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  • 1
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    Flux of Root-Derived Carbon into the Nematode Micro-Food Web: A Comparison of Grassland and Agroforest (2022)
    Berlin : Humboldt-Universität zu Berlin
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    UID:
    edochu_18452_25206
    Format: 1 Online-Ressource (17 Seiten)
    Content: Carbon (C) cycling is crucial to agroecosystem functioning. Important determinants for the belowground C flow are soil food webs, with microorganisms and microfaunal grazers, i.e., nematodes, as key biota. The present study investigates the incorporation of plant-derived C into the nematode micro-food web under two different cropping systems, grassland (ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.)) and agroforest (willow (Salix schwerinii Wolf and Salix viminalis L)). To quantify the C flux from the plant into the soil micro-food web, grass and willow were pulse-labeled with 13CO2 and the incorporation of 13C into the nematode trophic groups was monitored 3, 7, 14 and 28 days after labeling. The natural stable isotope signals (13C/12C, 15N/14N) were analyzed to determine the structure of the nematode micro-food web. The natural isotopic δ15N signal revealed different trophic levels for omnivores and predators in grassland and agroforest soils. The incorporation of plant C into nematode tissue was detectable three days after 13CO2 labeling with the highest and fastest C allocation in plant feeders in grassland, and in fungal feeders in agroforest soil. C flux dynamics between the aboveground vegetation and belowground micro-food web varied with cropping system. This demonstrates that crop-specific translocation of C affects the multitrophic interactions in the root environment, which in turn can alter soil nutrient cycling.
    Content: Peer Reviewed
    Note: This article was supported by the German Research Foundation (DFG) and the Open Access Publication Fund of Humboldt-Universität zu Berlin.
    In: Agronomy, Basel : MDPI, 12,2022,4
    Language: English
    DOI: 10.18452/24536
    URN: urn:nbn:de:kobv:11-110-18452/25206-4
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  • 2
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    Improving the application of quantitative fatty acid signature analysis in soil food webs: The effects of diet fat content (2021)
    Berlin : Humboldt-Universität zu Berlin
    Details
    UID:
    edochu_18452_25225
    Format: 1 Online-Ressource (12 Seiten)
    Content: Quantitative fatty acid signature analysis (QFASA) as a biochemical tool to study the diet composition of predators is frequently used in marine ecology to infer trophic links in vertebrate consumers. However, the potential and challenges of this method in other ecosystems have only recently been studied. The application in soil ecosystems leads to hurdles not encountered in the marine, such as the low similarity of fatty acid signatures between resource and consumer. So far, diet estimation attempts have been semisuccessful, necessitating to adapt QFASA for use in soil food webs. Dietary fat content may play an important role, as it influences consumer metabolism, and thus calibration coefficients for fatty acid trophic transfer. A series of feeding trials with baker's yeast spiked with five different pure fatty acids at various concentrations was conducted with Collembola, and the changes in calibration coefficients were observed. From there, equations were gained through regression analysis and new sets of calibration coefficients were calculated. QFASA was applied on a range of basal resources and the results compared with previously defined calibration coefficients. Calibration coefficients changed with the proportion of fatty acids in the diet and differed between the three Collembolan species. The re-estimation of diets showed an improvement of model performance by the new calibration coefficients and indicated several modes of fatty acid assimilation. These greatly influence the outcome of diet estimation, for example, algal and bacterial diets are likely underestimated due to high metabolic turnover rates. The application of QFASA in soil ecosystems remains challenging. The variation in calibration coefficients and the resulting decrease in estimation deviation indicate the merit of calculating calibration coefficients from consumer signatures through linear or exponential equations. Ideally, the method should, when extended to the entire fatty acid signature, allow correct determination of consumer diets in soil food webs.
    Content: Peer Reviewed
    Note: This article was supported by the German Research Foundation (DFG) and the Open Access Publication Fund of Humboldt-Universität zu Berlin.
