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1.
PLoS One ; 19(10): e0309820, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-39453963

RESUMO

Biofilms in cooling towers represent a common habitat for the human pathogen Legionella pneumophila. Within the biofilm consortium, frequent interactions with protozoa, i.e. amoebae and ciliates, were reported, while nematodes have only recently been considered as potential environmental reservoir for the pathogenic bacteria. This study is the first approach to investigate the biotic interactions between L. pneumophila and bacterial-feeding nematodes in a semi-natural biofilm model. The species were Diploscapter coronatus, Diploscapter pachys, Plectus similis and Plectus sp., which all co-occur with L. pneumophila in the environment. Biofilms derived from cooling towers were either inoculated with mCherry-labeled L. pneumophila solely or in combination with GFP-labeled Escherichia coli. All experiments were conducted in single-species set-ups and multi-species (D. coronatus and P. similis) set-ups, to account for interspecific competition. Bacterial ingestion was assessed after 24 and 96 h as fluorescence patterns in the digestive tract of the nematodes using confocal laser scanning microscopy. L. pneumophila cells were ingested by all nematode species, with D. coronatus having the highest pathogen load. The fluorescence intensity (i.e. bacterial load) varied between compartments within the digestive tract and was independent of incubation time. Bacterial cells accumulated mostly around the cardia and in the intestine, while less cells were found within stoma and pharynx. Interspecific competition changed the pattern, i.e. with incubation of D. coronatus and P. similis in the same biofilm a significantly higher pathogen load occurred in the intestine of D. coronatus than P. similis after 24 h and 96 h. Remarkably, when given a choice between L. pneumophila and E. coli, P. similis was the only nematode species containing both bacteria after incubation for 24 h. None of the other nematode species contained E. coli after 24 h and 96 h incubation, while L. pneumophila was present. This study thus provides the first evidence, that under environmental conditions L. pneumophila is a frequent diet of bacterial-feeding nematodes, highlighting their potential as pathogen vectors or even host in cooling tower habitats.


Assuntos
Biofilmes , Legionella pneumophila , Legionella pneumophila/fisiologia , Animais , Biofilmes/crescimento & desenvolvimento , Nematoides/microbiologia , Nematoides/fisiologia , Humanos , Escherichia coli/fisiologia
2.
Biochim Biophys Acta Mol Cell Biol Lipids ; 1869(8): 159541, 2024 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-39097082

RESUMO

It is becoming increasingly clear that not only unicellular, photoautotrophic eukaryotes, plants, and fungi, but also invertebrates are capable of synthesizing ω3 long-chain polyunsaturated fatty acids (LC-PUFA) de novo. However, the distribution of this anabolic capacity among different invertebrate groups and its implementation at the gene and protein level are often still unknown. This study investigated the PUFA pathways in common soil fauna, i.e. two nematode and two Collembola species. Of these, one species each (Panagrellus redivivus, Folsomia candida) was assumed to produce ω3 LC-PUFA de novo, while the others (Acrobeloides bodenheimeri, Isotoma caerulea) were supposed to be unable to do so. A highly labeled oleic acid (99 % 13C) was supplemented and the isotopic signal was used to trace its metabolic path. All species followed the main pathway of lipid biosynthesis. However, in A. bodenheimeri this terminated at arachidonic acid (ω6 PUFA), whereas the other three species continued the pathway to eicosapentaenoic acid (ω3 PUFA), including I. caerulea. For the nematode P. redivivus the identification and functional characterization of four new fatty acid desaturase (FAD) genes was performed. These genes encode the FAD activities Δ9, Δ6, and Δ5, respectively. Additionally, the Δ12 desaturase was analyzed, yet the observed activity of an ω3 FAD could not be attributed to a coding gene. In the Collembola F. candida, 11 potential first desaturases (Δ9) and 13 front-end desaturases (Δ6 or Δ5 FADs) have been found. Further sequence analysis indicates the presence of omega FADs, specifically Δ12, which are likely derived from Δ9 FADs.


