Soil Contamination due to Arsenic-Enriched Irrigation Water - Impact of Irrigation Practices

Increasing irrigation with arsenic (As) contaminated groundwater represents a growing problem in the densely populated delta and floodplain regions of SE Asia. The overarching aim of this study was to evaluate retention and mobility of As in soils in dependence of the irrigation practice. Irrigation of calcareous agricultural soils was simulated in a green-house experiment, in which artificial anoxic groundwater enriched in dissolved AsIII (10 mg/L) was applied regularly. We compared the following three different irrigation scenarios: permanently flooded, promoting reducing conditions (R); alternating flood irrigation, characterized by frequent changes in water saturation (RO); and sprinkler irrigation, maintaining permanently oxic conditions (O). Several wet chemical extraction procedures were carried out to characterize soil As storage pools at the end of the experiment. Pore water analysis reflected strongly reducing redox conditions (up to 42.9 mg/L dissolved Fe) for the R treatment, while less reducing conditions developed in the RO scenario (Fe max. 0.14 mg/L). Furthermore, As concentrations in pore water increased steadily to 1.34 (R) and 0.39 mg/L (O), respectively, with 20% (R) and 80% (RO) being present in the oxidized form AsV. The addition of As by irrigation water resulted in surprisingly similar depth distributions being independent of the irrigation treatment. Highest As contents (R: 52.2, RO: 49.6 and O: 43.9 mg/kg) occurred within the top 0-2 cm and decreased rapidly to values close the initial content (11.5 mg/kg) below 4 cm depth. This reflects a generally high sorption capacity of the soil for As. Even reductive dissolution of Fe-phases and the accompanying loss of sorption sites (R treatment) did not affect the As sorption behavior in general. However, pore water As concentrations and sequential extraction results point at a higher As mobility in case of the R treatment. This can be explained by the higher proportion of AsIII in the pore water, which is more mobile than AsV at the prevailing conditions. In sum, the three irrigation practices did not result in differences regarding the vertical distribution of As, but permanent flooding clearly increased the mobility of As as compared to the other treatments. The comparison of different wet chemical extraction procedures further emphasizes that protocol and sample treatment should be selected with caution, especially when redox conditions in the soil vary

Expression of Interleukin-1 and Interleukin-1 Receptors Type 1 and Type 2 in Hodgkin Lymphoma

Signaling through the IL-1-receptor type 1 (IL-1R1), IL-1 is required for initiation and maintenance of diverse activities of the immune system. A second receptor, IL-1R2, blocks IL-1 signal transduction. We studied expression of IL-1beta, IL-1R1, and IL-1R2 in 17 Hodgkin lymphomas (HL) by in situ hybridization (ISH). IL-1beta expressing cells, morphologically consistent with endothelial cells and fibroblasts, occurred in all HL tissues with elevated transcript levels in areas of active fibrosis. Hodgkin and Reed-Sternberg (HRS) cells of all cases expressed low IL-1R1 transcript levels in some tumor cells, and high levels of IL-1R2 in large proportions of HRS cells. Only few bystander cells showed low levels of IL-1R1 and IL-1R2 RNA. Supernatants of 4 out of 7 HL-derived cell lines contained soluble IL-1R2 protein at high levels. HL patient sera carried variably amounts of IL-1R2 protein with significantly increased titers in patients with active disease compared to patients in complete remission and control individuals without HL. Western blots and co-immunoprecipitations showed binding of the IL-1R2 to the intracellular IL-1R-accessory protein (IL-1IRAcP). These data suggest functions of the IL-1R2 as a „decoy-receptor” sequestrating paracrine IL-1 extracellularly and intracellularly by engaging IL-1IRAcP, thus depriving IL1-R1 molecules of their extracellular and intracellular ligands. Expression of IL1-R2 by HRS cells seems to contribute to local and systemic modulation of immune function in HL

