Environmental, economic, and social sustainability in aquaculture: the aquaculture performance indicators.

Aquaculture is a rapidly growing food production technology, but there are significant concerns related to its environmental impact and adverse social effects. We examine aquaculture outcomes in a three pillars of sustainability framework by analyzing data collected using the Aquaculture Performance Indicators. Using this approach, comparable data has been collected for 57 aquaculture systems worldwide on 88 metrics that measure social, economic, or environmental outcomes. We first examine the relationships among the three pillars of sustainability and then analyze performance in the three pillars by technology and species. The results show that economic, social, and environmental outcomes are, on average, mutually reinforced in global aquaculture systems. However, the analysis also shows significant variation in the degree of sustainability in different aquaculture systems, and weak performance of some production systems in some dimensions provides opportunity for innovative policy measures and investment to further align sustainability objectives.

Nitrate modulates the physiological tolerance responses of the halophytic species Sarcocornia fruticosa to copper excess.

Coexistence impact of pollutants of different nature on halophytes tolerance to metal excess has not been thoroughly examined, and plant functional responses described so far do not follow a clear pattern. Using the Cu-tolerant halophyte Sarcocornia fruticosa as a model species, we conducted a greenhouse experiment to evaluate the impact of two concentration of copper (0 and 12 mM CuSO4) in combination with three nitrate levels (2, 14 and 50 mM KNO3) on plant growth, photosynthetic apparatus performance and ROS-scavenging enzymes system. The results revealed that S. fruticosa was able to grow adequately even when exposed to high concentrations of copper and nitrate. This response was linked to the plant capacity to uptake and retain a large amount of copper in its roots (up to 1500 mg kg-1 Cu), preventing its transport to aerial parts. This control of translocation was further magnified with nitrate concentration increment. Likewise, although Cu excess impaired S. fruticosa carbon assimilation capacity, the plant was able to downregulate its light-harvesting complexes function, as indicated its lowers ETR values, especially at 12 mM Cu + 50 mM NO3. This downregulation would contribute to avoid excess energy absorption and transformation. In addition, this strategy of avoiding excess energy was accompanied by the upregulation of all ROS-scavenging enzymes, a response that was further enhanced by the increase in nitrate concentration. Therefore, we conclude that the coexistence of nitrate would favor S. fruticosa tolerance to copper excess, and this effect is mediated by the combined activation of several tolerance mechanisms.

Exploring through the use of physiological and isotopic techniques the potential of a PGPR-based biofertilizer to improve nitrogen fertilization practices efficiency in strawberry cultivation.

The use of microorganisms as a biofertilizer in strawberry has focused mainly on pathogen biocontrol, which has led to the underestimation of the potential of microorganisms for the improvement of nutritional efficiency in this crop. A study was established to investigate the impact of a plant growth-promoting rhizobacteria (PGPR) based biofertilizer integrated by self-compatible stress tolerant strains with multiple PGP properties, including atmospheric nitrogen fixation, on strawberry (Fragaria × ananassa cv. Rociera) tolerance to N deficiency in terms of growth and physiological performance. After 40 days of nitrogen fertilization shortage, inoculated plants were able to maintain root development and fertility structures (i.e. fruits and flowers) at a level similar to plants properly fertilized. In addition, inoculation lessened the negative impact of nitrogen deficiency on leaves' dry weight and relative water content. This effect was mediated by a higher root/shoot ratio, which would have allowed them to explore larger volumes of soil for the acquisition of water. Moreover, inoculation was able to buffer up to 50% of the reduction in carbon assimilation capacity, due to its positive effect on the diffusion efficiency of CO2 and the biochemical capacity of photosynthesis, as well as on the activity of photosystem II light harvesting. Furthermore, the higher leaf C/N ratio and the maintained δ15N values close to control plants were related to positive bacterial effects at the level of the plant nutritional balance. Despite these positive effects, the application of the bacterial inoculum was unable to completely counteract the restriction of fertilization, being necessary to apply a certain amount of synthetic fertilizer for the strawberry nutrition. However, according to our results, the complementary effect of this PGPR-based biofertilizer could provide a higher efficiency in environmental and economic yields on this crop.