Assuntos
Artrópodes , Ácidos Graxos Insaturados , Nematoides , Solo , Animais , Nematoides/metabolismo , Nematoides/genética , Ácidos Graxos Insaturados/metabolismo , Ácidos Graxos Insaturados/biossíntese , Artrópodes/metabolismo , Artrópodes/genética , Solo/química , Solo/parasitologia , Ácidos Graxos Dessaturases/metabolismo , Ácidos Graxos Dessaturases/genética
3.
Artigo em Inglês | MEDLINE | ID: mdl-38040326

RESUMO

Many invertebrate species possess the metabolic ability to synthesize long-chain ω3 polyunsaturated fatty acids (PUFA) de novo. Due to their diverse effects on membrane architecture, neuroplasticity, growth and reproduction, PUFA have a high potential to positively influence the fitness of an organism. But how and when do these supposed advantages actually come into play? Other species, that are often closely related, pass natural selection without this special metabolic ability. The ω3-PUFA rich model organism Caenorhabditis elegans (Nematoda) and its mutant fat-1(wa9), lacking these PUFA, are a suitable test system. We analyzed potential impairments in reproduction and growth in a soil assay. Further, chemotaxis after aversive olfactory, associative learning and integration of a second sensory signal were assessed on agar plates. Moreover, we analyzed the phospholipid pattern of both C. elegans strains and further free-living nematodes species at different temperatures. While the phenotypic effects were rather small under standard conditions, lowering the temperature to 15 or even 10 °C or reducing the soil moisture, led to significant limitations, with the investigated parameters for neuroplasticity being most impaired. The ω3-PUFA free C. elegans mutant strain fat-1 did not adapt the fatty acid composition of its phospholipids to a decreasing temperature, while ω3-PUFA containing nematodes proportionally increased this PUFA group. In contrats, other ω3-PUFA free nematode species produced significantly more ω6-PUFA. Thus, the ability to synthesize long-chain ω3-PUFA de novo likely is fundamental for an increase in neuroplasticity and an efficient way for regulating membrane fluidity to maintain their functionality.


Assuntos
Ácidos Graxos Ômega-3 , Nematoides , Animais , Caenorhabditis elegans/genética , Caenorhabditis elegans/metabolismo , Ácidos Graxos Ômega-3/metabolismo , Ácidos Graxos Insaturados , Nematoides/metabolismo , Ácidos Graxos/metabolismo , Fosfolipídeos , Cognição , Solo
4.
Microorganisms ; 11(3)2023 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-36985310

RESUMO

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.

5.
Artigo em Inglês | MEDLINE | ID: mdl-36914111

RESUMO

17,18-Epoxyeicosatetraenoic acid (17,18-EEQ), the most abundant eicosanoid generated by cytochrome P450 (CYP) enzymes in C. elegans, is a potential signaling molecule in the regulation of pharyngeal pumping activity of this nematode. As a chiral molecule, 17,18-EEQ can exist in two stereoisomers, the 17(R),18(S)- and 17(S),18(R)-EEQ enantiomers. Here we tested the hypothesis that 17,18-EEQ may function as a second messenger of the feeding-promoting neurotransmitter serotonin and stimulates pharyngeal pumping and food uptake in a stereospecific manner. Serotonin treatment of wildtype worms induced a more than twofold increase of free 17,18-EEQ levels. As revealed by chiral lipidomics analysis, this increase was almost exclusively due to an enhanced release of the (R,S)-enantiomer of 17,18-EEQ. In contrast to the wildtype strain, serotonin failed to induce 17,18-EEQ formation as well as to accelerate pharyngeal pumping in mutant strains defective in the serotonin SER-7 receptor. However, the pharyngeal activity of the ser-7 mutant remained fully responsive to exogenous 17,18-EEQ administration. Short term incubations of well-fed and starved wildtype nematodes showed that both racemic 17,18-EEQ and 17(R),18(S)-EEQ were able to increase pharyngeal pumping frequency and the uptake of fluorescence-labeled microspheres, while 17(S),18(R)-EEQ and also 17,18-dihydroxyeicosatetraenoic acid (17,18-DHEQ, the hydrolysis product of 17,18-EEQ) were ineffective. Taken together, these results show that serotonin induces 17,18-EEQ formation in C. elegans via the SER-7 receptor and that both the formation of this epoxyeicosanoid and its subsequent stimulatory effect on pharyngeal activity proceed with high stereospecificity confined to the (R,S)-enantiomer.


