Improving Teaching Schemes in the Biology Degree to Learn how to Characterize Aquatic Ecosystems

En este capítulo se describe un Ciclo de Mejora en el Aula (CIMA) aplicado en la asignatura Ecología II del Grado en Biología de la Universidad de Sevilla. Concretamente, se lleva a cabo en clases prácticas donde los alumnos aprenden a caracterizar ecosistemas acuáticos. Se desarrolla en 3 sesiones, donde se toman muestras en el Parque del Alamillo y se analizan posteriormente en laboratorio. En el CIMA descrito, se trabajaron los tres aspectos fundamentales del Sistema Docente (Contenidos, Metodología y Evaluación), centrando la atención en el estudiante y su aprendizaje. Tras la experiencia, entre los principios didácticos que trataré de implementar en mi docencia se encuentran el trabajo en torno a problemas, la contextualización de los contenidos en un ámbito laboral, dar mayor cabida a las ideas de los alumnos, el empleo de actividades de contraste y, por último, adoptar una evaluación para mejorar el aprendizaje (y no solo del aprendizaje), del alumno, el método y el docente.This chapter describes a Classroom Improvement Cycle (CIMA) applied in Ecology II, in the Degree of Biology at the University of Seville. Specifically, it is developed in practical classes where the students learn to characterize aquatic ecosystems. In 3 sessions, samples are taken in Parque del Alamillo and subsequently analyzed in the laboratory. In the described CIMA, the three fundamental aspects of the Teaching System (Contents, Methodology and Evaluation) were addressed, focusing the attention on the student and his learning. After the experience, among the didactic principles that I will try to implement in my teaching are the work around problems, the contextualization of the contents in a work environment, giving more space to the ideas of the students, the use of contrast activities and, finally, adopt an assessment to improve learning and not just learning, the student, the method, and the teacher

Isolation of Plant Growth Promoting Rhizobacteria from Spartina densiflora and Sarcocornia perennis in San Antonio polluted salt marsh, Patagonian Argentina

With the purpose of Plant Growth Promoting Rhizobacteria (PGPR) isolation, several authors have sampled different wetlands in the northern half of Argentina. However, to date, we do not know the existence of microbiological studies conducted in the Patagonian salt marshes, and concretely, concerning isolation of PGPR. The present work was conducted in the heavy metal polluted San Antonio salt marsh, in two areas with different grade of pollution. In those areas, we isolated cultivable bacteria from the rhizosphere of the halophytes Spartina densiflora and Sarcocornia perennis, and look for several plant growth promoting (PGP) properties among them. In total, 60 different cultivable bacteria were isolated. 50% of the rhizobacterial strains demonstrated at least one of the PGP properties assayed, 25% of them produced siderophores, 16% were able to solubilize phosphate, 11% were able to produce auxins and 7% chitinase. We could observe that PGP properties were more abundant among bacteria growing in polluted soils. Also, bacteria inhabiting S. densiflora rhizosphere showed more PGP properties related to heavy metal phytostabilization mechanisms, in line with the phytoremediation strategy of this halophyte. Overall, these findings support the idea that coastal hazardous scenarios may be a good opportunity to seek for PGPR. Indeed, some of the strains isolated in this work presented more than one PGP property, so they may be selected for further formulation of inoculants for different applications. For further research, it would be interesting to analyse other PGP properties in these strains, as well as to isolate rhizobacteria from other halophytes in diverse Patagonian salt marshes.Fil: Idaszkin, Yanina Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; ArgentinaFil: Polifroni, Rosana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; ArgentinaFil: Mesa-Marín, Jennifer. Universidad de Sevilla; Españ

Effect of Plant Growth-Promoting Rhizobacteria on Salicornia ramosissima Seed Germination under Salinity, CO2 and Temperature Stress