Plant Growth-Promoting Rhizobacteria Improve Rice Response to Climate Change Conditions.

Rice is one of the most important crops in the world and is considered a strategic crop for food security. Furthermore, the excessive use of chemical fertilizers to obtain high yields causes environmental problems. A sustainable alternative includes taking advantage of beneficial bacteria that promote plant growth. Here, we investigate the effect of five bacterial biofertilizers from halophytes on growth, and we investigate photosynthetic efficiency in rice plants grown under saline conditions (0 and 85 mmol L-1 NaCl) and future climate change scenarios, including increased CO2 concentrations and temperature (400/700 ppm and 25/+4 °C, respectively). Biofertilizers 1-4 increased growth by 9-64% in plants grown with and without salt in both CO2- temperature combinations, although there was no significant positive effect on the net photosynthetic rate of rice plants. In general, biofertilizer 1 was the most effective at 400 ppm CO2 and at 700 ppm CO2 +4 °C in the absence of salt. Inocula 1-5 also stimulated plant length at high CO2 levels without salt. Finally, the positive effect of biofertilization was attenuated in the plants grown under the interaction between salt and high CO2. This highlights the significance of studying biofertilization under stress interaction to establish the real potential of biofertilizers in the context of climate change conditions.

Culturomics and Circular Agronomy: Two Sides of the Same Coin for the Design of a Tailored Biofertilizer for the Semi-Halophyte Mesembryanthemum crystallinum.

According to the EU, the global consumption of biomass, fossil fuels, metals, and minerals is expected to double by 2050, while waste will increase by 70%. In this context, the Circular Economy Action Plan (CEAP) intends to integrate development and sustainability. In this regard, tailored biofertilizers based on plant growth-promoting bacteria (PGPB) can improve plant yield with fewer inputs. In our project, an autochthonous halophyte of the Andalusian marshes, namely Mesembryanthemum crystallinum, was selected for its interest as a source of pharmaceuticals and nutraceuticals. The aim of this work was to use a culturomics approach for the isolation of specific PGPB and endophytes able to promote plant growth and, eventually, modulate the metabolome of the plant. For this purpose, a specific culture medium based on M. crystallinum biomass, called Mesem Agar (MA), was elaborated. Bacteria of three compartments (rhizosphere soil, root endophytes, and shoot endophytes) were isolated on standard tryptone soy agar (TSA) and MA in order to obtain two independent collections. A higher number of bacteria were isolated on TSA than in MA (47 vs. 37). All the bacteria were identified, and although some of them were isolated in both media (Pseudomonas, Bacillus, Priestia, Rosellomorea, etc.), either medium allowed the isolation of specific members of the M. crystallinum microbiome such as Leclercia, Curtobacterium, Pantoea, Lysinibacillus, Mesobacillus, Glutamicibacter, etc. Plant growth-promoting properties and extracellular degrading activities of all the strains were determined, and distinct patterns were found in both media. The three best bacteria of each collection were selected in order to produce two different consortia, whose effects on seed germination, root colonization, plant growth and physiology, and metabolomics were analyzed. Additionally, the results of the plant metabolome revealed a differential accumulation of several primary and secondary metabolites with pharmaceutical properties. Overall, the results demonstrated the feasibility of using "low cost media" based on plant biomass to carry out a culturomics approach in order to isolate the most suitable bacteria for biofertilizers. In this way, a circular model is established in which bacteria help plants to grow, and, in turn, a medium based on plant wastes supports bacterial growth at low prices, which is the reason why this approach can be considered within the model of "circular agronomy".

Nodule Synthetic Bacterial Community as Legume Biofertilizer under Abiotic Stress in Estuarine Soils.