Assuntos
Proteínas de Caenorhabditis elegans , Caenorhabditis elegans , Animais , Caenorhabditis elegans/fisiologia , Serotonina/farmacologia , Proteínas de Caenorhabditis elegans/genética , Eicosanoides , Sistema Enzimático do Citocromo P-450
6.
Sci Rep ; 11(1): 23680, 2021 12 08.
Artigo em Inglês | MEDLINE | ID: mdl-34880358

RESUMO

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.


Assuntos
Interações entre Hospedeiro e Microrganismos , Micorrizas/fisiologia , Quercus/microbiologia , Quercus/fisiologia , Simbiose , Biomassa , Especificidade de Órgãos , Desenvolvimento Vegetal , Fenômenos Fisiológicos Vegetais
7.
Ecol Evol ; 11(16): 11065-11076, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34429903

RESUMO

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.

8.
Philos Trans R Soc Lond B Biol Sci ; 375(1804): 20190650, 2020 08 03.
Artigo em Inglês | MEDLINE | ID: mdl-32536311

RESUMO

Quantitative fatty acid signature analysis (QFASA) is widely used to investigate trophic interactions in marine ecosystems, as nutritionally important ω3 long-chain polyunsaturated fatty acids at the food web base allow tracing of their trophic transfer in the food chain. By contrast, the basal resources in soil food webs comprise a wider array of trophic markers, including branched-chain, cyclopropane as well as several mono- and polyunsaturated fatty acids. These diverse markers allow distinguishing between the three dominant soil carbon and energy channels, the root, bacterial and fungal pathway. QFASA has not been applied yet to soil ecosystems owing to the lack of a priori data to fit the model. The present work investigates the transfer of absolute and relative trophic marker fatty acids into Collembola as dominant representatives of the soil mesofauna. Three different species were fed on a variety of single diets characteristic for the green and brown food chain. Calibration coefficients were calculated and diet estimation trials for mixed diet set-ups were performed, using a library comprising 50 different resources. However, estimation of Collembola diet was only partially successful, identifying the main components, but not the correct relative proportions. Adjustments by fat content or diet group exclusion did not improve the results. Nonetheless, this work provides, to our knowledge, a first comprehensive dataset to translate the application of QFASA from marine to soil ecosystems. This article is part of the theme issue 'The next horizons for lipids as 'trophic biomarkers': evidence and significance of consumer modification of dietary fatty acids'.


Assuntos
Artrópodes/química , Biomarcadores/análise , Ácidos Graxos/análise , Cadeia Alimentar , Solo , Animais , Dieta , Especificidade da Espécie
9.
Philos Trans R Soc Lond B Biol Sci ; 375(1804): 20190641, 2020 08 03.
Artigo em Inglês | MEDLINE | ID: mdl-32536315

RESUMO

To understand consumer dietary requirements and resource use across ecosystems, researchers have employed a variety of methods, including bulk stable isotope and fatty acid composition analyses. Compound-specific stable isotope analysis (CSIA) of fatty acids combines both of these tools into an even more powerful method with the capacity to broaden our understanding of food web ecology and nutritional dynamics. Here, we provide an overview of the potential that CSIA studies hold and their constraints. We first review the use of fatty acid CSIA in ecology at the natural abundance level as well as enriched physiological tracers, and highlight the unique insights that CSIA of fatty acids can provide. Next, we evaluate methodological best practices when generating and interpreting CSIA data. We then introduce three cutting-edge methods: hydrogen CSIA of fatty acids, and fatty acid isotopomer and isotopologue analyses, which are not yet widely used in ecological studies, but hold the potential to address some of the limitations of current techniques. Finally, we address future priorities in the field of CSIA including: generating more data across a wider range of taxa; lowering costs and increasing laboratory availability; working across disciplinary and methodological boundaries; and combining approaches to answer macroevolutionary questions. This article is part of the theme issue 'The next horizons for lipids as 'trophic biomarkers': evidence and significance of consumer modification of dietary fatty acids'.