Temporal and small-scale spatial variation in grassland productivity, biomass quality, and nutrient limitation

Characterization of spatial and temporal variation in grassland productivity and nutrition is crucial for a comprehensive understanding of ecosystem function. Although within-site heterogeneity in soil and plant properties has been shown to be relevant for plant community stability, spatiotemporal variability in these factors is still understudied in temperate grasslands. Our study aimed to detect if soil characteristics and plant diversity could explain observed small-scale spatial and temporal variability in grassland productivity, biomass nutrient concentrations, and nutrient limitation. Therefore, we sampled 360 plots of 20 cm × 20 cm each at six consecutive dates in an unfertilized grassland in Southern Germany. Nutrient limitation was estimated using nutrient ratios in plant biomass. Absolute values of, and spatial variability in, productivity, biomass nutrient concentrations, and nutrient limitation were strongly associated with sampling date. In April, spatial heterogeneity was high and most plots showed phosphorous deficiency, while later in the season nitrogen was the major limiting nutrient. Additionally, a small significant positive association between plant diversity and biomass phosphorus concentrations was observed, but should be tested in more detail. We discuss how low biological activity e.g., of soil microbial organisms might have influenced observed heterogeneity of plant nutrition in early spring in combination with reduced active acquisition of soil resources by plants. These early-season conditions are particularly relevant for future studies as they differ substantially from more thoroughly studied later season conditions. Our study underlines the importance of considering small spatial scales and temporal variability to better elucidate mechanisms of ecosystem functioning and plant community assembly

Direct and plant community mediated effects of management intensity on annual nutrient leaching risk in temperate grasslands

Grassland management intensity influences nutrient cycling both directly, by changing nutrient inputs and outputs from the ecosystem, and indirectly, by altering the nutrient content, and the diversity and functional composition of plant and microbial communities. However, the relative importance of these direct and indirect processes for the leaching of multiple nutrients is poorly studied. We measured the annual leaching of nitrate, ammonium, phosphate and sulphate at a depth of 10 cm in 150 temperate managed grasslands using a resin method. Using Structural Equation Modeling, we distinguished between various direct and indirect effects of management intensity (i.e. grazing and fertilization) on nutrient leaching. We found that management intensity was positively associated with nitrate, ammonium and phosphate leaching risk both directly (i.e. via increased nutrient inputs) and indirectly, by changing the stoichiometry of soils, plants and microbes. In contrast, sulphate leaching risk was negatively associated with management intensity, presumably due to increased outputs with mowing and grazing. In addition, management intensification shifted plant communities towards an exploitative functional composition (characterized by high tissue turnover rates) and, thus, further promoted the leaching risk of inorganic nitrogen. Plant species richness was associated with lower inorganic nitrogen leaching risk, but most of its effects were mediated by stoichiometry and plant community functional traits. Maintaining and restoring diverse plant communities may therefore mitigate the increased leaching risk that management intensity imposes upon grasslands

Biodiversity effects on ecosystem functioning in a 15-year grassland experiment: Patterns, mechanisms, and open questions

