| 1. |
- Kolb, Gundula S., et al.
(author)
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Effects of Nesting Cormorants (Phalacrocorax carbo) on Soil Chemistry, Microbial Communities and Soil Fauna
- 2015
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In: Ecosystems. - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; 18:4, s. 643-657
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Journal article (peer-reviewed)abstract
- Seabirds act as vectors transporting marine nutrients to land by feeding on fish while nesting and roosting on islands. By depositing large amounts of nutrient-rich guano on their nesting islands they strongly affect island soils, vegetation and consumers. However, few studies have investigated how nesting seabirds affect soil communities. In this study, we investigated how cormorant nesting colonies affect soil chemistry, soil microbes and soil and litter fauna on their nesting islands in the Stockholm archipelago, Sweden. We found that cormorant colonies strongly increase organic soil N and P concentrations, and the effect is stronger close to cormorant nests. Microbial communities were studied by extracting phospholipid fatty acids (PLFA) from the soil. The total amounts of PLFA and the amount of PLFA indicating bacterial biomass were lower on active cormorant islands than on reference islands. Furthermore, PLFA structure and thus microbial community structure differed between cormorant and reference islands. Among ten investigated soil and litter arthropod groups three groups (Thysanoptera, Araneae and Oribatida) showed lower densities and one group (Astigmata) showed higher densities in soils on active cormorant than on reference islands. Some arthropod groups showed strong spatial variation on the cormorant islands. Astigmata, Mesostigmata and Diptera showed higher densities in soil samples close to cormorant nests, whereas Oribatida, Collembola and Hemiptera showed lower densities in litter samples close to cormorant nests than in samples taken 3-20 m away from nests. Overall, the cormorant colonies strongly affected soil ecosystems of their nesting islands, but causal correlations between arthropod densities and soil factors were difficult to reveal. One likely reason may be that nesting cormorant islands are very heterogeneous habitats showing large spatial variation in both soil properties as well as fauna densities.
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| 2. |
- Milenkovski, Susann, et al.
(author)
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Toxicity of fungicides to natural bacterial communities in wetland water and sediment measured using leucine incorporation and potential denitrification
- 2010
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In: ECOTOXICOLOGY. - : Springer Science and Business Media LLC. - 0963-9292 .- 1573-3017. ; 19:2, s. 285-294
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Journal article (peer-reviewed)abstract
- We assessed potential toxicity of fungicides to natural bacterial communities from a constructed wetland, located in southern Sweden, and compared the sensitivity of two endpoints indicating bacterial activity, leucine incorporation, and potential denitrification, in detecting toxicity. The effects of eight fungicides (benomyl, carbendazim, carboxin, captan, cycloheximide, fenpropimorph, propiconazole, and thiram), two bactericides (bronopol and chlortetracycline) as controls, and one reference compound (3,5-dichlorophenol), were tested in a water-sediment microcosm set-up. Leucine incorporation was measured in both the water and sediment column, while potential denitrification was measured for the entire microcosm. The bactericides and the reference compound gave sigmoid concentration-response curves for both endpoints in all but one case. The fungicides thiram, captan, and benomyl, and to a lesser extent fenpropimorph and propiconazole had quantifiable toxic effects on leucine incorporation, with EC50 values ranging from 3 to 70 mg l(-1), while carbendazim, carboxin, and cycloheximide had little effect at the investigated concentrations. Only thiram and captan inhibited potential denitrification; the other fungicides showed no quantifiable effect. A greater toxic effect on leucine incorporation was recorded for bacterial communities associated with the water column, compared to the sediment column, for all tested compounds. Leucine incorporation was the more sensitive method for toxicity assessment of bacterial communities, and also allowed for a rapid and simple way of comparing exposure in the sediment and water column, making it an attractive standard method for community based toxicological assays in aquatic environments.
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| 3. |
- Olsson, Pål Axel, et al.