Assuntos
Isótopos de Carbono/análise , Deutério/análise , Ecologia/métodos , Ácidos Graxos/análise , Cadeia Alimentar , Isótopos de Nitrogênio/análise
10.
Sci Total Environ ; 704: 135418, 2020 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-31896218

RESUMO

Ecological communities in forests have been shown to be strongly affected by forest management but a detailed understanding of how different components of management affect insect communities directly and indirectly via environmental variables, how management influences functional trait diversity and composition, and whether these results can be transferred to other functional groups besides insects (e.g. bacteria or nematodes) is still missing. To address these questions we used water-filled tree holes, which provide habitats for insect larvae and other aquatic organisms in forests, as a model system. We mapped all water-filled tree holes in 75 forest plots (1 ha) under different management intensity in three regions of Germany. We measured structural and climatic conditions at different spatial scales, sampled insect communities in 123 tree holes and bacterial and nematode communities in a subset of these. We found that forest management in terms of harvesting intensity and the proportion of non-natural tree species (species not part of the natural vegetation at the sites) negatively affected tree-hole abundance. An increased proportion of non-natural tree species had a positive direct effect on insect richness and functional diversity in the tree holes. However, a structural equation model showed that increasing management intensity had negative indirect effects on insect abundance and richness, operating via environmental variables at stand and tree-hole scale. Functional diversity and trait composition of insect communities similarly responded to changes in management-related variables. In contrast to insects, bacterial and nematode richness were not directly impacted by forest management but by other environmental variables. Our results suggest that forest management may strongly alter insect communities of tree holes, while nematodes and bacteria seem less affected. Most effects in our study were indirect and negative, indicating that management has often complex consequences for forest communities that should be taken into account in forest management schemes.


Assuntos
Organismos Aquáticos , Animais , Biodiversidade , Ecossistema , Alemanha , Insetos
11.
PLoS One ; 14(8): e0221102, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31430306

RESUMO

Soil food webs are important drivers for key ecological functions in terrestrial systems such as carbon and nutrient cycling. However, soil food web models generally lack quantitative data, mainly due to the shortage in high-throughput methods to describe energy flows. In marine environments, multivariate optimization models (Quantitative Fatty Acid Signature Analysis) and Bayesian approaches (source-tracking algorithm) were established to predict the proportion of predator diets using lipids as tracers. A premise for the application of such models to soil systems is to acquire the fatty acid pattern of a broad range of resources and to reveal potential overlap in their signatures. We present a comprehensive comparison of lipid pattern across widespread taxa of plants (leaves and roots, n = 48), algae (n = 59), fungi (n = 60), and bacteria (n = 62) as basal food web resources. Lipid profiles from microorganisms and algae were assessed from laboratory cultures, whereas plant tissue was derived from an arable field. A lipid library was constructed and multivariate data analyses (hierarchical clustering, nMDS) was used to assess the extent of separation in lipid pattern by species or resource type. The performance of the lipid library was tested by leave-one-prey-out (LOPO) analysis, giving the distinctiveness of the resource (prey) groups. Fungi and plant leaves were correctly assigned based on their lipid pattern with more than 98%, while plant roots and bacteria achieved 88 and 85%, respectively. However, algae were only correctly classified by 60%, pointing to a bias in the herbivore food chain. Fatty acids most important for separation of algae and plant leaves were of the omega 3 type, i.e. 16:3ω3 and 18:3ω3. In plant roots 18:1ω9 was most important, whereas bacteria were distinguished predominantly by methyl-branched fatty acids. Overall, the lipid pattern of major soil food web resources are sufficiently differentiated to allow for qualitative (biomarker) analyses as well as quantitative modelling, yet with precaution in the case of algae.


