Endophytic bacteria associated with spontaneous legumes in arid zones of Tunisia: Genetic diversity, metabolic functionalities and potential application to mitigate the impact of climate change

Legumes naturally adapted to harsh climate environments represent a new source of plant growth promoting (PGP) bacteria that can be used to improve crop resilience to climate change. However, the diversity and functionality of endophytic bacteria associated with endemic wild legumes in Tunisia are almost unknown. To study the taxonomic and functional diversity of these species, we conducted a study on root nodules of 15 spontaneous legumes, some of which studied for the first time, growing in three different Tunisian bioclimates (arid, semi-arid and Saharan). More than 210 strains, corresponding to 78 different phylotypes, were isolated. Sequencing of the 16S rDNA revealed the presence of rhizobial isolates belonging to the genera: Rhizobium, Sinorhizobium, Bradyrhizobium, Mesorhizobium, Neorhizobium, Agrobacterium, Phyllobacterium, Cupriavidus and Burkholderia. Other non-rhizobial bacteria assigned to Microbacterium, Pseudomonas, Paenibacillus, Starkeya, Kocuria among others, were also obtained. In addition, the nucleotide similarity of housekeeping genes suggested the presence of new species in our collection. Indeed, the genomic sequencing analysis identified a new species of Mesorhizobium (PRJNA800673), a microsymbiont of Retama raetam, which is one of the most important Tunisian shrubs. Regarding PGP-screening abilities, several strains stood out for possessing several PGP traits, phosphate solubilization, indole acetic acid and siderophores production, along with high tolerance to abiotic stress (> 45°C; > 0.4M NaCl). For rhizobia, whole genome sequencing of the Saharan isolate Sinorhizobium meliloti IRAM:0087 (PRJNA842649) revealed the existence of several gene clusters coding for different PGP activities, rhizosphere competitiveness and stress tolerance, some of which were confirmed in vitro assays. Based on the evaluation of the PGP potential of non-rhizobial strains, three bacteria P. salinitolerans, P. turukhanskensis and Starkeya sp. were selected to improve Pisum sativum, a cold season crop, tolerance to a heat stress event. Our preliminary results suggest that endophytic isolates from arid legumes represent a promising resource of biofertilizers/biostimulants to increase plant resilience to heat stress. Future studies to explore the adaptative responses of these endophytes to different types of stress will allow to better understand their stress tolerance mechanisms and contribute to select strains for nature-based solutions towards the establishment of new agricultural technologies in drylands

Evaluating the effect of various bacterial consortia isolated from arid wild legumes on heat stress tolerance of Pisum sativum

High-temperature stress affects the growth and developmental process of cool-season grain legumes. We hypothesized that endophytic bacteria associated with arid plants could be a potential resource to ensure the tolerance of cold-season legumes to high temperature stress events. To test our hypothesis, Phyllobacterium salinitolerans (PH), Starkeya sp. (ST) and Pseudomonas turukhanskensis (PS) endophytes of different spontaneous legumes localised in Tunisian arid regions were selected to evaluate their potential in improving Pisum sativum growth and pea-rhizobia symbiosis under a heat stress event. Three consortia (containing different combinations of endophytes) were used along with the pea microsymbiont Rhizobium leguminosarum 128C53 (WT) or with its ΔacdS mutant derivative (MT) (Ma et al., 2003). Uninoculated plants without or with nitrogen supplement were used as negative (NC) or positive controls (PC), respectively. The heat stress event was applied 2 weeks after sowing for a period of 2 weeks with consecutive cycles of 30-35°C/16h and 20°C/8h. Interestingly, the shoot dry weight (SDW) of all plants co-inoculated with WT and any of the consortia containing PH increased significantly compared to that of plants inoculated with WT alone. A similar effect was observed on the root dry weight (RDW) in the treatments WT+ST+PH and WT+PS+PH. On the other hand, the best results either in terms of SDW or RDW with the mutant strain was the treatment that included all endophytes (MT+ST+PS+PH), even overcoming all treatments inoculated with WT and equalling the PC. As expected, plants inoculated with the MT had a lower number of nodules (NN) compared to plants inoculated with WT, except for MT+ST+PS+PH with similar NN. A significant increase in the NN was observed in plants co-inoculated with WT+ST+PH and WT+PS+PH compared to those in WT. The highest total chlorophyll content was in WT+ST+PS, which was significantly different from all other treatments while no differences were observed in phenolic compounds content among the inoculated treatments. Overall, our results suggest that endophytic isolates from arid leguminous plants are good candidates for increasing the resilience of plants not adapted to heat stress