Estuaries are ecologically important ecosystems particularly affected by climate change and human activities. Our interest is focused on the use of legumes to fight against the degradation of estuarine soils and loss of fertility under adverse conditions. This work was aimed to determine the potential of a nodule synthetic bacterial community (SynCom), including two Ensifer sp. and two Pseudomonas sp. strains isolated from Medicago spp. nodules, to promote M. sativa growth and nodulation in degraded estuarine soils under several abiotic stresses, including high metal contamination, salinity, drought and high temperature. These plant growth promoting (PGP) endophytes were able to maintain and even increase their PGP properties in the presence of metals. Inoculation with the SynCom in pots containing soil enhanced plant growth parameters (from 3- to 12-fold increase in dry weight), nodulation (from 1.5- to 3-fold increase in nodules number), photosynthesis and nitrogen content (up to 4-fold under metal stress) under all the controlled conditions tested. The increase in plant antioxidant enzymatic activities seems to be a common and important mechanism of plant protection induced by the SynCom under abiotic stress conditions. The SynCom increased M. sativa metals accumulation in roots, with low levels of metals translocation to shoots. Results indicated that the SynCom used in this work is an appropriate ecological and safe tool to improve Medicago growth and adaptation to degraded estuarine soils under climate change conditions.

Improving Grapevine Heat Stress Resilience with Marine Plant Growth-Promoting Rhizobacteria Consortia.

Amid climate change, heatwave events are expected to increase in frequency and severity. As a result, yield losses in viticulture due to heatwave stress have increased over the years. As one of the most important crops in the world, an eco-friendly stress mitigation strategy is greatly needed. The present work aims to evaluate the physiological fitness improvement by two marine plant growth-promoting rhizobacteria consortia in Vitis vinifera cv. Antão Vaz under heatwave conditions. To assess the potential biophysical and biochemical thermal stress feedback amelioration, photochemical traits, pigment and fatty acid profiles, and osmotic and oxidative stress biomarkers were analysed. Bioaugmented grapevines exposed to heatwave stress presented a significantly enhanced photoprotection capability and higher thermo-stability, exhibiting a significantly lower dissipation energy flux than the non-inoculated plants. Additionally, one of the rhizobacterial consortia tested improved light-harvesting capabilities by increasing reaction centre availability and preserving photosynthetic efficiency. Rhizobacteria inoculation expressed an osmoprotectant promotion, revealed by the lower osmolyte concentration while maintaining leaf turgidity. Improved antioxidant mechanisms and membrane stability resulted in lowered lipid peroxidation product formation when compared to non-inoculated plants. Although the consortia were found to differ significantly in their effectiveness, these findings demonstrate that bioaugmentation induced significant heatwave stress tolerance and mitigation. This study revealed the promising usage of marine PGPR consortia to promote plant fitness and minimize heatwave impacts in grapevines.

Stimulation of PGP Bacteria on the Development of Seeds, Plants and Cuttings of the Obligate Halophyte Arthrocaulon (Arthrocnemum) macrostachyum (Moric.) Piirainen & G. Kadereit.

The Earth is undergoing alterations at a high speed, which causes problems such as environmental pollution and difficulty in food production. This is where halophytes are interesting, due to their high potential in different fields, such as remediation of the environment and agriculture. For this reason, it is necessary to deepen the knowledge of the development of halophytes and how plant growth-promoting bacteria (PGP) can play a fundamental role in this process. Therefore, in this work were tested the effects of five PGP bacteria on its rhizosphere and other endophytic bacteria at different concentrations of NaCl on seed germination, plant growth (0 and 171 mM) and cutting growth (0 mM) of Arthrocaulon macrostachyum. The growth promotion in this strict halophyte is highlighted due to the presence of PGP bacteria and the fact that no salt is needed. Thus, without salt, the bacterial strains Kocuria polaris Hv16, Pseudarthrobacter psychrotolerans C58, and Rahnella aceris RTE9 enhanced the biomass production by more than 60% in both stems and roots. Furthermore, germination was encouraged by more than 30% in the presence of both R. aceris RTE9 and K. polaris Hv16 at 171 mM NaCl; the latter also had a biocontrol effect on the fungi that grew on the seeds. Additionally, for the first time in cuttings of this perennial species, the root biomass was improved thanks to the consortium of K. polaris Hv16 and P. psychrotolerans C58. Finally, this study demonstrates the potential of PGPs for optimising the development of halophytes, either for environmental or agronomic purposes.