    In: Ecology and evolution Erschienen, : John Wiley & Sons, Inc., 11,2021,16, Seiten 11065-11076
    Language: English
    DOI: 10.18452/24553
    URN: urn:nbn:de:kobv:11-110-18452/25225-9
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  • 3
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    Essential Biomolecules in Food Webs (2019)
    Berlin : Humboldt-Universität zu Berlin
    Details
    UID:
    edochu_18452_20932
    Format: 1 Online-Ressource (18 Seiten)
    ISSN: 2296-701X , 2296-701X
    Content: We here review the ecological role of essential nutritional biomolecules [fatty acids (FA), amino acids (AA), sterols, vitamins] in aquatic and terrestrial food webs, encompassing the forces behind their environmental distribution. Across ecosystems, mutualistic relationships frequently ensure exchanges of vitamins between producer and demander, especially between B12 and other B vitamins as well as the AA methionine. In contrast, FA, sterols and most AA are transferred up the food chain via classical predatorprey interactions, and therefore have good biomarker potential for trophic interactions. As biomass-flow depends on the absolute amounts of potential limiting resources, considering solely the relative share in the respective biochemical group may underor overestimate the availability to consumers. Moreover, if not accounted for, “hidden” trophic channels, such as gut symbionts as well as metabolic conversion of precursor molecules, can hamper food web analyses. Fundamental differences exist between aquatic and terrestrial ecosystems: Vitamin B12 produced by ammonium oxidizing Archaea is essential to many aquatic algae, whereas terrestrial plants escaped this dependency by using B12 independent enzymes. Long-chain &3 polyunsaturated FA (LC-&3PUFA) in aquatic systemsmainly originate fromplanktonic algae, while in terrestrial systems, belowground invertebrates can well be a source, also supporting aboveground biota. Interlinks from terrestrial to aquatic ecosystems are of a biochemically totally different nature than vice versa. While biomass rich in proteins and LC-&3PUFA is transferred to land, e.g., by trophic relationships, the link from terrestrial to aquatic ecosystems provides recalcitrant plant carbon, mainly devoid of essential nutrients, fuelling detrital food chains. Recent global changes influence food webs via altered input and transfer of essential biomolecules, but separating the effects of nutrients, CO2, and warming is not trivial. Current evolutionary concepts (e.g., Black Queen, relaxed selection) considering the costs of metabolic production partly explain food web dynamics, especially for vitamins, whereas adaptations to potential oxidative stress seemto bemore important for LC-PUFA. Overall, the provision with essential biomolecules is precious for both heterotrophs and auxotrophs. These nutritional valuable molecules often are kept unaltered in consumer metabolism, including their stable isotope composition, offering a great advantage for their use as trophic markers.
    Content: Peer Reviewed
    Note: This article was supported by the German Research Foundation (DFG) and the Open Access Publication Fund of Humboldt-Universität zu Berlin.
    In: Frontiers in Ecology and Evolution, Lausanne : Frontiers Media, 7,2019, 2296-701X
    Language: English
    DOI: 10.18452/20183
    URN: urn:nbn:de:kobv:11-110-18452/20932-3
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  • 4
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    Editorial: Essential Biomolecules Caught in the Food Web? (2019)
    Berlin : Humboldt-Universität zu Berlin
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    UID:
    edochu_18452_23417
    Format: 1 Online-Ressource (3 Seiten)
    Content: Peer Reviewed
    In: Frontiers in Ecology and Evolution, Lausanne : Frontiers Media S.A., 7,2019
    Language: English
    DOI: 10.3389/fevo.2019.00471
    DOI: 10.18452/22770
    URN: urn:nbn:de:kobv:11-110-18452/23417-6
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  • 5
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    Toxicity Assay for Citrinin, Zearalenone and Zearalenone-14-Sulfate Using the Nematode Caenorhabditis elegans as Model Organism (2018)
    Berlin : Humboldt-Universität zu Berlin
    Details
    UID:
    edochu_18452_21154
    Format: 1 Online-Ressource (12 Seiten)
    Content: To keep pace with the rising number of detected mycotoxins, there is a growing need for fast and reliable toxicity tests to assess potential threats to food safety. Toxicity tests with the bacterial-feeding nematode Caenorhabditis elegans as the model organism are well established. In this study the C. elegans wildtype strain N2 (var. Bristol) was used to investigate the toxic effects of the food-relevant mycotoxins citrinin (CIT) and zearalenone-14-sulfate (ZEA-14-S) and zearalenone (ZEA) on different life cycle parameters including reproduction, thermal and oxidative stress resistance and lifespan. The metabolization of the mycotoxins by the nematodes in vivo was investigated using HPLC-MS/MS. ZEA was metabolized in vivo to the reduced isomers α-zearalenol (α-ZEL) and β-ZEL. ZEA-14-S was reduced to α-/β-ZEL-14-sulfate and CIT was metabolized to mono-hydroxylated CIT. All mycotoxins tested led to a significant decrease in the number of nematode offspring produced. ZEA and CIT displayed negative effects on stress tolerance levels and for CIT an additional shortening of the mean lifespan was observed. In the case of ZEA-14-S, however, the mean lifespan was prolonged. The presented study shows the applicability of C. elegans for toxicity testing of emerging food mycotoxins for the purpose of assigning potential health threats.