Assuntos
Ácidos Graxos/análise , Cadeia Alimentar , Modelos Biológicos , Solo/química , Animais , Bactérias/química , Bactérias/metabolismo , Ácidos Graxos/metabolismo , Fungos/química , Fungos/metabolismo , Folhas de Planta/química , Folhas de Planta/metabolismo , Raízes de Plantas/química , Raízes de Plantas/metabolismo , Plantas/química , Plantas/metabolismo , Microbiologia do Solo
12.
Biochim Biophys Acta Mol Cell Biol Lipids ; 1864(9): 1194-1205, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31108204

RESUMO

For vertebrates, the adequate supply of polyunsaturated fatty acids (PUFA) by the diet, in particular ω3 long-chain PUFA, is considered essential for neural development, growth and reproduction. In contrast to aquatic ecosystems, ω3 long-chain PUFA apparently are not widely available in the terrestrial food chain. Their de novo synthesis requires the presence of Δ12 and ω3 fatty acid desaturase enzymes, which are absent in vertebrates but present, for example, in the nematode Caenorhabditis elegans (FAT-2 and FAT-1). This raises the question if soil-dwelling nematodes offer substantial supply of these valuable nutritional compounds in terrestrial food webs. BLAST searches in available nematode genomes revealed the existence of fat-2 like genes in almost all clade III-V species, but failed to identify orthologs in clade I-II nematodes. An additional RT-PCR screen across soil-dwelling nematode species identified six novel fat-2 like genes. Hints for the genetic basis of a ω3 (fat-1) desaturase activity was found only in selected clade IV-V species, but not in clades I to III nematodes. Fatty acid pattern analyses following a PUFA-free cultivation and enzymatic characterization of six selected fat-2 or fat-1 like desaturases in yeast confirmed the findings from the genetic approaches. Thus, in similar soil habitats, taxa exist that can synthesize ω3 long-chain PUFA (as Panagrolaimus, Mesorhabditis and Caenorhabditis) whereas others are unable to do so (Acrobeloides, Cephalobus and Oscheius). While these nematodes do not differ in trophic position or major diet, distinction in reproduction mode may have led to the observed variations in desaturase genes.


Assuntos
Ácidos Graxos Dessaturases/metabolismo , Proteínas de Helminto/metabolismo , Nematoides/metabolismo , Sequência de Aminoácidos , Animais , Evolução Molecular , Ácidos Graxos Dessaturases/química , Ácidos Graxos Dessaturases/genética , Ácidos Graxos Insaturados/metabolismo , Proteínas de Helminto/química , Proteínas de Helminto/genética , Nematoides/química , Nematoides/genética , Filogenia , Conformação Proteica , Alinhamento de Sequência , Estereoisomerismo
13.
Ecotoxicol Environ Saf ; 174: 506-513, 2019 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-30861438

RESUMO

The herbicide Roundup (and glyphosate, its active ingredient) is extensively used for weed control on a worldwide scale. It is absorbed after foliar application and quickly translocated inside the plant. In this study, we investigated the effects of Roundup speed, a commercial glyphosate formulation, on the structural composition (dominance of microbial groups, phospholipid fatty acid analysis - PLFA) and functional diversity (use of carbon sources, Multiple Substrate Induced Respiration - MSIR) of soil microorganisms. We specifically aimed at understanding the potential impact of biotic interactions on herbicide effects and included plants, earthworms, and endomycorrhizal fungi in the experimental setup. For this, we grew clover (Trifolium repens) in the greenhouse and added mycorrhizal inoculum (Glomus mosseae) and earthworms (Lumbricus terrestris) to the pots. Two weeks after foliar Roundup application and subsequent plant death, the pots were destructively sampled. The application resulted in a significant increase of microbial respiration (SIR) by approximately 30%. A multivariate analysis of the MSIR data exhibited small but significant differences between the microbial communities of treated and untreated pots, while no significant difference was apparent for the PLFA data. Bacterial PLFAs generally decreased following herbicide application, while mycorrhizal and fungal PLFAs were not affected. We did not find a consistent difference between the fatty acid markers of gram negative and gram positive bacteria. For all investigated parameters, there were highly significant differences between the upper (0-5 cm depth) and lower (5-10 cm) soil layers. The fact that rooting density differed by a factor of 3.5 between the two layers indicated that herbicide effects were especially pronounced in the clover rhizosphere and were likely due to changes in root exudate composition. We found significant, though very small, interactions between Roundup and other experimental factors (especially mycorrhizal inoculum).


