Evolving division of labor in a response threshold model

The response threshold model explains the emergence of division of labor (i.e., task specialization) in an unstructured population by assuming that the individuals have different propensities to work on different tasks. The incentive to attend to a particular task increases when the task is left unattended and decreases when individuals work on it. Here we derive mean-field equations for the stimulus dynamics and show that they exhibit complex attractors through period-doubling bifurcation cascades when the noise disrupting the thresholds is small. In addition, we show how the fixed threshold can be set to ensure specialization in both the transient and equilibrium regimes of the stimulus dynamics. However, a complete explanation of the emergence of division of labor requires that we address the question of where the threshold variation comes from, starting from a homogeneous population. We then study a structured population scenario, where the population is divided into a large number of independent groups of equal size, and the fitness of a group is proportional to the weighted mean work performed on the tasks during a fixed period of time. Using a winner-take-all strategy to model group competition and assuming an initial homogeneous metapopulation, we find that a substantial fraction of workers specialize in each task, without the need to penalize task switching

Interactions between glycerol, PEG-200 and (NH4)2 SO4 in the stability of heterologous cutinase

Cutinases (EC 3.1.1.74)are versatile enzymes that have hydrolytic activity on various esters [1]. The spacial structure and the catalytic site of the enzymes can be protected by chemical additives to promove the stability of the activity [2, 3]. The goal of this work was to improve the stability of a recombinant cutinase produced by Escherichia coli

Development of a flow injection method for monitoring cell membrane damage of wine lactic acid bacteria

A flow injection analysis (FIA) system was developed for the determination of phosphate efflux from wine lactic acid bacteria (Oenococus oeni and Lactobacillus hilgardii) as an indication of cell membrane damage. The system allowed the direct injection of the cell suspension, avoiding the filtration step, with minimumsample treatment andminimized reagent consumption. The developed system is characterized by a linear concentration zone between 3.2310 5 and 4.84104 mol L1 PO4 3 and repeatability better than 2.9%. Bacterial suspensions were exposed to a chemical stress with phenolic acids and injected in the FIAsystem at regular intervals. The extracellular concentration of phosphate was measured spectrophotometrically. The experimental results obtained indicate that hydroxycinnamic acids (p-coumaric, ferulic and caffeic) induced faster phosphate leakage rates than hydroxybenzoic acids (vanillic and p-hydroxybenzoic) in both strains tested, which could be related to their higher lipophilic character

Indigo degradation with purified laccases from Trametes hirsuta and Sclerotium rolfsii

The degradation of the textile dye indigo with purified laccases from the fungi Trametes hirsuta (THL1 and THL2) and Sclerotium rolfsii (SRL1) was studied. All laccases were able to oxidize indigo yielding isatin (indole-2,3-dione), which was further decomposed to anthranilic acid (2-aminobenzoic acid). Based on the oxygen consumption rate of the laccases during indigo degradation, a potential mechanism for the oxidation of indigo involving the step-wise abstraction of four electrons from indigo by the enzyme was suggested. Comparing the effect of the known redox-mediators acetosyringone, 1-hydroxybenzotriazole (HOBT) and 4-hydroxybenzenesulfonic acid (PHBS) on laccase-catalyzed degradation of indigo, we found a maximum of about 30% increase in the oxidation rate of indigo with SRL1 and acetosyringone. The particle size of indigo agglomerates after laccase treatment was influenced by the origin of the laccase preparation and by the incubation time. Diameter distributions were found to have one maximum and compared to the indigo particle size distribution of the control, for all laccases, the indigo agglomerates seemed to have shifted to smaller diameters. Bleaching of fabrics by the laccases (based on K/S values) correlated with the release of indigo degradation products. (C) 2001 Elsevier Science BY. All rights reserved

Ocorrência de plantas fôsseis do subgrupo Itararé, em Salto, SP

A small collection of plants from the basal part of the Itararé Subgroup (Late Paleozoic), near Salto, São Paulo State, contains Samaropsis, Cordaicarpus, Carpolithus, (?)Trigonocarpus, (?)Noeggerathiopsis and (?)Paracalamites, associated to fragments of smooth and striate stems, leaves and possible fructifications. It is probably the lowermost occurence of Late Paleozoic plant fossils in the nor then part of Paraná Basin

Climate- and fire-smart landscape scenarios call for redesigning protection regimes to achieve multiple management goals

Integrated management of biodiversity and ecosystem services (ES) in heterogeneous landscapes requires considering the potential trade-offs between conflicting objectives. The UNESCO's Biosphere Reserve zoning scheme is a suitable context to address these trade-offs by considering multiple management zones that aim to minimise conflicts between management objectives. Moreover, in Mediterranean ecosystems, management and planning also needs to consider drivers of landscape dynamics such as wildfires and traditional farming and forestry practices that have historically shaped landscapes and the biodiversity they host. In this study, we applied a conservation planning approach to prioritise the allocation of management zones under future landscape and climate scenarios. We tested different landscape management scenarios reflecting the outcomes of climate-smart and fire-smart policies. We projected the expected landscape dynamics and associated changes on the distribution of 207 vertebrate species, 4 ES and fire hazard under each scenario. We used Marxan with Zones to allocate three management zones, replicating the Biosphere Reserves zoning scheme (“Core area”, “Buffer zone” and “Transition area”) to address the various management objectives within the Biosphere Reserve. Our results show that to promote ES supply and biodiversity conservation, while also minimising fire hazard, the reserve will need to: i) Redefine its zoning, especially regarding Core Areas, which need a considerable expansion to help mitigate changes in biodiversity and accommodate ES supply under expected changes in climate and species distribution. ii) Revisit current management policies that will result in encroached landscapes prone to high intensity, uncontrollable wildfires with the potential to heavily damage ecosystems and compromise the supply of ES. Our results support that both climate- and fire-smart policies in the Meseta Ibérica can help develop multifunctional landscapes that help mitigate and adapt to climate change and ensure the best possible maintenance of biodiversity and ES supply under uncertain future climate conditions.This study was supported by national funds - Portuguese Foundation for Science and Technology, under the “FirESmart” project (PCIF/MOG/0083/2017), and the project UIDB/04033/2020. CCS is supported by the “Financiamento Programático” UIDP/04050/2020 funded by national funds through the FCT I.P. VH was funded by the Junta de Andalucía through an Emergia contract (EMERGIA20_00135). AR is supported by ‘Juan de la Cierva’ fellowship program funded by the Spanish Ministry of Science and Innovation (IJC2019-041033-I). ÂS received support from the Portuguese Foundation for Science and Technology (FCT) through Ph.D. Grant SFRH/BD/132838/2017, funded by the Ministry of Science, Technology and Higher Education, and by the European Social Fund - Operational Program Human Capital within the 2014–2020 EU Strategic Framework.info:eu-repo/semantics/publishedVersio