Agro-landerij: een moderne, regionale samenwerking

Het project regionaal gemengd bedrijf Zuidoost Drenthe is gericht op het maken van een businessplan voor een vergaande samenwerking tussen akkerbouwers en veehouders in zuidoost Drenthe, gebaseerd op specialisatie in de bedrijfsvoering. Het uiteindelijk doel is het opzetten van het Nieuw Gemengd Bedrijf, waarin (lokale) ondernemers – die in verschillende takken van sport opereren – en bewoners van het gebied samenwerken. Kortom, samenwerkingsvormen op het gebied van voer, energie, mest en recreatie (beleving). Nieuwe vormen van landbouw vragen om innovatie, samenwerken en risicospreiding, om mee te kunnen gaan in de tijd en klaar te zijn voor de toekomst. De economische structuren vragen erom en de landbouw is in zuidoost Drenthe een belangrijke drager van de economie

Sex differences in renin-angiotensin-aldosterone system affect extracellular volume in healthy subjects

Several studies reported sex differences in aldosterone. It is unknown whether these differences are associated with differences in volume regulation. Therefore we studied both aldoste

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

The effect of oxygen, pH and organic carbon on soil-layer specific denitrifying capacity in acid coniferous forest.

Emissions of

Spatial variation in net nitrate production in an N-saturated coniferous forest soil.

In this study the spatial variation in nitrate and ammonium production was investigated within a Scots pine forest soil. Geostatistical analysis using isopleths was used to determine spatial clustering of biological activity. The effect of inhibiting and limiting substances was tested to explain locally low nitrification. Nitrate and ammonium were determined in leachates from intact soil cores, collected from a 20 × 20

Microphytobenthos as a source of labile organic matter for denitrifying microbes

International audienceNitrogen loads in natural waters remain elevated in populated and agricultural areas with serious impact on estuarine and coastal ecosystems. Intertidal sediments can play a significant role in attenuating the high nitrogen levels in water via microbial nitrate reduction, in general dominated by denitrification. These heterotrophic processes are heavily mediated by both the quantity and quality of organic matter available. Benthic microalgae were experimentally investigated as organic carbon source for denitrifying microbes in intertidal mudflat sediments from the Seine Estuary (France). Dry microphytobenthos (including algae and their extracellular polymeric substances) were added to sediments and nitrate reduction rates were monitored over a two-week period using anoxic controlled flow-through reactor approach. Our results show that microphytobenthos addition resulted in significantly higher nitrate reduction (67–332% increase), highly related to the added amount of microphytobenthos. Moreover, increase of the low molecular weight carbohydrates consumption (11–39%) highlight the measurable contribution of extracellular polymeric substances to the carbon consumption during nitrate reduction. The addition of microphytobenthos increased the abundance of nitrite reductase genes, especially those encoding the nirS gene (43–152% increase) while nitrous oxide reductase genes (nosZ gene) remained constant. Microphytobenthos appeared to favor complete denitrification as suggested by an increase in nirS and a decrease in clade II nosZ gene copy numbers. This study confirms experimentally the assumption that microbes use microalgae and particularly labile extracellular polymeric substances as a carbon substrate for nitrate reduction. These results reinforce the impact played by microphytobenthos in intertidal mudflats by highlighting their role on denitrifying microbes and nitrate removal from water

Coexistence of aerobic chemotrophic and anaerobic phototrophic sulfur bacteria under oxygen limitation