A Culturomics-Based Bacterial Synthetic Community for Improving Resilience towards Arsenic and Heavy Metals in the Nutraceutical Plant Mesembryanthemum crystallinum.

Plant-growth-promoting bacteria (PGPB) help plants thrive in polluted environments and increase crops yield using fewer inputs. Therefore, the design of tailored biofertilizers is of the utmost importance. The purpose of this work was to test two different bacterial synthetic communities (SynComs) from the microbiome of Mesembryanthemum crystallinum, a moderate halophyte with cosmetic, pharmaceutical, and nutraceutical applications. The SynComs were composed of specific metal-resistant plant-growth-promoting rhizobacteria and endophytes. In addition, the possibility of modulating the accumulation of nutraceutical substances by the synergetic effect of metal stress and inoculation with selected bacteria was tested. One of the SynComs was isolated on standard tryptone soy agar (TSA), whereas the other was isolated following a culturomics approach. For that, a culture medium based on M. crystallinum biomass, called Mesem Agar (MA), was elaborated. Bacteria of three compartments (rhizosphere soil, root endophytes, and shoot endophytes) were isolated on standard TSA and MA media, stablishing two independent collections. All bacteria were tested for PGP properties, secreted enzymatic activities, and resistance towards As, Cd, Cu, and Zn. The three best bacteria from each collection were selected in order to produce two different consortiums (denominated TSA- and MA-SynComs, respectively), whose effect on plant growth and physiology, metal accumulation, and metabolomics was evaluated. Both SynComs, particularly MA, improved plant growth and physiological parameters under stress by a mixture of As, Cd, Cu, and Zn. Regarding metal accumulation, the concentrations of all metals/metalloids in plant tissues were below the threshold for plant metal toxicity, indicating that this plant is able to thrive in polluted soils when assisted by metal/metalloid-resistant SynComs and could be safely used for pharmaceutical purposes. Initial metabolomics analyses depict changes in plant metabolome upon exposure to metal stress and inoculation, suggesting the possibility of modulating the concentration of high-value metabolites. In addition, the usefulness of both SynComs was tested in a crop plant, namely Medicago sativa (alfalfa). The results demonstrate the effectiveness of these biofertilizers in alfalfa, improving plant growth, physiology, and metal accumulation.

Antimicrobial and Antibiofilm Effect of 4,4'-Dihydroxy-azobenzene against Clinically Resistant Staphylococci.

The spread of antibiotic resistance among human and animal pathogens is one of the more significant public health concerns. Moreover, the restrictions on the use of particular antibiotics can limit the options for the treatment of infections in veterinary clinical practice. In this context, searching for alternative antimicrobial substances is crucial nowadays. In this study, 4,4'-dihydroxy-azobenzene (DHAB) was tested for its potential in vitro as an antimicrobial agent against two relevant human and animal pathogens, namely Staphylococcus aureus and Staphylococcus pseudintermedius. The values of minimal inhibitory concentration (MIC) were 64 and 32 mg/L respectively, and they comparable to other azo compounds of probed antimicrobial activity. In addition, the minimal bactericidal concentrations (MCB) were 256 and 64 mg/L. The mechanism by which DHAB produces toxicity in staphylococci has been investigated. DHAB caused membrane damage as revealed by the increase in thiobarbituric acid reactive substances (TBARS) such as malondialdehyde. Furthermore, differential induction of the enzymes peroxidases and superoxide dismutase in S. aureus and S. pseudintermedius suggested their prevalent role in ROS-scavenging due to the oxidative burst induced by this compound in either species. In addition, this substance was able to inhibit the formation of biofilms by both bacteria as observed by colorimetric tests and scanning electron microscopy. In order to assess the relevance of DHAB against clinical strains of MRSA, 10 clinical isolates resistant to either methicillin or daptomycin were assayed; 80% of them gave values of CMI and CMB similar to those of the control S. aureus strain. Finally, cutaneous plasters containing a composite formed by an agar base supplemented with DHAB were designed. These plasters were able to inhibit in vitro the growth of S. aureus and S. pseudintermedius, particularly the later, and this suggests that this substance could be a promising candidate as an alternative to antibiotics in the treatment of animal skin infections, as it has been proven that the toxicity of this substance is very low particularly at a dermal level.