(author)
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Phosphorus effects on the mycelium and storage structures of an arbuscular mycorrhizal fungus as studied in the soil and roots by analysis of fatty acid signatures
- 1997
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In: Applied and Environmental Microbiology. - 0099-2240. ; 63:9, s. 3531-3538
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Journal article (peer-reviewed)abstract
- The distribution of an arbuscular mycorrhizal (AM) fungus between soil and roots, and between mycelial and storage structures, was studied by use of the fatty acid signature 16:1(omega)5. Increasing the soil phosphorus level resulted in a decrease in the level of the fatty acid 16:1(omega)5 in the soil and roots. A similar decrease was detected by microscopic measurements of root colonization and of the length of AM fungal hyphae in the soil. The fatty acid 16:1(omega)5 was estimated from two types of lipids, phospholipids and neutral lipids, which mainly represent membrane lipids and storage lipids, respectively. The numbers of spores of the AM fungus formed in the soil correlated most closely with neutral lipid fatty acid 16:1(omega)5, whereas the hyphal length in the soil correlated most closely with phospholipid fatty acid 16:1(omega)5. The fungal neutral lipid/phospholipid ratio in the extraradical mycelium was positively correlated with the level of root infection and thus decreased with increasing applications of P. The neutral lipid/phospholipid ratio indicated that at high P levels, less carbon was allocated to storage structures. At all levels of P applied, the major part of the AM fungus was found to be present outside the roots, as estimated from phospholipid fatty acid 16:1(omega)5. The ratio of extraradical biomass/intraradical biomass was not affected by the application of P, except for a decrease at the highest level of P applied.
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| 4. |
- Söderberg, Katarina, et al.
(author)
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Structure and activity of the bacterial community in the rhizosphere of different plant species and the effect of arbuscular mycorrhizal colonisation
- 2002
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In: FEMS Microbiology Ecology. - 1574-6941. ; 40:3, s. 223-231
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Journal article (peer-reviewed)abstract
- The aim of this study was to determine if arbuscular mycorrhizal (AM) colonisation influences rhizosphere bacteria differently depending on plant species. Thus, the effect of AM colonisation (Glomus intraradices) on rhizosphere bacteria of subterranean clover, cucumber, leek and maize was studied. The bacterial activity was measured as thymidine or leucine incorporation and bacterial numbers as colony forming units and acridine orange direct counts. The phospholipid fatty acid (PLFA) pattern was used to characterise the bacterial community structure and was compared with the community substrate utilisation pattern using Biolog. The bacterial activity and bacterial densities differed between the rhizospheres of the plant species. AM colonisation had a low impact on bacterial activity, but affected bacterial numbers differently depending on the plant species. Only small effects of AM colonisation were detected with the PLFA technique, and no effects were seen with Biolog, while similar effects of the plant species were found for these techniques. Thus, the plant species had greater effects on the bacterial community in the rhizosphere than AM colonisation and the effect of AM differed between plant species. (C) 2002 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.
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| 5. |
- Törneman, Niklas, et al.
(author)
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Spatial covariation of microbial community composition and polycyclic aromatic hydrocarbon concentration in a creosote-polluted soil
- 2008
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In: Environmental Toxicology and Chemistry. - : Wiley. - 0730-7268 .- 1552-8618. ; 27:5, s. 1039-1046
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Journal article (peer-reviewed)abstract
- Little is known about the spatial connection between soil microbial community composition and polycyclic aromatic hydrocarbon (PAH) concentration. A spatially explicit survey at a creosote-contaminated site demonstrated that microbial biomass (total concentration of phospholipid fatty acids [PLFAs]) and microbial community composition (PLFA fingerprints) were spatially autocorrelated, mostly within a distance of 25 m, and covaried with PAH concentrations. The concentration of PLFAs indicative of gram-negative bacteria (16:1 omega 7c, 16:1 omega 7t, 18:1 omega 7, cy17:0, and cy19:0) increased in the PAH hot spots, whereas PLFAs representing fungi and gram-positive bacteria (including actinomycetes) were negatively correlated to PAH concentrations. Most PLFAs were spatially autocorrelated, with distances varying between 4 and 25 m. Those PLFAs that increased in PAH-contaminated soil had autocorrelation ranges between 4 and 16 m, whereas the fungal indicator PLEA 18:2 omega 6,9 had the largest autocorrelation range (25 in). Bacterial strains isolated using a spray-plate technique and with the same PLFA composition as that in contaminated soil samples were capable of degrading phenanthrene, fluoranthene, and pyrene, indicating that the main PAH degraders could be isolated.
