) of soil bacteria to the antibiotic tylosin was studied over 95 days. Tylosin was added at increasing concentrations, together with different amounts of alfalfa to study the effects of substrate addition on PICT and bacterial growth in soil. The leucine incorporation technique was used to estimate bacterial growth and as a detection method in the PICT concept. Direct inhibition of the bacterial growth rates, resulting in a dose-response curve, was found above 50 mg of tylosin kg(-1) of soil two days after tylosin addition (IC50 value of 960 mg tylosin kg(-1)). After 10 days of exposure to at least 50 mg of tylosin kg(-1), the PICT was observed and correlated to inhibition of bacterial growth by tylosin. A return of the PICT to control levels was found over time, and after 95 days at 1500 mg of tylosin kg(-1), essentially no PICT was found, as compared to the unpolluted control soil. The return of PICT to pre-exposure levels was not totally reflected in the recovery of bacterial growth. Alfalfa addition did not affect the inhibitory effect of tylosin on bacterial growth rates; neither did it alter the PICT. Since tylosin is relatively rapidly degraded in soil, our results indicate that the PICT will return to prepollution levels when the selective pressure of the toxicant is removed and will thus be a useful technique for monitoring remediation measures.
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| 4. |
- Aldén, Louise, et al.
(författare)
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The use of leucine incorporation to determine the toxicity of phenols to bacterial communities extracted from soil
- 2008
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Ingår i: Applied Soil Ecology. - : Elsevier BV. - 0929-1393. ; 38:1, s. 34-41
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Tidskriftsartikel (refereegranskat)abstract
- The toxicity of different phenols to the soil bacterial community was studied in the laboratory using the leucine incorporation technique. The effects of environmental factors such as pH, temperature and binding strength to soil particles were also assessed in order to deduce confounding effects due to the chemical and physical conditions in the soil from which the bacterial community was extracted. Bacterial growth varied with temperature and pH, the optima being at around 33 degrees C and pH 7 in a soil with a natural pH of 7. The toxicity of different phenols varied less than bacterial growth as a function of temperature and pH, but the toxicity of 2,3,6-trichlorophenol increased at lower temperatures and pH. The pH affected the toxicity in the same way in soils with naturally different pH values and when the pH was changed using buffers, showing that this was a direct effect of pH and was not due to different communities in different soils. The degree to which the bacteria were bound to soil particles had no effect on the toxicity of phenols. Neither did freezing nor thawing the soil have any effect on toxicity, although the bacterial growth was lower in frozen soil than in non-frozen soil. Increasing numbers of substitutes on the phenols increased their toxicity to soil bacteria, and chlorine substitutes were more toxic than the corresponding methyl substitutes. The toxicity of the phenols studied to the whole soil bacterial community was correlated with literature data on the toxicity to the single species Pseudomonas putida. Applying the leucine incorporation technique to the bacterial community extracted from soil was shown to be a rapid and sensitive method of estimating toxicity. The methodology also allowed differentiation between the effects of environmental factors on toxicity to the soil bacterial community and changes in the tolerance of the community. Thus, the development of pollution-induced community tolerance in phenol- and 2-chlorophenol-polluted soils could be shown. (c) 2007 Elsevier B.V. All rights reserved.
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| 5. |
- Aldén, Louise, et al.
(författare)
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Use of pollution-induced community tolerance of the bacterial community to detect phenol toxicity in soil.
- 2008
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Ingår i: Environmental Toxicology and Chemistry. - 0730-7268. ; 27:2, s. 334-340
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Tidskriftsartikel (refereegranskat)abstract
- Pollution-induced community tolerance (PICT) was used to study effects of phenol on soil bacteria. Phenol was added to an agricultural soil in a microcosm experiment. The effects were studied for up to four months. Bacterial growth rates were estimated with the leucine incorporation technique. This technique was also used as detection method for PICT. Changes in community structure were studied using the phospholipid fatty acid (PLFA) pattern. Increased phenol PICT of the bacterial community was found at phenol concentrations above 1 micromol/g wet weight soil. Direct inhibiting effect on bacterial growth rates 1 d after adding phenol was correlated to PICT. Phenol toxicity was reflected by changes in the structure of the bacterial community, although PICT appeared more sensitive than the PLFA method. In soil amended with 1 to 10 micromol phenol/g soil, bacterial growth recovered within one week. In the soil amended with the highest phenol concentration (30 micromol/g soil), bacterial growth rate recovered from total inhibition after 27 d, eventually reaching values six times higher than in the control. However, PICT did not change during the four months the experiment was performed. The specificity of PICT was also studied by examining cotolerance to 2-chlorophenol, 2,4-dichlorophenol, 2,3,6-trichlorophenol, Cu, and Zn. Adding phenol induced cotolerance of the bacterial community to the other phenols, although always at a lover level than to phenol. No cotolerance was found to metals in phenol-polluted soil. We conclude that the PICT concept is a valuable tool in determining phenol toxicity to bacterial communities, especially in situations where bacterial growth has recovered. Cotolerance between different phenols can, however, make interpretations of PICT more complicated.