In a scenario of climate change and growing population, halophyte root microbiota interactions may be a sustainable solution to improve alternative crop production while combating abiotic stress. In this work, seeds of the cash crop halophyte Salicornia ramosissima were inoculated with five different plant growth-promoting rhizobacteria consortia, isolated from the rhizosphere of five halophytes in southwestern Spain salt marshes. For the first time, we recorded seed germination response to three interactive abiotic stressors, CO2 (400 and 700 ppm), temperature (25 and 29 ℃) and salinity (171, 510 and 1030 mM NaCl), all of them related to climate change. Salinity played a decisive role, as no significant differences were registered between treatments at 171 mM NaCl and no germination took place at 1030 mM NaCl. At 510 mM NaCl, one rhizobacterial consortium improved seed parameters notably, increasing up to 114% germination percentage and 65% seedlings biomass. These first findings encourage us to think that cash crop halophytes like S. ramosissima and halophyte root microbiota may be valuable resources for human or animal feeding in a future climate reality.Ministerio de Economía y Competitividad (CGL2016-75550-R)Ministerio de Educación, Cultura y Deporte (FPU014/03987

Consortia of Plant-Growth-Promoting Rhizobacteria Isolated from Halophytes Improve the Response of Swiss Chard to Soil Salinization

Inadequate fertilization or the indiscriminate use of water with high salt concentrations have led to salinization of agricultural soils. In this context, biofertilization with plant-growth-promoting rhizobacteria (PGPR) is an environmentally benign strategy to stimulate plant growth, even under salt stress. Thus, we studied the use of isolated PGPR consortia from halophytes to enhance Swiss chard growth under saline conditions. Growth, photosynthetic apparatus response, nutrient status, pigment concentrations, and secondary metabolites with antioxidant activity were determined in Swiss chard plants grown at 0 and 85 mmol L−1 NaCl. In general, inoculation of plants with PGPR has been shown to be an effective strategy to stimulate the growth of Swiss chard and improve its tolerance to salt stress. Inoculated plants watered with 85 mmol L−1 NaCl showed higher values of leaf dry weight than control plants. Furthermore, PGPR inoculation reduced electrolyte leakage and Na+ uptake and improved chlorophyll a fluorescence parameters, chlorophyll and carotenoid concentrations, stomatal conductance, and antioxidant capacity of Swiss chard. Finally, our findings highlight the potential of isolated PGPR from halophytes to counterbalance the deleterious effect of salinity and stimulate crop growth.Junta de Andalucía DOC_0072

Salinity alleviates zinc toxicity in the saltmarsh zinc-accumulator Juncus acutus

The potential importance of Juncus acutus for remediation of Zn-contaminated lands has been recognized, because of its Zn tolerance and capacity to accumulate Zn. Since it is also a halophyte, the extent to which salinity influences its Zn tolerance requires investigation. A factorial greenhouse experiment was designed to assess the effect of NaCl supply (0 and 85 mM NaCl) on the growth, photosynthetic physiology and tissue ions concentrations of plants exposed to 0, 30 and 100 mM Zn. Our results indicated that NaCl supplementation alleviated the effects of Zn toxicity on growth, as Zn at 100 mM reduced relative growth rate (RGR) by 60% in the absence of NaCl but by only 34% in plants treated also with NaCl. This effect was linked to a reduction in Zn tissue concentrations, as well as to overall protective effects on various stages in the photosynthetic pathway. Thus, at 85 mM NaCl plants were able to maintain higher net photosynthesis (AN) than in the absence of added NaCl, although there were no differences in stomatal conductance (gs). This contributed to preserving the trade-off between CO2 acquisition and water loss, as indicated by higher intrinsic water use efficiency (iWUE). Hence, AN differences were ascribed to limitation in the RuBisCO carboxylation, manifested as higher intercellular CO2 concentration (Ci), together with dysfunction of PSII photochemistry (in term of light harvest and energy excess dissipation), as indicated by higher chronic photoinhibition percentages and variations in the photosynthetic pigment profiles in presence of Zn under non-saline conditions

Endophytic cultivable bacteria of the metal bioaccumulator Spartina maritima improve plant growth but not metal uptake in polluted marshes soils