Enhanced legume growth and adaptation to degraded estuarine soils using Pseudomonas sp. nodule endophytes.

The joint estuary of Tinto and Odiel rivers (SW Spain) is one of the most degraded and polluted areas in the world and its recovery is mandatory. Legumes and their associated bacteria are recommended sustainable tools to fight against soils degradation and loss of fertility due to their known positive impacts on soils. The aim of this work was to isolate and characterize plant growth promoting nodule endophytes (PGPNE) from inside nodules of Medicago spp. naturally growing in the estuary of the Tinto and Odiel Rivers and evaluate their ability to promote legume adaptation in degraded soils. The best rhizobia and non-rhizobia among 33 endophytes were selected based on their plant growth promoting properties and bacterial enzymatic activities. These strains, identified as Pseudomonas sp. N4, Pseudomonas sp. N8, Ensifer sp. N10 and Ensifer sp. N12, were used for in vitro studies using Medicago sativa plants. The effects of individual or combined inoculation on seed germination, plant growth and nodulation were studied, both on plates and pots containing nutrient-poor soils and moderately contaminated with metals/loids from the estuary. In general, inoculation with combinations of rhizobia and Pseudomonas increased plant biomass (up to 1.5-fold) and nodules number (up to 2-fold) compared to single inoculation with rhizobia, ameliorating the physiological state of the plants and helping to regulate plant stress mechanisms. The greatest benefits were observed in plants inoculated with the consortium containing the four strains. In addition, combined inoculation with Ensifer and Pseudomonas increased As and metals accumulation in plant roots, without significant differences in shoot metal accumulation. These results suggest that PGPNE are useful biotools to promote legume growth and phytostabilization potential in nutrient-poor and/or metals contaminated estuarine soils.

Beyond the Glycaemic Control of Dapagliflozin: Impact on Arterial Stiffness and Macroangiopathy.

Dapagliflozin is a selective sodium-glucose cotransporter 2 inhibitor (SGLT2i) indicated for the treatment of type 2 diabetes mellitus (T2DM), heart failure with reduced ejection fraction and chronic kidney disease. In all indications, treatment can be initiated in adults with estimated glomerular filtration rate of at least 25 mL/min/1.73 m2. As monotherapy or as an additive therapy, dapagliflozin has been shown to promote better glycaemic control, associated with a reduction in body weight and blood pressure in a wide range of patients. In addition, dapagliflozin has a positive impact on arterial stiffness, helps to control the lipid profile and contributes to a reduced risk of cardiovascular complications. This article reviews the current scientific evidence on the role of dapagliflozin in cardiovascular risk factors including arterial stiffness, cardiovascular disease and heart failure in patients with T2DM, with the aim of helping to translate this evidence into clinical practice. The underuse of SGLT2i in actual clinical practice is also discussed.

Role of Nodulation-Enhancing Rhizobacteria in the Promotion of Medicago sativa Development in Nutrient-Poor Soils.

Legumes are usually used as cover crops to improve soil quality due to the biological nitrogen fixation that occurs due to the interaction of legumes and rhizobia. This symbiosis can be used to recover degraded soils using legumes as pioneer plants. In this work, we screened for bacteria that improve the legume-rhizobia interaction in nutrient-poor soils. Fourteen phosphate solubilizer-strains were isolated, showing at least three out of the five tested plant growth promoting properties. Furthermore, cellulase, protease, pectinase, and chitinase activities were detected in three of the isolated strains. Pseudomonas sp. L1, Chryseobacterium soli L2, and Priestia megaterium L3 were selected to inoculate seeds and plants of Medicago sativa using a nutrient-poor soil as substrate under greenhouse conditions. The effects of the three bacteria individually and in consortium showed more vigorous plants with increased numbers of nodules and a higher nitrogen content than non-inoculated plants. Moreover, bacterial inoculation increased plants' antioxidant activities and improved their development in nutrient-poor soils, suggesting an important role in the stress mechanisms of plants. In conclusion, the selected strains are nodulation-enhancing rhizobacteria that improve leguminous plants growth and nodulation in nutrient-poor soils and could be used by sustainable agriculture to promote plants' development in degraded soils.