In the past two decades, a large number of studies have investigated the relationship between biodiversity and ecosystem functioning, most of which focussed on a limited set of ecosystem variables. The Jena Experiment was set up in 2002 to investigate the effects of plant diversity on element cycling and trophic interactions, using a multi-disciplinary approach. Here, we review the results of 15 years of research in the Jena Experiment, focussing on the effects of manipulating plant species richness and plant functional richness. With more than 85,000 measures taken from the plant diversity plots, the Jena Experiment has allowed answering fundamental questions important for functional biodiversity research. First, the question was how general the effect of plant species richness is, regarding the many different processes that take place in an ecosystem. About 45% of different types of ecosystem processes measured in the ‘main experiment’, where plant species richness ranged from 1 to 60 species, were significantly affected by plant species richness, providing strong support for the view that biodiversity is a significant driver of ecosystem functioning. Many measures were not saturating at the 60-species level, but increased linearly with the logarithm of species richness. There was, however, great variability in the strength of response among different processes. One striking pattern was that many processes, in particular belowground processes, took several years to respond to the manipulation of plant species richness, showing that biodiversity experiments have to be long-term, to distinguish trends from transitory patterns. In addition, the results from the Jena Experiment provide further evidence that diversity begets stability, for example stability against invasion of plant species, but unexpectedly some results also suggested the opposite, e.g. when plant communities experience severe perturbations or elevated resource availability. This highlights the need to revisit diversity–stability theory. Second, we explored whether individual plant species or individual plant functional groups, or biodiversity itself is more important for ecosystem functioning, in particular biomass production. We found strong effects of individual species and plant functional groups on biomass production, yet these effects mostly occurred in addition to, but not instead of, effects of plant species richness. Third, the Jena Experiment assessed the effect of diversity on multitrophic interactions. The diversity of most organisms responded positively to increases in plant species richness, and the effect was stronger for above- than for belowground organisms, and stronger for herbivores than for carnivores or detritivores. Thus, diversity begets diversity. In addition, the effect on organismic diversity was stronger than the effect on species abundances. Fourth, the Jena Experiment aimed to assess the effect of diversity on N, P and C cycling and the water balance of the plots, separating between element input into the ecosystem, element turnover, element stocks, and output from the ecosystem. While inputs were generally less affected by plant species richness, measures of element stocks, turnover and output were often positively affected by plant diversity, e.g. carbon storage strongly increased with increasing plant species richness. Variables of the N cycle responded less strongly to plant species richness than variables of the C cycle. Fifth, plant traits are often used to unravel mechanisms underlying the biodiversity–ecosystem functioning relationship. In the Jena Experiment, most investigated plant traits, both above- and belowground, were plastic and trait expression depended on plant diversity in a complex way, suggesting limitation to using database traits for linking plant traits to particular functions. Sixth, plant diversity effects on ecosystem processes are often caused by plant diversity effects on species interactions. Analyses in the Jena Experiment including structural equation modelling suggest complex interactions that changed with diversity, e.g. soil carbon storage and greenhouse gas emission were affected by changes in the composition and activity of the belowground microbial community. Manipulation experiments, in which particular organisms, e.g. belowground invertebrates, were excluded from plots in split-plot experiments, supported the important role of the biotic component for element and water fluxes. Seventh, the Jena Experiment aimed to put the results into the context of agricultural practices in managed grasslands. The effect of increasing plant species richness from 1 to 16 species on plant biomass was, in absolute terms, as strong as the effect of a more intensive grassland management, using fertiliser and increasing mowing frequency. Potential bioenergy production from high-diversity plots was similar to that of conventionally used energy crops. These results suggest that diverse ‘High Nature Value Grasslands’ are multifunctional and can deliver a range of ecosystem services including production-related services. A final task was to assess the importance of potential artefacts in biodiversity–ecosystem functioning relationships, caused by the weeding of the plant community to maintain plant species composition. While the effort (in hours) needed to weed a plot was often negatively related to plant species richness, species richness still affected the majority of ecosystem variables. Weeding also did not negatively affect monoculture performance; rather, monocultures deteriorated over time for a number of biological reasons, as shown in plant-soil feedback experiments. To summarize, the Jena Experiment has allowed for a comprehensive analysis of the functional role of biodiversity in an ecosystem. A main challenge for future biodiversity research is to increase our mechanistic understanding of why the magnitude of biodiversity effects differs among processes and contexts. It is likely that there will be no simple answer. For example, among the multitude of mechanisms suggested to underlie the positive plant species richness effect on biomass, some have received limited support in the Jena Experiment, such as vertical root niche partitioning. However, others could not be rejected in targeted analyses. Thus, from the current results in the Jena Experiment, it seems likely that the positive biodiversity effect results from several mechanisms acting simultaneously in more diverse communities, such as reduced pathogen attack, the presence of more plant growth promoting organisms, less seed limitation, and increased trait differences leading to complementarity in resource uptake. Distinguishing between different mechanisms requires careful testing of competing hypotheses. Biodiversity research has matured such that predictive approaches testing particular mechanisms are now possible