Assuntos
Glicina/análogos & derivados , Herbicidas/toxicidade , Microbiota/efeitos dos fármacos , Microbiologia do Solo/normas , Solo/química , Animais , Glomeromycota/efeitos dos fármacos , Glomeromycota/crescimento & desenvolvimento , Glicina/análise , Glicina/toxicidade , Herbicidas/análise , Medicago/efeitos dos fármacos , Medicago/crescimento & desenvolvimento , Micorrizas/efeitos dos fármacos , Oligoquetos/efeitos dos fármacos , Oligoquetos/crescimento & desenvolvimento , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/crescimento & desenvolvimento , Rizosfera , Glifosato
14.
Ecol Lett ; 22(1): 170-180, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30463104

RESUMO

While forest management strongly influences biodiversity, it remains unclear how the structural and compositional changes caused by management affect different community dimensions (e.g. richness, specialisation, abundance or completeness) and how this differs between taxa. We assessed the effects of nine forest features (representing stand structure, heterogeneity and tree composition) on thirteen above- and belowground trophic groups of plants, animals, fungi and bacteria in 150 temperate forest plots differing in their management type. Canopy cover decreased light resources, which increased community specialisation but reduced overall diversity and abundance. Features increasing resource types and diversifying microhabitats (admixing of oaks and conifers) were important and mostly affected richness. Belowground groups responded differently to those aboveground and had weaker responses to most forest features. Our results show that we need to consider forest features rather than broad management types and highlight the importance of considering several groups and community dimensions to better inform conservation.


Assuntos
Biodiversidade , Árvores , Animais , Fungos
15.
Toxins (Basel) ; 10(7)2018 07 09.
Artigo em Inglês | MEDLINE | ID: mdl-29987228

RESUMO

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.


Assuntos
Citrinina/toxicidade , Zearalenona/análogos & derivados , Zearalenona/toxicidade , Animais , Caenorhabditis elegans/efeitos dos fármacos , Caenorhabditis elegans/metabolismo
16.
J Vis Exp ; (134)2018 04 17.
Artigo em Inglês | MEDLINE | ID: mdl-29733305

RESUMO

Fatty acids (FAs) are useful biomarkers in food web ecology because they are typically assimilated as a complete molecule and transferred into consumer tissue with minor or no modification, allowing the dietary routing between different trophic levels. However, the FA trophic marker approach is still hampered by the limited knowledge in lipid metabolism of the soil fauna. This study used entirely labelled palmitic acid (13C16:0, 99 atom%) as a tracer in fatty acid metabolism pathways of two widespread soil Collembola, Protaphorura fimata and Heteromurus nitidus. In order to investigate the fate and metabolic modifications of this precursor, a method of isotopologue profiling is presented, performed by mass spectrometry using single ion monitoring. Moreover, the upstream laboratory feeding experiment is described, as well as the extraction and methylation of dominant lipid fractions (neutral lipids, phospholipids) and the related formula and calculations. Isotopologue profiling does not only yield the overall 13C enrichment in fatty acids derived from the 13C labeled precursor but also produces the pattern of isotopologues exceeding the mass of the parent ion (i.e., the FA molecular ion M+) of each labeled FA by one or more mass units (M+1, M+2, M+3, etc.). This knowledge allows conclusions on the ratio of dietary routing of an entirely consumed FA in comparison to de novo biosynthesis. The isotopologue profiling is suggested as a useful tool for evaluation of fatty acid metabolism in soil animals to disentangle trophic interactions.