    Content: Peer Reviewed
    In: Toxins, Basel : MDPI, 10,2018,7, Seiten 284/1-284/12
    Language: English
    DOI: 10.3390/toxins10070284
    DOI: 10.18452/20404
    URN: urn:nbn:de:kobv:11-110-18452/21154-3
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  • 6
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    Micro-Food Web Structure Shapes Rhizosphere Microbial Communities and Growth in Oak (2018)
    Berlin : Humboldt-Universität zu Berlin
    Details
    UID:
    edochu_18452_21131
    Format: 1 Online-Ressource (16 Seiten)
    Content: The multitrophic interactions in the rhizosphere impose significant impacts on microbial community structure and function, affecting nutrient mineralisation and consequently plant performance. However, particularly for long-lived plants such as forest trees, the mechanisms by which trophic structure of the micro-food web governs rhizosphere microorganisms are still poorly understood. This study addresses the role of nematodes, as a major component of the soil micro-food web, in influencing the microbial abundance and community structure as well as tree growth. In a greenhouse experiment with Pedunculate Oak seedlings were grown in soil, where the nematode trophic structure was manipulated by altering the proportion of functional groups (i.e., bacterial, fungal, and plant feeders) in a full factorial design. The influence on the rhizosphere microbial community, the ectomycorrhizal symbiont Piloderma croceum, and oak growth, was assessed. Soil phospholipid fatty acids were employed to determine changes in the microbial communities. Increased density of singular nematode functional groups showed minor impact by increasing the biomass of single microbial groups (e.g., plant feeders that of Gram-negative bacteria), except fungal feeders, which resulted in a decline of all microorganisms in the soil. In contrast, inoculation of two or three nematode groups promoted microbial biomass and altered the community structure in favour of bacteria, thereby counteracting negative impact of single groups. These findings highlight that the collective action of trophic groups in the soil micro-food web can result in microbial community changes promoting the fitness of the tree, thereby alleviating the negative effects of individual functional groups.
    Content: Peer Reviewed
    In: Diversity, Basel : MDPI, 10,2018,1, Seiten 15/1-15/16
    Language: English
    DOI: 10.3390/d10010015
    DOI: 10.18452/20380
    URN: urn:nbn:de:kobv:11-110-18452/21131-4
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  • 7
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    Microplastics Effects on Reproduction and Body Length of the Soil-Dwelling Nematode Caenorhabditis elegans (2020)
    Berlin : Humboldt-Universität zu Berlin
    Details
    UID:
    edochu_18452_23086
    Format: 1 Online-Ressource (9 Seiten)
    Content: Microplastics (MP) are pervasive in the environment. There is ample evidence of negative MP effects on biota in aquatic ecosystems, though little is known about MP effects in terrestrial ecosystems. Given numerous entry routes of MP into soils, soil organisms are likely to be exposed to MP. We compared potential toxicological effects of MP from (i) low-density polyethylene (LDPE) (mean diameter ± standard deviation: 57 ± 40 μm) and (ii) a blend of biodegradable polymers polylactide (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) (40 ± 31 μm) on the reproduction and body length of the soil-dwelling bacterivorous nematode Caenorhabditis elegans. Feed suspensions without (control) or with MP (treatments) at concentrations of 1, 10, and 100 mg MP L–1 were prepared and nematodes were exposed to those suspensions on agar plates until completion of their reproductive phase (∼6 days). Using Nile red-stained PLA/PBAT MP particles and fluorescence microscopy, we demonstrated the ingestion of MP by C. elegans into pharynges and intestines. Under MP exposure, nematodes had fewer offspring (up to 22.9%) compared to nematodes in the control group. This decline was independent on the plastic type. We detected a tendency toward greater decreases in offspring at higher concentrations. Despite hints of negative effects on nematode body length under MP exposure, we could not derive a consistent pattern. We conclude that in MP-contaminated soils, the reproduction of nematodes, central actors in the soil food web, can be affected, with potentially negative implications for key soil functions, e.g., the regulation of soil biogeochemical cycles.