Improved Medicago sativa Nodulation under Stress Assisted by Variovorax sp. Endophytes.

Legumes are the recommended crops to fight against soil degradation and loss of fertility because of their known positive impacts on soils. Our interest is focused on the identification of plant-growth-promoting endophytes inhabiting nodules able to enhance legume growth in poor and/or degraded soils. The ability of Variovorax paradoxus S110T and Variovorax gossypii JM-310T to promote alfalfa growth in nutrient-poor and metal-contaminated estuarine soils was studied. Both strains behaved as nodule endophytes and improved in vitro seed germination and plant growth, as well as nodulation in co-inoculation with Ensifer medicae MA11. Variovorax ameliorated the physiological status of the plant, increased nodulation, chlorophyll and nitrogen content, and the response to stress and metal accumulation in the roots of alfalfa growing in degraded soils with moderate to high levels of contamination. The presence of plant-growth-promoting traits in Variovorax, particularly ACC deaminase activity, could be under the observed in planta effects. Although the couple V. gossypii-MA11 reported a great benefit to plant growth and nodulation, the best result was observed in plants inoculated with the combination of the three bacteria. These results suggest that Variovorax strains could be used as biofertilizers to improve the adaptation of legumes to degraded soils in soil-recovery programs.

Impact of Plant Growth Promoting Bacteria on Salicornia ramosissima Ecophysiology and Heavy Metal Phytoremediation Capacity in Estuarine Soils.

Salicornia ramosissima is a C3 halophyte that grows naturally in South Western Spain salt marshes, under soil salinity and heavy metal pollution (mostly Cu, Zn, As, and Pb) caused by both natural and anthropogenic pressure. However, very few works have reported the phytoremediation potential of S. ramosissima. In this work, we studied a microbe-assisted phytoremediation strategy under greenhouse conditions. We inoculated plant growth promoting (PGP) and heavy metal resistant bacteria in pots with S. ramosissima and natural non-polluted and polluted sediments collected from Spanish estuaries. Then, we analyzed plant ecophysiological and metal phytoaccumulation response. Our data suggested that inoculation in polluted sediments improved S. ramosissima plant growth in terms of relative growth rate (RGR) (32%) and number of new branches (61%). S. ramosissima photosynthetic fitness was affected by heavy metal presence in soil, but bacteria inoculation improved the photochemical apparatus integrity and functionality, as reflected by increments in net photosynthetic rate (21%), functionality of PSII (F m and F v /F m ) and electron transport rate, according to OJIP derived parameters. Beneficial effect of bacteria in polluted sediments was also observed by augmentation of intrinsic water use efficiency (28%) and slightly water content (2%) in inoculated S. ramosissima. Finally, our results demonstrated that S. ramosissima was able to accumulate great concentrations of heavy metals, mostly at root level, up to 200 mg Kg-1 arsenic, 0.50 mg Kg-1 cadmium, 400 mg Kg-1 copper, 25 mg Kg-1 nickel, 300 mg Kg-1 lead, and 300 mg Kg-1 zinc. Bioaugmentation incremented S. ramosissima heavy metal phytoremediation potential due to plant biomass increment, which enabled a greater accumulation capacity. Thus, our results suggest the potential use of heavy metal resistant PGPB to ameliorate the capacity of S. ramosissima as candidate for phytoremediation of salty polluted ecosystems.

Uncovering PGPB Vibrio spartinae inoculation-triggered physiological mechanisms involved in the tolerance of Halimione portulacoides to NaCl excess.