Assuntos
Isótopos de Carbono/metabolismo , Ácidos Graxos/metabolismo , Invertebrados/metabolismo , Animais , Ácidos Graxos/análise , Metabolismo dos Lipídeos , Ácido Palmítico/química , Ácido Palmítico/metabolismo
17.
Pedobiologia (Jena) ; 63: 1-7, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29129942

RESUMO

The ecological interactions that occur in and with soil are of consequence in many ecosystems on the planet. These interactions provide numerous essential ecosystem services, and the sustainable management of soils has attracted increasing scientific and public attention. Although soil ecology emerged as an independent field of research many decades ago, and we have gained important insights into the functioning of soils, there still are fundamental aspects that need to be better understood to ensure that the ecosystem services that soils provide are not lost and that soils can be used in a sustainable way. In this perspectives paper, we highlight some of the major knowledge gaps that should be prioritized in soil ecological research. These research priorities were compiled based on an online survey of 32 editors of Pedobiologia - Journal of Soil Ecology. These editors work at universities and research centers in Europe, North America, Asia, and Australia.The questions were categorized into four themes: (1) soil biodiversity and biogeography, (2) interactions and the functioning of ecosystems, (3) global change and soil management, and (4) new directions. The respondents identified priorities that may be achievable in the near future, as well as several that are currently achievable but remain open. While some of the identified barriers to progress were technological in nature, many respondents cited a need for substantial leadership and goodwill among members of the soil ecology research community, including the need for multi-institutional partnerships, and had substantial concerns regarding the loss of taxonomic expertise.

18.
PLoS One ; 12(7): e0180264, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28704438

RESUMO

Soil food web structure and function is primarily determined by the major basal resources, which are living plant tissue, root exudates and dead organic matter. A field experiment was performed to disentangle the interlinkage of the root-and detritus-based soil food chains. An arable site was cropped either with maize, amended with maize shoot litter or remained bare soil, representing food webs depending on roots, aboveground litter and soil organic matter as predominant resource, respectively. The soil micro-food web, i.e. microorganisms and nematodes, was investigated in two successive years along a depth transect. The community composition of nematodes was used as model to determine the changes in the rhizosphere, detritusphere and bulk soil food web. In the first growing season the impact of treatments on the soil micro-food web was minor. In the second year plant-feeding nematodes increased under maize, whereas after harvest the Channel Index assigned promotion of the detritivore food chain, reflecting decomposition of root residues. The amendment with litter did not foster microorganisms, instead biomass of Gram-positive and Gram-negative bacteria as well as that of fungi declined in the rooted zone. Likely higher grazing pressure by nematodes reduced microbial standing crop as bacterial and fungal feeders increased. However, populations at higher trophic levels were not promoted, indicating limited flux of litter resources along the food chain. After two years of bare soil microbial biomass and nematode density remained stable, pointing to soil organic matter-based resources that allow bridging periods with deprivation. Nematode communities were dominated by opportunistic taxa that are competitive at moderate resource supply. In sum, removal of plants from the system had less severe effects than expected, suggesting considerable food web resilience to the disruption of both the root and detrital carbon channel, pointing to a legacy of organic matter resources in arable soils.


Assuntos
Bactérias/crescimento & desenvolvimento , Fungos/crescimento & desenvolvimento , Nematoides/crescimento & desenvolvimento , Solo/química , Animais , Bactérias/classificação , Ecossistema , Comportamento Alimentar , Cadeia Alimentar , Fungos/classificação , Nematoides/classificação , Rizosfera , Microbiologia do Solo
19.
BMC Genomics ; 17(1): 627, 2016 08 12.
Artigo em Inglês | MEDLINE | ID: mdl-27520023