    Content: Peer Reviewed
    In: Lausanne : Frontiers Media S.A., 8
    Language: English
    DOI: 10.3389/fenvs.2020.00041
    DOI: 10.18452/22474
    URN: urn:nbn:de:kobv:11-110-18452/23086-8
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  • 8
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    Legionella pneumophila and Free-Living Nematodes: Environmental Co-Occurrence and Trophic Link (2023)
    Berlin : Humboldt-Universität zu Berlin
    Details
    UID:
    edochu_18452_27144
    Format: 1 Online-Ressource (20 Seiten)
    Content: Free-living nematodes harbor and disseminate various soil-borne bacterial pathogens. Whether they function as vectors or environmental reservoirs for the aquatic L. pneumophila, the causative agent of Legionnaires’ disease, is unknown. A survey screening of biofilms of natural (swimming lakes) and technical (cooling towers) water habitats in Germany revealed that nematodes can act as potential reservoirs, vectors or grazers of L. pneumophila in cooling towers. Consequently, the nematode species Plectus similis and L. pneumophila were isolated from the same cooling tower biofilm and taken into a monoxenic culture. Using pharyngeal pumping assays, potential feeding relationships between P. similis and different L. pneumophila strains and mutants were examined and compared with Plectus sp., a species isolated from a L. pneumophila-positive thermal source biofilm. The assays showed that bacterial suspensions and supernatants of the L. pneumophila cooling tower isolate KV02 decreased pumping rate and feeding activity in nematodes. However, assays investigating the hypothesized negative impact of Legionella’s major secretory protein ProA on pumping rate revealed opposite effects on nematodes, which points to a species-specific response to ProA. To extend the food chain by a further trophic level, Acanthamoebae castellanii infected with L. pneumphila KV02 were offered to nematodes. The pumping rates of P. similis increased when fed with L. pneumophila-infected A. castellanii, while Plectus sp. pumping rates were similar when fed either infected or non-infected A. castellanii. This study revealed that cooling towers are the main water bodies where L. pneumophila and free-living nematodes coexist and is the first step in elucidating the trophic links between coexisting taxa from that habitat. Investigating the Legionella–nematode–amoebae interactions underlined the importance of amoebae as reservoirs and transmission vehicles of the pathogen for nematode predators.
    Content: Peer Reviewed
    In: : MDPI, 11,3
    Language: English
    DOI: 10.3390/microorganisms11030738
    DOI: 10.18452/26467
    URN: urn:nbn:de:kobv:11-110-18452/27144-1
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  • 9
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    Soil Nematodes as a Means of Conservation of Soil Predatory Mites for Biocontrol (2022)
    Berlin : Humboldt-Universität zu Berlin
    Details
    UID:
    edochu_18452_27461
    Format: 1 Online-Ressource (27 Seiten)
    Content: Numerous lab and field studies have reported the potential of soil predatory mites for the biological control of plant-parasitic nematodes and arthropods pests. Most of these studies have utilized biocontrol agents in augmentative releases, essentially controlling the pest with the released predators. While this may be a valid approach, we hypothesize that conservation of soil mite predators with available, suitable, and accessible free-living nematodes as prey, will provide better agricultural ecosystem performance and long-range sustainability. In this manuscript, we review the relevant studies on soil predatory mite–nematode interactions and highlight their potential for conservation biological control of soil-borne pests. Additionally, we emphasize the importance of implementing environmentally sound soil management practices for the sustainability and conservation of functional soil food webs.
    Note: This article was supported by the German Research Foundation (DFG) and the Open Access Publication Fund of Humboldt-Universität zu Berlin.
    In: Basel : MDPI, 13,1
    Language: English
    DOI: 10.18452/26775
    DOI: 10.3390/agronomy13010032
    URN: urn:nbn:de:kobv:11-110-18452/27461-1
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  • 10
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    Ectomycorrhizal fungus supports endogenous rhythmic growth and corresponding resource allocation in oak during various below- and aboveground biotic interactions (2021)
    Berlin : Humboldt-Universität zu Berlin
    Details
    UID:
    edochu_18452_27922
    Format: 1 Online-Ressource (13 Seiten)
    Content: Endogenous rhythmic growth (ERG) is displayed by many tropical and some major temperate tree species and characterized by alternating root and shoot flushes (RF and SF). These flushes occur parallel to changes in biomass partitioning and in allocation of recently assimilated carbon and nitrogen. To address how biotic interactions interplay with ERG, we cross-compared the RF/SF shifts in oak microcuttings in the presence of pathogens, consumers and a mycorrhiza helper bacterium, without and with an ectomycorrhizal fungus (EMF), and present a synthesis of the observations. The typical increase in carbon allocation to sink leaves during SF did not occur in the presence of root or leaf pathogens, and the increase in nitrogen allocation to lateral roots during RF did not occur with the pathogens. The RF/SF shifts in resource allocation were mostly restored upon additional interaction with the EMF. Its presence led to increased resource allocation to principal roots during RF, also when the oaks were inoculated additionally with other interactors. The interactors affected the alternating, rhythmic growth and resource allocation shifts between shoots and roots. The restoring role of the EMF on RF/SF changes in parallel to the corresponding enhanced carbon and nitrogen allocation to sink tissues suggests that the EMF is supporting plants in maintaining the ERG.
    Content: Peer Reviewed
    In: London : Nature Publishing Group, 11,1
    Language: English
    DOI: 10.1038/s41598-021-03132-y
    DOI: 10.18452/27263
    URN: urn:nbn:de:kobv:11-110-18452/27922-6
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