The Evolution of Ecological Diversity in Acidobacteria

Acidobacteria occur in a large variety of ecosystems worldwide and are particularly abundant and highly diverse in soils. In spite of their diversity, only few species have been characterized to date which makes Acidobacteria one of the most poorly understood phyla among the domain Bacteria. We used a culture-independent niche modeling approach to elucidate ecological adaptations and their evolution for 4,154 operational taxonomic units (OTUs) of Acidobacteria across 150 different, comprehensively characterized grassland soils in Germany. Using the relative abundances of their 16S rRNA gene transcripts, the responses of active OTUs along gradients of 41 environmental variables were modeled using hierarchical logistic regression (HOF), which allowed to determine values for optimum activity for each variable (niche optima). By linking 16S rRNA transcripts to the phylogeny of full 16S rRNA gene sequences, we could trace the evolution of the different ecological adaptations during the diversification of Acidobacteria. This approach revealed a pronounced ecological diversification even among acidobacterial sister clades. Although the evolution of habitat adaptation was mainly cladogenic, it was disrupted by recurrent events of convergent evolution that resulted in frequent habitat switching within individual clades. Our findings indicate that the high diversity of soil acidobacterial communities is largely sustained by differential habitat adaptation even at the level of closely related species. A comparison of niche optima of individual OTUs with the phenotypic properties of their cultivated representatives showed that our niche modeling approach (1) correctly predicts those physiological properties that have been determined for cultivated species of Acidobacteria but (2) also provides ample information on ecological adaptations that cannot be inferred from standard taxonomic descriptions of bacterial isolates. These novel information on specific adaptations of not-yet-cultivated Acidobacteria can therefore guide future cultivation trials and likely will increase their cultivation success

Above- and belowground biodiversity jointly tighten the P cycle in agricultural grasslands

Experiments showed that biodiversity increases grassland productivity and nutrient exploitation, potentially reducing fertiliser needs. Enhancing biodiversity could improve P-use efficiency of grasslands, which is beneficial given that rock-derived P fertilisers are expected to become scarce in the future. Here, we show in a biodiversity experiment that more diverse plant communities were able to exploit P resources more completely than less diverse ones. In the agricultural grasslands that we studied, management effects either overruled or modified the driving role of plant diversity observed in the biodiversity experiment. Nevertheless, we show that greater above- (plants) and belowground (mycorrhizal fungi) biodiversity contributed to tightening the P cycle in agricultural grasslands, as reduced management intensity and the associated increased biodiversity fostered the exploitation of P resources. Our results demonstrate that promoting a high above- and belowground biodiversity has ecological (biodiversity protection) and economical (fertiliser savings) benefits. Such win-win situations for farmers and biodiversity are crucial to convince farmers of the benefits of biodiversity and thus counteract global biodiversity loss

Veränderungen der mikrobiellen Gemeinschaft in Grünlandböden als Reaktion auf kurz- und langfristiges Flächenmanagement