Plant growth promoting bacteria' (PGPB) beneficial role on plant tolerance to salinity stress has previously been well recognized. However, bacteria-triggered plant physiological mechanisms involved in this response require investigation, especially in plants with innate salt tolerance. A glasshouse experiment was designed to investigate the effect of the PGPB Vibrio spartinae on Halimione portulacoides growth, physiological performance and ion homeostasis in plants exposed to 0, 171, 510 and 1020 mM NaCl for 100 days. Bacterial inoculation alleviated ~28% of the deleterious impact of salinity excess on the relative growth rate (RGR) in plants grown at 510 mM and led to 30% and 44% enhancements in those exposed to 0 and 171 mM NaCl, respectively. This effect was linked to a reduction in Na tissue concentrations which improved plant ion homeostasis at elevated NaCl concentration, and to the overall protective effects on various steps in the photosynthetic pathway between 0 and 510 mM NaCl. Thus, inoculated plants were able to maintain higher net photosynthesis (AN) than their non-inoculated counterparts. Hence, AN differences under saline conditions were ascribed to inoculation amelioration NaCl-induced CO2 diffusion limitations, as reflected in the greater gs and Ci values recorded at 171 and 510 mM NaCl, together with an enhancement of photochemical apparatus functionality (in terms of energy absorption, transformation and transport), as indicated by a higher electron transport rate (ETR) and energy fluxes derived from Kautsky curves, compared with their non-inoculated counterparts.

Pseudoalteromonas rhizosphaerae sp. nov., a novel plant growth-promoting bacterium with potential use in phytoremediation.

Strain RA15T was isolated from the rhizosphere of the halophyte plant Arthrocnemum macrostachyum growing in the Odiel marshes (Huelva, Spain). RA15T cells were Gram stain-negative, non-spore-forming, aerobic rods and formed cream-coloured, opaque, mucoid, viscous, convex, irregular colonies with an undulate margin. Optimal growth conditions were observed on tryptic soy agar (TSA) plates supplemented with 2.5 % NaCl (w/v) at pH 7.0 and 28 °C, although it was able to grow at 4-32 °C and at pH values of 5.0-9.0. The NaCl tolerance range was from 0 to 15 %. The major respiratory quinone was Q8 but Q9 was also present. The most abundant fatty acids were summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), C17 : 1 ω8c and C16 : 0. The polar lipids profile comprised phosphatidylglycerol and phosphatidylethanolamine as the most abundant representatives. Phylogenetic analyses confirmed the well-supported affiliation of strain RA15T within the genus Pseudoalteromonas, close to the type strains of Pseudoalteromonas neustonica, Pseudoalteromonas prydzensis and Pseudoalteromonas mariniglutinosa. Results of comparative phylogenetic and phenotypic studies between strain RA15T and its closest related species suggest that RA15T could be a new representative of the genus Pseudoalteromonas, for which the name Pseudoalteromonas rhizosphaerae sp. nov. is proposed. The type strain is RA15T (=CECT 9079T=LMG 29860T). The whole genome has 5.3 Mb and the G+C content is 40.4 mol%.

The ACC-Deaminase Producing Bacterium Variovorax sp. CT7.15 as a Tool for Improving Calicotome villosa Nodulation and Growth in Arid Regions of Tunisia.

Calicotome villosa is a spontaneous Mediterranean legume that can be a good candidate as pioneer plants to limit regression of vegetation cover and loss of biodiversity in Tunisian arid soils. In order to grow legumes in such soils, pairing rhizobia and nodule associated bacteria (NAB) might provide numerous advantages. In this work, cultivable biodiversity of rhizobial symbionts and NAB in nodules of C. villosa plants growing in five arid regions of south Tunisia was characterized. Phylogenetic analysis using 16S rDNA gene, dnak, recA and nodD sequences separated nodule-forming bacteria in six clades associated to genera Ensifer, Neorhizobium, Phyllobacterium and Rhizobium. Among NAB, the strain Variovorax sp. CT7.15 was selected due to its capacity to solubilise phosphate and, more interestingly, its high level of aminocyclopropane-1-carboxylate deaminase (ACC deaminase) activity. C. villosa plants were inoculated with representative rhizobia of each phylogenetic group and co-inoculated with the same rhizobia and strain CT7.15. Compared with single rhizobia inoculation, co-inoculation significantly improved plant growth and nodulation, ameliorated plant physiological state and increased nitrogen content in the plants, independently of the rhizobia used. These results support the benefits of pairing rhizobia and selected NAB to promote legume growth in arid or degraded soils.