Performances des stations de pompages en irrigation : application aux forages de petits périmètres irrigués de la plaine de Kairouan (Tunisie) et impact des dysfonctionnements sur le prix de l'eau

International audienceLorsqu'une élévation de l'eau de nappes ou une mise en pression est nécessaire au fonctionnement des systèmes modernes d'irrigation dans un périmètre, on utilise presque exclusivement des pompes centrifuges. La facture énergétique représente donc une part importante du coût de l'eau. Or, le rendement de ces machines est très dépendant de leurs conditions de fonctionnement et de leur usure et toute déviation par rapport aux conditions optimales entraîne des surcoûts énergétiques importants. L'objectif est de proposer une méthodologie pour évaluer les performances de ces équipements. Des indicateurs accessibles (énergie unitaire, énergie volumique absorbée réelle, volume spécifique pompé, coefficient de volume spécifique pompé) sont définis et des valeurs de référence fournies à partir des données des constructeurs. Les différentes méthodes d'estimation des volumes pompés sont critiquées. Les tests proposés sur les données volumiques indiquent le type de mesure réalisé pour les volumes pompés ainsi que leur dérive dans le temps (utilisation du débit nominal, compteur volumétrique). Pour les mesures d'énergie, l'absence de synchronisation entre les relevés temporels et énergétiques implique de cumuler les données pour obtenir la puissance consommée - lors de conditions stables de fonctionnement des pompes et si chaque pompe dispose d'un compteur d'énergie. Un ensemble de 18 stations de pompage sur forage alimentant des petits périmètres irrigués de la plaine de Kairouan en Tunisie centrale a été testé. La vétusté des équipements peut engendrer des rendements très faibles dont la conséquence principale est une augmentation des coûts de pompage (consommation énergétique et surcoût de maintenance). Ce diagnostic met donc bien en évidence l'intérêt d'un suivi précis de chaque ouvrage. Les divergences observées dans les ratios entre les volumes pompés et l'énergie consommée par rapport à ceux attendus en conditions optimales de fonctionnement conduisent au raisonnement suivant : si les données obtenues sont justes, le dysfonctionnement provient de l'inadaptation de l'équipement hydroélectrique au fonctionnement hydraulique de l'installation ; ou bien si les données sont fausses, ce dysfonctionnement provient des erreurs de gestion des pompistes et les quantités d'eau pompées sont alors sous-estimées. Dans les deux cas, un surcoût est payé par l'Administration. Dans la moitié des stations, les surcoûts d'énergie dépassent 20 %, voire 50 % pour près du quart d'entre elles

The role of interacting social and institutional norms in stressed groundwater systems

Groundwater resources play an important role for irrigation, particularly in arid and semi-arid regions, where groundwater depletion poses a critical threat to agricultural production and associated local livelihoods. However, the relationship between groundwater use, farming, and poverty, particularly with regards to informal mechanisms of resources management, remains poorly understood. Here, we assess this relationship by developing a behavioural model of groundwater user groups, empirically grounded in the politically fragile context of Tunisia. The model integrates biophysical aquifer dynamics, institutional governance, and farmer decision-making, all of which are co-occurring under conditions of aquifer depletion and illicit groundwater extraction. The paper examines how community-level norms drive distributional outcomes of farmer behaviours and traces pathways of local system collapse - whether hydrogeological or financial. Through this model, we explore how varying levels of trust and leadership, ecological conditions, and agricultural strategies can delay or avoid collapse of the social-ecological system. Results indicate limits to collective action under path-dependent aquifer depletion, which ultimately leads to the hydrogeological collapse of groundwater user groups independent of social and institutional norms. Despite this inevitable hydrogeological collapse of user groups, the most common cause of water user group failure is bankruptcy, which is linked to the erosion of social norms regarding fee payment. Social and institutional norms, however, can serve to delay the financial collapse of user groups. In the politically fragile system of Tunisia, low levels of trust in government result in low social penalties for illicit water withdrawals. In the absence of alternative irrigation sources, this serves as a temporary buffer against income-poverty. These results highlight the need for polycentric coordination at the aquifer-level as well as income diversification beyond agriculture to sustain local livelihoods