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| 6. |
- Andréasson, Frida, et al.
(författare)
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Bioavailability of DOC in leachates, soil matrix solutions and soil water extracts from beech forest floors
- 2009
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Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 41:8, s. 1652-1658
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Tidskriftsartikel (refereegranskat)abstract
- The biodegradability of dissolved organic carbon (DOC) in different fractions from the forest floor was studied. Soil leachate (SI, the soil solution in macropores which is freely drained from forest floor after rainfall), the soil matrix solution (SMS, the soil solution in meso-/micropores of the soil matrix), and soil water extracts (SWE) from two different beech forest floors were compared. Zero-tension and tension lysimeters were used to collect SL and SMS, respectively. Loss of DOC (during 21 days) and respiration of CO2-C (during 7 days) were used as conventional measures of the availability of DOC. Bacterial production, measured using the leucine incorporation technique, and bacterial growth efficiency were also estimated. All methods were used to study differences in biodegradability between plots with and without ground flora (Deschampsia flexuosa or Anemone nemorosa) and different type of forest floor (with an organic (O) horizon or a mull (A) horizon). There were no differences in bioavailability of DOC from soil solutions extracted from plots with and without ground flora. The bioavailability of DOC in the different collected soil solutions varied, however. DOC in SWE was the most available, with a mean of 39% of DOC-loss in 21 days, and 18% of DOC being respired in 7 days. DOC in soil matrix solution was the least available of the soil solutions (7% respired), significantly less than DOC in soil leachate (11% respired). The methods measuring biodegradation of DOC, DOC-loss and CO2-C respiration gave similar results and were comparable to bacterial production and bacterial growth efficiency, with the exception of SWE from the O-horizon at the a flexuosa site, which had low bacterial production and bacterial growth efficiency, indicating a limitation of the bacterial growth. This study is one of the first to use bacterial production and bacterial growth efficiency for measuring bioavailability in terrestrial environments, giving an extra dimension for the process of biodegradation of DOC. (C) 2009 Elsevier Ltd. All rights reserved.
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| 7. |
- Barcenas-Moreno, Gema, et al.
(författare)
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Adaptation of soil microbial communities to temperature: comparison of fungi and bacteria in a laboratory experiment
- 2009
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013. ; 15:12, s. 2950-2957
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Tidskriftsartikel (refereegranskat)abstract
- Temperature not only has direct effects on microbial activity, but can also affect activity indirectly by changing the temperature dependency of the community. This would result in communities performing better over time in response to increased temperatures. We have for the first time studied the effect of soil temperature (5-50 degrees C) on the community adaptation of both bacterial (leucine incorporation) and fungal growth (acetate-in-ergosterol incorporation). Growth at different temperatures was estimated after about a month using a short-term assay to avoid confounding the effects of temperature on substrate availability. Before the experiment started, fungal and bacterial growth was optimal around 30 degrees C. Increasing soil temperature above this resulted in an increase in the optimum for bacterial growth, correlated to soil temperature, with parallel shifts in the total response curve. Below the optimum, soil temperature had only minor effects, although lower temperatures selected for communities growing better at the lowest temperature. Fungi were affected in the same way as bacteria, with large shifts in temperature tolerance at soil temperatures above that of optimum for growth. A simplified technique, only comparing growth at two contrasting temperatures, gave similar results as using a complete temperature curve, allowing for large scale measurements also in field situations with small differences in temperature.
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| 8. |
- Barcenas-Moreno, Gema, et al.