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| 6. |
- Bååth, Erland, et al.
(author)
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Temperature Adaptation of Aquatic Bacterial Community Growth Is Faster in Response to Rising than to Falling Temperature
- 2024
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In: Microbial Ecology. - 0095-3628. ; 87
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Journal article (peer-reviewed)abstract
- Bacteria are key organisms in energy and nutrient cycles, and predicting the effects of temperature change on bacterial activity is important in assessing global change effects. A changing in situ temperature will affect the temperature adaptation of bacterial growth in lake water, both long term in response to global change, and short term in response to seasonal variations. The rate of adaptation may, however, depend on whether temperature is increasing or decreasing, since bacterial growth and turnover scale with temperature. Temperature adaptation was studied for winter (in situ temperature 2.5 °C) and summer communities (16.5 °C) from a temperate lake in Southern Sweden by exposing them to a temperature treatment gradient between 0 and 30 °C in ~ 5 °C increments. This resulted mainly in a temperature increase for the winter and a decrease for the summer community. Temperature adaptation of bacterial community growth was estimated as leucine incorporation using a temperature Sensitivity Index (SI, log growth at 35 °C/4 °C), where higher values indicate adaptation to higher temperatures. High treatment temperatures resulted in higher SI within days for the winter community, resulting in an expected level of community adaptation within 2 weeks. Adaptation for the summer community was also correlated to treatment temperature, but the rate of adaption was slower. Even after 5 weeks, the bacterial community had not fully adapted to the lowest temperature conditions. Thus, during periods of increasing temperature, the bacterial community will rapidly adapt to function optimally, while decreasing temperature may result in long periods of non-optimal functioning.
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| 7. |
- Fernández-Calviño, David, et al.
(author)
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Ecotoxicological assessment of propiconazole using soil bacterial and fungal growth assays
- 2017
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In: Applied Soil Ecology. - : Elsevier BV. - 0929-1393. ; 115, s. 27-30
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Journal article (peer-reviewed)abstract
- Effects of the fungicide propiconazole on soil microorganisms were tested using [3H] leucine incorporation and [14C] acetate in ergosterol incorporation to measure bacterial and fungal growth inhibition, respectively. Growth was compared to basal respiration (BR) and substrate-induced respiration (SIR) in soil microcosms established according to the OECD 217 guideline. Fungal growth was most sensitive with IC50 values remaining around 300 mg kg−1 during 40 days of incubation. SIR was initially less sensitive (IC50 1300 mg kg−1), but IC50 values progressively decreased over time to reach 380 mg kg−1 after 40 days. Bacterial growth was affected at concentrations ≥200 mg kg−1, but exhibited more complex dose-response relationships possibly due to a combination of direct toxicity, bacterial community adaptation, and competitive release from the more severely affected fungi. BR was either stimulated or not affected by propiconazole. Our results indicate that group-specific endpoints targeting microbial growth will improve ecotoxicological assessment of toxicants for environmental risk assessment.
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| 8. |
- Meisner, Annelein, et al.