Im Rahmen des DFG Schwerpunktprogramms Biodiversitäts-Exploratorien (www.biodiversity-exploratories.de) wurden in 150 Grünlandböden die Veränderungen der mikrobiellen Gemeinschaftsstruktur und Enzymaktivität über einen Zeitraum von drei Jahren untersucht. Je 50 der Untersuchungsflächen liegen in der Schwäbischen Alb, dem Hainich-Dün und der Schorfheide-Chorin. Im Mai 2011 und 2014 wurden zeitgleich Oberbodenproben in allen Regionen genommen und die mikrobielle Biomasse (C, N, P), Gemeinschaftsstruktur (Phospholipidfettsäuren) sowie Enzymaktivitäten des C-, N- und P-Kreislaufs bestimmt. Zwischen 2011 und 2014 hat sich die Landnutzungsintensität (LUI) einiger Flächen stark verändert, während die LUI anderer fast identisch blieb. Unsere zentrale Hypothese ist, dass die Veränderung der LUI, durch die direkte Nährstoffzufuhr über Dünger, zu Veränderungen in den mikrobiellen Bodeneigenschaften zwischen den Jahren geführt hat. Tatsächlich konnten Veränderungen der mikrobiellen Bodeneigenschaften im untersuchten Zeitraum detektiert werden. Ob diese direkt durch Veränderungen (V) der LUI, oder durch Variationen in Temperatur, Wasserhaltekapazität, pH-Wert und Pflanzenbestand erklärt werden können oder ob die Änderungen der Mikroorganismen (MO) durch die historischen Bedingungen (H) auf den Flächen beeinflusst wurden, wurde mittels hierarchischer Regressionsanalysen untersucht. Dabei gingen folgende Variablen in fünf Stufen in die Modelle ein: Umwelt: Temperatur (V), Wasserhaltekapazität (V), pH (H); Landmanagement: LUI (V, H); pH-Wertänderung: pH (V); Pflanzenfunktionen: Mykorrhizierungsintensität (V, H), spezifische Blattfläche (V, H), Blatt-P (V, H), Blatt-N (V, H) und Pflanzenbiomasse: Biomasse (V), Cellulose (V), Hemicellulosen (V), Lignin (V), Biomasse P (V), Biomasse N (V), Lignin:N (V). Dabei zeigte sich, dass die funktionellen Pflanzeneigenschaften, insbesondere der Blatt-P-Gehalt, einen erheblichen Einfluss auf die Veränderung der MO im Boden hatten. Am häufigsten signifikant war ihr Einfluss auf die MO der Schwäbischen Alb und des Hainich-Dün, während in der Schorfheide-Chorin die Änderung des pH-Wertes dominierte. Direkt wirkte sich die Änderung der LUI nur auf Pilze aus, nicht auf Bakterien und Enzymaktivitäten. Ob sich die LUI indirekt über die Pflanzen auf Enzyme und Bakterien auswirkte, ist Gegenstand weiterer Analysen

Comparative analysis of involvement of UGT1 and UGT2 splice variants of UDP-galactose transporter in glycosylation of macromolecules in MDCK and CHO cell lines

Nucleotide sugar transporters deliver nucleotide sugars into the Golgi apparatus and endoplasmic reticulum. This study aimed to further characterize mammalian UDP-galactose transporter (UGT) in MDCK and CHO cell lines. MDCK-RCAr and CHO-Lec8 mutant cell lines are defective in UGT transporter, although they exhibit some level of galactosylation. Previously, only single forms of UGT were identified in both cell lines, UGT1 in MDCK cells and UGT2 in CHO cells. We have identified the second UGT splice variants in CHO (UGT1) and MDCK (UGT2) cells. Compared to UGT1, UGT2 is more abundant in nearly all examined mammalian tissues and cell lines, but MDCK cells exhibit different relative distribution of both splice variants. Complementation analysis demonstrated that both UGT splice variants are necessary for N- and O-glycosylation of proteins. Both mutant cell lines produce chondroitin-4-sulfate at only a slightly lower level compared to wild-type cells. This defect is corrected by overexpression of both UGT splice variants. MDCK-RCAr mutant cells do not produce keratan sulfate and this effect is not corrected by either UGT splice variant, overexpressed either singly or in combination. Here we demonstrate that both UGT splice variants are important for glycosylation of proteins. In contrast to MDCK cells, MDCK-RCAr mutant cells may possess an additional defect within the keratan sulfate biosynthesis pathway