(författare)
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Bacterial and fungal growth in soil heated at different temperatures to simulate a range of fire intensities
- 2009
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Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 41:12, s. 2517-2526
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Tidskriftsartikel (refereegranskat)abstract
- The intensity of a fire is an important factor determining the recovery of soil microorganisms after a forest fire, since it can alter the quality and quantity of carbon sources. Recovery of the microbial community was studied in a Mediterranean pine forest soil subjected to different temperatures to simulate the short-term effects of fire intensity on bacterial and fungal growth, estimated using leucine incorporation for bacteria and acetate incorporation into ergosterol for fungi. Soil samples were heated for 15 min at 50, 80,120, 200, 300, 400 and 500 degrees C. After inoculation with fresh soil, and adding water to achieve 60% WHC, the soils were incubated at 20 degrees C for 21 days. Bacterial growth was initially inhibited in the samples heated above 50 degrees C (totally inhibited >= 200 degrees C), but recovered within days to levels much higher than the control, except for the samples heated at 500 degrees C, where growth remained low throughout the incubation period due to the destruction of most of the organic matter. After the first week of incubation, the bacterial response decreased to values close to, but still above, that of the control. Samples heated at 200 degrees C showed the highest cumulative bacterial growth. Fungal growth was initially lower than in the control in all the heated samples (totally inhibited >= 200 degrees C). Fungal growth recovered slowly during incubation in soils heated at <= 300 degrees C, but the cumulative growth in heated soils did not exceed that in the control. No fungal growth was observed in samples heated at the two highest temperatures. Soil respiration was initially totally inhibited in soil heated at >= 200 degrees C, but recovered rapidly in all soils; the highest respiration being observed already 1 day after inoculation. This is the first time both fungal and bacterial growth has been directly estimated in heated soils. High soil pH favouring bacteria can explain these results, but the differences in fungal and bacterial responses suggest a competitive interaction between these groups. (C) 2009 Elsevier Ltd. All rights reserved.
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| 9. |
- Bååth, Erland, et al.
(författare)
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Microbial Biomass, Community Structure and Metal Tolerance of a Naturally Pb-Enriched Forest Soil
- 2005
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Ingår i: Microbial Ecology. - : Springer Science and Business Media LLC. - 1432-184X .- 0095-3628. ; 50:4, s. 496-505
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The effect of long-term elevated soil Pb levels on soil microbiota was studied at a forest site in Norway, where the soil has been severely contaminated with Pb since the last period of glaciation (several thousand years). Up to 10% Pb (total amount, w/w) has been found in the top layer. The microbial community was drastically affected, as judged from changes in the phospholipid fatty acid (PLFA) pattern. Specific PLFAs that were high in Pb-enriched soil were branched (especially br17:0 and br18:0), whereas PLFAs common in eukaryotic organisms such as fungi (18:2ω6,9 and 20:4) were low compared with levels at adjacent, uncontaminated sites. Congruent changes in the PLFA pattern were found upon analyzing the culturable part of the bacterial community. The high Pb concentrations in the soil resulted in increased tolerance to Pb of the bacterial community, measured using both thymidine incorporation and plate counts. Furthermore, changes in tolerance were correlated to changes in the community structure. The bacterial community of the most contaminated soils showed higher specific activity (thymidine and leucine incorporation rates) and higher culturability than that of control soils. Fungal colony forming units (CFUs) were 10 times lower in the most Pb-enriched soils, the species composition was widely different from that in control soils, and the isolated fungi had high Pb tolerance. The most commonly isolated fungus in Pb-enriched soils was Tolypocladium inflatum. Comparison of isolates from Pb-enriched soil and isolates from unpolluted soils showed that T. inflatum was intrinsically Pb-tolerant, and that the prolonged conditions with high Pb had not selected for any increased tolerance.
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| 10. |
- de Vries, Franciska T., et al.
(författare)
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High turnover of fungal hyphae in incubation experiments
- 2009
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Ingår i: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 1574-6941 .- 0168-6496. ; 67:3, s. 389-396
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Tidskriftsartikel (refereegranskat)abstract
- Soil biological studies are often conducted on sieved soils without the presence of plants. However, soil fungi build delicate mycelial networks, often symbiotically associated with plant roots (mycorrhizal fungi). We hypothesized that as a result of sieving and incubating without plants, the total fungal biomass decreases. To test this, we conducted three incubation experiments. We expected total and arbuscular mycorrhizal (AM) fungal biomass to be higher in less fertilized soils than in fertilized soils, and thus to decrease more during incubation. Indeed, we found that fungal biomass decreased rapidly in the less fertilized soils. A shift towards thicker hyphae occurred, and the fraction of septate hyphae increased. However, analyses of phospholipid fatty acids (PLFAs) and neutral lipid fatty acids could not clarify which fungal groups were decreasing. We propose that in our soils, there was a fraction of fungal biomass that was sensitive to fertilization and disturbance (sieving, followed by incubation without plants) with a very high turnover (possibly composed of fine hyphae of AM and saprotrophic fungi), and a fraction that was much less vulnerable with a low turnover (composed of saprotrophic fungi and runner hyphae of AMF). Furthermore, PLFAs might not be as sensitive in detecting changes in fungal biomass as previously thought.
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