Structure and function of natural sulphide-oxidizing microbial mats under dynamic input of light and chemical energy

We studied the interaction between phototrophic and chemolithoautotrophic sulphide-oxidizing microorganisms in natural microbial mats forming in sulphidic streams. The structure of these mats varied between two end-members: one characterized by a layer dominated by large sulphur-oxidizing bacteria (SOB; mostly Beggiatoa-like) on top of a cyanobacterial layer (B/C mats) and the other with an inverted structure (C/B mats). C/B mats formed where the availability of oxygen from the water column was limited (<5 mu M). Aerobic chemolithotrophic activity of the SOB depended entirely on oxygen produced locally by cyanobacteria during high light conditions. In contrast, B/C mats formed at locations where oxygen in the water column was comparatively abundant (445 mu M) and continuously present. Here SOB were independent of the photosynthetic activity of cyanobacteria and outcompeted the cyanobacteria in the uppermost layer of the mat where energy sources for both functional groups were concentrated. Outcompetition of photosynthetic microbes in the presence of light was facilitated by the decoupling of aerobic chemolithotrophy and oxygenic phototrophy. Remarkably, the B/C mats conserved much less energy than the C/B mats, although similar amounts of light and chemical energy were available. Thus ecosystems do not necessarily develop towards optimal energy usage. Our data suggest that, when two independent sources of energy are available, the structure and activity of microbial communities is primarily determined by the continuous rather than the intermittent energy source, even if the time-integrated energy flux of the intermittent energy source is greater

Assessment of Poly(ADP-ribose) Polymerase1 (PARP1) expression and activity in cells purified from blood and milk of dairy cattle

Poly(ADP-ribosyl)ation (PAR) is a post-translational protein modification catalysed by enzyme member of the poly(ADP-ribose) polymerases (PARPs) family. The activation of several PARPs is triggered by DNA strand breakage and the main PARP enzyme involved in this process is PARP1. Besides its involvement in DNA repair, PARP1 is involved in several cellular processes including transcription, epigenetics, chromatin re-modelling as well as in the maintenance of genomic stability. Moreover, several studies in human and animal models showed PARP1 activation in various inflammatory disorders. The aims of the study were (1) to characterize PARP1 expression in bovine peripheral blood mononuclear cells (PBMC) and (2) to evaluate PAR levels as a potential inflammatory marker in cells isolated from blood and milk samples following different types of infection, including mastitis. Our results show that (i) bovine PBMC express PARP1; (ii) lymphocytes exhibit higher expression of PARP1 than monocytes; (iii) PARP1 and PAR levels were higher in circulating PBMCs of infected cows; (iv) PAR levels were higher in cells isolated from milk with higher Somatic Cell Counts (SCC > 100,000 cells/mL) than in cells from milk with low SCCs. In conclusion, these findings suggest that PARP1 is activated during mastitis, which may prove to be a useful biomarker of mastitis

Achtergrondstudie bij de subsidies voor de biologische land- en tuinbouw in Vlaanderen

In opdracht van de Vlaamse overheid heeft het Louis Bolk Instituut, samen met het Instituut voor landbouw- en visserijonderzoek (ILVO), een studie uitgevoerd naar de bedrijfseconomische gevolgen van de omschakeling van gangbare naar biologische landbouw. Aanleiding voor de studie waren een mogelijke herziening van de hoogte van de overheidssubsidie die biologische landbouwers in Vlaanderen hiervoor ontvangen en het geringe aantal omschakelende agrariërs. Conclusie van de studie is dat voor veel bedrijven omschakeling naar biologische landbouw een rendabel alternatief kan vormen. De studie bevestigt tevens een aantal fundamentele kwetsbaarheden en obstakels. Transitiekosten (het vergaren van nieuwe kennis en marktcontacten, de afzet van de producten en voor sommige bedrijven desinvesteringen tijdens de overgangsperiode) kunnen een groot obstakel vormen voor omschakeling omdat deze transitiekosten pas na vele jaren worden terugverdiend. Daarnaast kan het risico op marktfalen goed bedrijfsresultaat in de weg staan. Deze kwetsbaarheden en obstakels manifesteren zich vooral op bedrijfsniveau waardoor ze moeilijker toewijsbaar worden naar teeltniveau. Een van de aanbevelingen is daarom om (ook) instrumenten te ontwikkelen die de overgangskosten en het risico op marktfalen verminderen. Doordat omschakeling voor veel bedrijven een aantrekkelijke optie lijkt en belangrijke kostencomponenten zich vooral op bedrijfsniveau manifesteren is een blijvende en op hectarebasis teruggebrachte ondersteuningspremie voor biologische landbouw nog slechts beperkt te verantwoorden. Aangezien prijzen continue wisselen en de beschikbaarheid van betrouwbare gegevens beperkt is, is ook een ‘beslissingsondersteunend rekenmodel’ opgeleverd waarmee berekeningen gemakkelijk later opnieuw gedaan kunnen worden

The Dilemma of Agricultural Credit Policy in Brazil

Brazilian policy makers have played an active role in agricultural credit policy during the past 25 years. Many rules, regulations, policies and programs have been employed to increase the quantity and reduce the cost of agricultural credit. In some years, the amount of new loans made approached the value of agricultural output. Doubts exist about the extent to which expanded credit supplies accelerated technological change, expanded output and improved rural incomes. Large farmers absorbed a large share of the total credit. Interest rate constraints appear to have contributed to this concentration in credit distribution. The massive amount of subsidies involved in the credit program contributed to a need to reformulate credit and macroeconomic policies in the 1980s. The volume of new loans made subsequently fell sharply. In spite of acre than two decades of government involvement, Brazilian farmers are no closer to having a reliable, self-sustaining supply of agricultural credit today than they did in the early 1960's when the government began its heavy intervention

A Neural-Symbolic Cognitive Agent for Online Learning and Reasoning

In real-world applications, the effective integration of learning and reasoning in a cognitive agent model is a difficult task. However, such integration may lead to a better understanding, use and construction of more realistic models. Unfortunately, existing models are either oversimplified or require much processing time, which is unsuitable for online learning and reasoning. Currently, controlled environments like training simulators do not effectively integrate learning and reasoning. In particular, higher-order concepts and cognitive abilities have many unknown temporal relations with the data, making it impossible to represent such relationships by hand. We introduce a novel cognitive agent model and architecture for online learning and reasoning that seeks to effectively represent, learn and reason in complex training environments. The agent architecture of the model combines neural learning with symbolic knowledge representation. It is capable of learning new hypotheses from observed data, and infer new beliefs based on these hypotheses. Furthermore, it deals with uncertainty and errors in the data using a Bayesian inference model. The validation of the model on real-time simulations and the results presented here indicate the promise of the approach when performing online learning and reasoning in real-world scenarios, with possible applications in a range of areas