Halomonas radicis sp. nov., isolated from Arthrocnemum macrostachyum growing in the Odiel marshes(Spain) and emended descriptions of Halomonas xinjiangensis and Halomonas zincidurans.

Strain EAR18T was isolated as an endophyte from the roots of a halophyte plant, Arthrocnemum macrostachyum, growing in the Odiel marshes (Huelva, Spain). Cells of strain EAR18T were Gram- stain-negative, motile, non-spore-forming aerobic rods. It grew optimally on tryptic soy agar supplemented with 2.5 % NaCl (w/v), at pH 7 and 30 °C for 48 h. It tolerated NaCl from 0 to 25 % (w/v). It presented Q9 as the major quinone and C19 : 0 cyclo ω8c, summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) and C16 : 0 as the predominant fatty acids. The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and four unidentified phospholipids. The results of phylogenetic analysis based on 16S rRNA gene sequences revealed that strain EAR18T formed a well-supported clade with species Halomonas zincidurans B6T and Halomonas xinjiangensis TRM 0175T (similarities of 98.3 and 96.1 % respectively). Furthermore, digital DNA-DNA hybridization analysis resulted in values of 20.4 % with H. xinjiangensis TRM 0175T and 35.50 % with H. zincidurans B6T, and ANIb/ANIm results in values of 73.8 %/84.2 % with H. xinjiangensis TRM 0175T and 86.8 %/89.4 % with H. zincidurans B6T. Based on phylogeny and differential phenotypic properties in comparison with its closest related species, strain EAR18T is suggested to represent a new species in the genus Halomonas, for which the name Halomonas radicis sp. nov. is proposed. The type strain is EAR18T (=CECT 9077T=LMG 29859T). The whole genome was sequenced, and it had a total length of 4.6 Mbp and a G+C content of 64.9 mol%.

Targeting Acr3 from Ensifer medicae to the plasma membrane or to the tonoplast of tobacco hairy roots allows arsenic extrusion or improved accumulation. Effect of acr3 expression on the root transcriptome.

Transgenic tobacco hairy roots expressing the bacterial arsenite efflux pump Acr3 from Ensifer medicae were generated. The gene product was targeted either to the plasma membrane (ACR3 lines) or to the tonoplast by fusing the ACR3 protein to the tonoplast integral protein TIP1.1 (TIP-ACR3 lines). Roots expressing Acr3 at the tonoplast showed greater biomass than those expressing Acr3 at the plasma membrane. Furthermore, higher contents of malondialdehyde (MDA) and RNA degradation in ACR3 lines were indicative of higher oxidative stress. The determination of ROS-scavenging enzymes depicted the transient role of peroxidases in ROS detoxification, followed by the action of superoxide dismutase during both short- and medium-term exposure periods. Regarding As accumulation, ACR3 lines accumulated up to 20-30% less As, whereas TIP-ACR3 achieved a 2-fold increase in As accumulation in comparison to control hairy roots. Strategies that presumably induce As uptake, such as phosphate deprivation or dehydration followed by rehydration in the presence of As, fostered As accumulation up to 10 800 µg g-1. Finally, the effects of the heterologous expression of acr3 on the root transcriptome were assessed. Expression at the plasma membrane induced drastic changes in gene expression, with outstanding overexpression of genes related to electron transport, ATP synthesis and ATPases, suggesting that As efflux is the main detoxification mechanism in these lines. In addition, genes encoding heat shock proteins and those related to proline synthesis and drought tolerance were activated. On the other hand, TIP-ACR3 lines showed a similar gene expression profile to that of control roots, with overexpression of the glutathione and phytochelatin synthesis pathways, together with secondary metabolism pathways as the most important resistance mechanisms in TIP-ACR3, for which As allocation into the vacuole allowed better growth and stress management. Our results suggest that modulation of As accumulation can be achieved by subcellular targeting of Acr3: expression at the tonoplast enhances As accumulation in roots, whereas expression at the plasma membrane could promote As efflux. Thus, both approaches open the possibilities for developing safer crops when grown on As-polluted paddy soils, but expression at the tonoplast leads to better growth and less stressed roots, since the high energy cost of As efflux likely compromises growth in ACR3 lines.