(author)
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Partial drying accelerates bacterial growth recovery to rewetting
- 2017
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In: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717. ; 112, s. 269-276
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Journal article (peer-reviewed)abstract
- Fluctuations in soil moisture create drying-rewetting events affecting the activity of microorganisms. Microbial responses to drying-rewetting are mostly studied in soils that are air-dried before rewetting. Upon rewetting, two patterns of bacterial growth have been observed. In the Type 1 pattern, bacterial growth rates increase immediately in a linear fashion. In the Type 2 pattern, bacterial growth rates increase exponentially after a lag period. However, soils are often only partially dried. Partial drying (higher remaining moisture content before rewetting) may be considered a less harsh treatment compared with air-drying. We hypothesized that a soil with a Type 2 response upon rewetting air-dried soil would transform into a Type 1 response if dried partially before rewetting. Two soils were dried to a gradient of different moisture content. Respiration and bacterial growth rates were then measured before and during 48 h after rewetting to 50% of water holding capacity (WHC). Initial moisture content determined growth and respiration in a sigmoidal fashion, with lowest activity in air-dried soil and maximum above ca. 30% WHC. Partial drying resulted in shorter lag periods, shorter recovery times and lower maximum bacterial growth rates after rewetting. The respiration after rewetting was lower when soil was partially dried and higher when soils were air-dried. The threshold moisture content where transition from a Type 2 to a Type 1 response occurred was about 14% WHC, while >30% WHC resulted in no rewetting effect. We combine our result with other recent reports to propose a framework of response patterns after drying-rewetting, where the harshness of drying determines the response pattern of bacteria upon rewetting dried soils.
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| 9. |
- Arnebrant, Kristina, et al.
(author)
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Measurements of ATP in forest humus
- 1991
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In: Soil Biology & Biochemistry. - 0038-0717. ; 23:6, s. 501-506
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Journal article (peer-reviewed)abstract
- The measurement of ATP as an estimate of microbial biomass C in humus was studied. Three different acid extractants, H2SO4, TCA and H3PO4 were compared, as well as two different buffers, Tris and arsenate. No difference in extraction efficiency was found when the light output was converted to ATP content using internal ATP standards, but the different extraction agents and buffers influenced the light output. Several pretreatments and storage conditions were investigated. Incubation at 25°C for 1–7 days gave ca 50% higher ATP values than incubation at 4°C. Sieving did not affect the result. For long-term storage of humus, 4°C is recommended instead of freezing, since freezing reduced the ATP content to ca 80% of the amount found in humus stored at 4°C after 2 months. Freezing of the humus extract resulted in even larger losses of ATP. Humus from eight coniferous forests in Sweden was investigated with respect to ATP content and microbial biomass, estimated with the substrate induced respiration rate method (SIR). A close linear relationship (r = 0.95) was found between the two types of measurement. Calculated from this relationship the amount of ATP (at 25°C) was 3.2μmg−1 biomass C.
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| 10. |
- Aira, Manuel, et al.
(author)
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Plant genotype strongly modifies the structure and growth of maize rhizosphere microbial communities
- 2010
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In: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 42:12, s. 2276-2281
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Journal article (peer-reviewed)abstract
- We studied the microbial communities in maize (Zea mays) rhizosphere to determine the extent to which their structure, biomass, activity and growth were influenced by plant genotype (su1 and sh2 genes) and the addition of standard and high doses of different types of fertilizer (inorganic, raw manure and vermicompost). For this purpose, we sampled the rhizosphere of maize plants at harvest, and analyzed the microbial community structure (PLFA analysis) and activity (basal respiration and bacterial and fungal growth rates). Discriminant analysis clearly differentiated rhizosphere microbial communities in relation to plant genotype. Although microorganisms clearly responded to dose of fertilization, the three fertilizers also contributed to differentiate rhizosphere microbial communities. Moreover, larger plants did not promoted higher biomass or microbial growth rates suggesting complex interactions between plants and fertilizers, probably as a result of the different performance of plant genotypes within fertilizer treatments, i.e. differences in the quality and/or composition of root exudates. (c) 2010 Elsevier Ltd. All rights reserved.
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