The aerobic chemotrophic sulfur bacterium Thiobacillus thioparus T5 and the anaerobic phototrophic sulfur bacterium Thiocapsa roseopersicina M1 were co-cultured in continuously illuminated chemostats at a dilution rate of 0.05 h(-1). Sulfide was the only externally supplied electron donor, and oxygen and carbon dioxide served as electron acceptor and carbon source, respectively. Steady states were obtained with oxygen supplies ranging from non-limiting amounts (1.6 mol O-2 per mol sulfide, resulting in sulfide limitation) to severe limitation (0.65 mol O-2 per mol sulfide). Under sulfide limitation Thiocapsa was competitively excluded by Thiobacillus and washed out. Oxygen/sulfide ratios between 0.65 and 1.6 resulted in stable coexistence. It could be deduced that virtually all sulfide was oxidized by Thiobacillus. The present experiments showed that Thiocapsa is able to grow phototrophically on the partially oxidized products of Thiobacillus. In pure Thiobacillus cultures in steady state extracellular zerovalent sulfur accumulated. in contrast to mixed cultures. This suggests that a soluble form of sulfur at the oxidation state of elemental sulfur is formed by Thiobacillus as intermediate. As a result, under oxygen limitation colorless sulfur bacteria and purple sulfur bacteria do not competitively exclude each other but can coexist. It was shown that its ability to use partially oxidized sulfur compounds, formed under oxygen limiting conditions by Thiobacillus, helps explain the bloom formation of Thiocapsa in marine microbial mats.</p

Coexistence of aerobic chemotrophic and anaerobic phototrophic sulfur bacteria under oxygen limitation

The aerobic chemotrophic sulfur bacterium Thiobacillus thioparus T5 and the anaerobic phototrophic sulfur bacterium Thiocapsa roseopersicina M1 were co-cultured in continuously illuminated chemostats at a dilution rate of 0.05 h(-1). Sulfide was the only externally supplied electron donor, and oxygen and carbon dioxide served as electron acceptor and carbon source, respectively. Steady states were obtained with oxygen supplies ranging from non-limiting amounts (1.6 mol O-2 per mol sulfide, resulting in sulfide limitation) to severe limitation (0.65 mol O-2 per mol sulfide). Under sulfide limitation Thiocapsa was competitively excluded by Thiobacillus and washed out. Oxygen/sulfide ratios between 0.65 and 1.6 resulted in stable coexistence. It could be deduced that virtually all sulfide was oxidized by Thiobacillus. The present experiments showed that Thiocapsa is able to grow phototrophically on the partially oxidized products of Thiobacillus. In pure Thiobacillus cultures in steady state extracellular zerovalent sulfur accumulated. in contrast to mixed cultures. This suggests that a soluble form of sulfur at the oxidation state of elemental sulfur is formed by Thiobacillus as intermediate. As a result, under oxygen limitation colorless sulfur bacteria and purple sulfur bacteria do not competitively exclude each other but can coexist. It was shown that its ability to use partially oxidized sulfur compounds, formed under oxygen limiting conditions by Thiobacillus, helps explain the bloom formation of Thiocapsa in marine microbial mats.</p

Temporal and spatial variation of nitrogen transformations in a coniferous forest soils.

Forest soils show a great degree of temporal and spatial variation of nitrogen mineralization. The aim of the present study was to explain temporal variation in nitrate leaching from a nitrogen-saturated coniferous forest soil by potential nitrification, mineralization rates and nitrate uptake by roots. Variation in nitrate production in time and space, between the different organic horizons, has been related to temperature, moisture content, substrate availability and pH. Temporal variation in concentrations of nitrate and ammonium in the forest floor was significant during a one-year cycle, when randomly taken samples were pooled. Nitrogen concentrations differed between the different organic horizons with highest concentrations found in the litter layer, decreasing with increasing depth. Ammonium concentrations always exceeded nitrate concentrations by a factor ten, indicating that ammonium was not limiting nitrification. Nitrification potential, the nitrate production at field moisture at 25°C, was highest in the litter layer, lower in the fragmentation layer and hardly measurable in the mineral soil. Uptake of nitrate by roots and changes in mineralization rates turned out to be unimportant to explain variation in time, as seasonal fluctuations seem to be less important than spatial variation. We found that horizontal spatial variation in potential nitrate production, leaching of nitrate and nitrogen concentrations from non-pooled field samples was higher than variation in time. All this reflects the actual spatial variation in the field, which is not explained by differences in moisture content or temperature. Overall neither pH nor substrate availability could explain this observed variation, however, local variation in microsites may be responsible for small-scale spatial variation. Allelopathic compounds and/or the composition of the microbial community are suggested as factors possibly affecting nitrate production. (C) 2000 Elsevier Science Ltd