RESUMO

BACKGROUND: Pedunculate oak (Quercus robur L.), an important forest tree in temperate ecosystems, displays an endogenous rhythmic growth pattern, characterized by alternating shoot and root growth flushes paralleled by oscillations in carbon allocation to below- and aboveground tissues. However, these common plant traits so far have largely been neglected as a determining factor for the outcome of plant biotic interactions. This study investigates the response of oak to migratory root-parasitic nematodes in relation to rhythmic growth, and how this plant-nematode interaction is modulated by an ectomycorrhizal symbiont. Oaks roots were inoculated with the nematode Pratylenchus penetrans solely and in combination with the fungus Piloderma croceum, and the systemic impact on oak plants was assessed by RNA transcriptomic profiles in leaves. RESULTS: The response of oaks to the plant-parasitic nematode was strongest during shoot flush, with a 16-fold increase in the number of differentially expressed genes as compared to root flush. Multi-layered defence mechanisms were induced at shoot flush, comprising upregulation of reactive oxygen species formation, hormone signalling (e.g. jasmonic acid synthesis), and proteins involved in the shikimate pathway. In contrast during root flush production of glycerolipids involved in signalling cascades was repressed, suggesting that P. penetrans actively suppressed host defence. With the presence of the mycorrhizal symbiont, the gene expression pattern was vice versa with a distinctly stronger effect of P. penetrans at root flush, including attenuated defence, cell and carbon metabolism, likely a response to the enhanced carbon sink strength in roots induced by the presence of both, nematode and fungus. Meanwhile at shoot flush, when nutrients are retained in aboveground tissue, oak defence reactions, such as altered photosynthesis and sugar pathways, diminished. CONCLUSIONS: The results highlight that gene response patterns of plants to biotic interactions, both negative (i.e. plant-parasitic nematodes) and beneficial (i.e. mycorrhiza), are largely modulated by endogenous rhythmic growth, and that such plant traits should be considered as an important driver of these relationships in future studies.


Assuntos
Interações Hospedeiro-Parasita/genética , Quercus/genética , Quercus/parasitologia , Tylenchoidea/fisiologia , Animais , Regulação para Baixo , Perfilação da Expressão Gênica , Folhas de Planta/genética , Folhas de Planta/metabolismo , Folhas de Planta/parasitologia , Raízes de Plantas/genética , Raízes de Plantas/metabolismo , Raízes de Plantas/parasitologia , Brotos de Planta/genética , Brotos de Planta/metabolismo , Brotos de Planta/parasitologia , Quercus/crescimento & desenvolvimento , RNA de Plantas/isolamento & purificação , RNA de Plantas/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Transcriptoma , Regulação para Cima
20.
Microb Ecol ; 70(2): 390-9, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-25687125

RESUMO

Soil fungi play an essential role in the decomposition of plant-derived organic material entering soils. The quality and quantity of organic compounds vary seasonally as well as with soil depth. To elucidate how these resources affect fungal communities in an arable soil, a field experiment was set up with two plant species, maize and wheat. Resource availability was experimentally manipulated by maize litter input on one half of these maize and wheat plots after harvest in autumn. Fungal biomass was determined by ergosterol quantification, and community structure was investigated by fungal automated ribosomal intergenic spacer analysis (F-ARISA). An annual cycle was assessed across a depth gradient, distinguishing three soil habitats: the plough layer, rooted soil below the plough layer, and deeper root-free soil. Fungal communities appeared highly dynamic and varied according to soil depth and plant resources. In the plough layer, the availability of litter played a dominant role in shaping fungal communities, whereas in the rooted layer below, community structure and biomass mainly differed between plant species. This plant effect was also extended into the root-free soil at a depth of 70 cm. In winter, the availability of litter also affected fungal communities in deeper soil layers, suggesting vertical transport processes under fallow conditions. These distinct resource effects indicate diverse ecological niches along the soil profile, comprising specific fungal metacommunities. The recorded responses to both living plants and litter point to a central role of fungi in connecting primary production and decomposition within the plant-soil system.


Assuntos
Fungos/fisiologia , Microbiologia do Solo , Biomassa , Ecossistema , Fungos/isolamento & purificação , Fungos/metabolismo
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