Quantifying the micellar structure formed from hydrocarbon-fluorocarbon surfactants

Many technological formulations contain mixtures of surfactants, each contributing some distinct property. Characteristics of each surfactant are often modulated in the mixture, based on the interactions between the various components present. Here, the mixing of the hydrocarbon surfactant cetyltrimethyl ammonium bromide (C16TAB) and the fluorocarbon surfactant, Zonyl-FSN-100 with average chemical structure of C8F17C2H4 (OC2H4)9OH, is quantified, in particular, the size and shape of the micelles and their critical micelle concentration (CMC). The CMC data suggest there are specific interactions between the two components which are strongly antagonistic. Small-angle neutron scattering (SANS) has been used to quantify the size and shape of the micelle, and these data indicate that the single component FSN-100 forms disc-like micelles with a small aggregation number (~65) and the C16TAB forms globular, charged micelles with a larger aggregation number (135). The aggregation number of the mixed micelle is substantially greater than either of the pure species. Overall, a detailed study of CTAB, FSN-100 and their mixture systems will be presented in this paper

Nature’s contribution to people provided by pastoral systems across European, African, and Middle East Mediterranean countries: trends, approaches and gaps

Mediterranean pastoral systems are providers of a wide array of Nature’s Contribution to People (NCP). They are ‘complex systems’ characterized by limited resources and socio-economic dynamics currently threatened by climate and social changes. Despite a growing number of scientifc articles dealing with NCP, there is a high risk that the existing literature has left out the complexity of such systems. In the light of ongoing social, economic, and climatic changes in the Mediterranean basin, neglecting the complexity of pastoral systems can lead to signifcant research biases, missing the priorities afecting the stability and continuity of such systems. A combination of frameworks of analysis provided by the Millennium Ecosystem Assessment and by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services was applied to understand if and to what extent the complexity of Mediterranean pastoral systems has been considered in the available literature. Most of the 126 papers report studies conducted in the European Union zone (102 papers), with the majority in Spain (50). Fewer studies have been conducted in the Middle East (15 papers) and Africa zones (9 papers). Despite results confrming the importance of pastoral systems as providers of NCP, most of the eligible papers focused on regulating NCP. A lack of a multisectoral approach and integration of knowledge suggests that the complexity of Mediterranean pastoral systems has been overlooked by researchers. The creation of ‘hybrid knowledge’ bridging the expertise of diferent stakeholders could be the key ingredient to properly address the complexity of Mediterranean pastoral systems.This study was carried out with the support of project PACTORES (PAstoral ACTORs, ES, and Society as key elements of agro-pastoral systems in the Mediterranean), ERANETMED ‘EURO-MEDITERRANEAN Cooperation through ERANET joint activities and beyond’- Joint Transnational Call 2016 - Environmental challenges and solutions for vulnerable communities (ERANETMED2-72-303). We would like to thank the late Marco Toderi for his considerable help and inspiration and without whom this research would never have been possible. Open access funding provided by Università Politecnica delle Marche within the CRUI-CARE Agreement.info:eu-repo/semantics/publishedVersio

Sex differences in vascular endothelial function and health in humans: Impacts of exercise.

This brief review presents historical evidence for the purported impacts of male and female sex hormones on the vasculature in humans, including effects on macro- and micro-vascular function and health. Impacts of aging on hormonal changes and artery function are considered in the context of the menopause. Physiological data are presented alongside clinical outcomes from large trials, in an attempt to rationalise disparate findings along the bench-to-bedside continuum. Finally, the theoretical likelihood that exercise and hormone treatment may induce synergistic and/or additive vascular adaptations is developed in the context of recent laboratory studies that have compared male and female responses to training. Differences between men and women in terms of the impact of age and cardiorespiratory fitness on endothelial function are addressed. Ultimately, this review highlights the paucity of high quality and compelling evidence regarding the fundamental impact, in humans, of sex differences on arterial function and the moderating impacts of exercise on arterial function, adaptation and health at different ages in either sex. This article is protected by copyright. All rights reserved