Endophytic bacterial population was isolated from Spartina maritima tissues, a heavy metal bioaccumulator cordgrass growing in the estuaries of Tinto, Odiel, and Piedras River (south west Spain), one of the most polluted areas in the world. Strains were identified and ability to tolerate salt and heavy metals along with plant growth promoting and enzymatic properties were analyzed. A high proportion of these bacteria were resistant toward one or several heavy metals and metalloids including As, Cu, and Zn, the most abundant in plant tissues and soil. These strains also exhibited multiple enzymatic properties as amylase, cellulase, chitinase, protease and lipase, as well as plant growth promoting properties, including nitrogen fixation, phosphates solubilization, and production of indole-3-acetic acid (IAA), siderophores and 1-aminocyclopropane-1-carboxylate (ACC) deaminase. The best performing strains (Micrococcus yunnanensis SMJ12, Vibrio sagamiensis SMJ18, and Salinicola peritrichatus SMJ30) were selected and tested as a consortium by inoculating S. maritima wild plantlets in greenhouse conditions along with wild polluted soil. After 30 days, bacterial inoculation improved plant photosynthetic traits and favored intrinsic water use efficiency. However, far from stimulating plant metal uptake, endophytic inoculation lessened metal accumulation in above and belowground tissues. These results suggest that inoculation of S. maritima with indigenous metal-resistant endophytes could mean a useful approach in order to accelerate both adaption and growth of this indigenous cordgrass in polluted estuaries in restorative operations, but may not be suitable for rhizoaccumulation purposes

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 (Fm and Fv/Fm) 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.Ministerio de Economía y Competitividad (CGL2016-75550-R, AEI/FEDER, UE

Potencial biotecnológico de spartina maritima e inoculantes bacterianos para la recuperación de estuarios andaluces contaminados con metales pesados

Heavy metal pollution is a growing environmental problem with a major detrimental impact on ecosystems and living organisms’ health. The joint estuary of the Tinto and Odiel rivers in Huelva (Spain) is known as one of the most polluted areas by heavy metals in the world. Phytoremediation strategies have been proposed as a cheaper and eco-friendly alternative to physicochemical remediation procedures. In this context, halophyte cordgrasses in the genus Spartina come under the spotlight due to their heavy metal bioaccumulation capacity. In occidental Andalusian salt marshes, S. maritima and S. densiflora grow naturally. Nonetheless, S. densiflora is an invasive species that is gradually affecting coasts, flora and fauna dynamics. Accordingly, in this Doctoral Thesis the use of autochthonous plant growth promoting bacteria is proposed to enhance the phytoremediation potential of native S. maritima as a biotool to rehabilitate degraded salt marshes. Soil heavy metal concentration in Tinto and Odiel estuaries was determined to outreach the threshold intervention values settled by state laws. These high pollution levels dictated soil microbial dynamics in estuarine soils over S. maritima rhizosphere or seasonal changes. Cultivable bacteria were isolated from S. maritima rhizosphere and inner tissues and, based on their plant growth promoting properties and multiresistance to heavy metals, two bacterial consortia (rhizospheric and endophytic) with potential use to facilitate phytoremediation were designed. Under greenhouse conditions, bioaugmentation treatments with both consortia improved S. maritima growth and physiological parameters. However, whereas endophytic inoculation lessened metal accumulation in above and belowground tissues, bioaugmentation with rhizobacteria stimulated S. maritima root metal uptake. On the whole, this thesis supports that bioaugmentation treatments with autochthonous bacteria may be claimed as a biotool to enhance native S. maritima adaptation and metal rhizoaccumulation in Andalusian salt marshes.La contaminación por metales pesados es un creciente problema ambiental con un importante impacto negativo en los ecosistemas y la salud. El estuario conjunto de los ríos Tinto y Odiel en Huelva (España) es conocido como una de las zonas más contaminadas por metales pesados del mundo. La fitorremediación se ha propuesto como una alternativa más económica y respetuosa con el medio ambiente que los procedimientos de remediación físico-químicos tradicionales. En este contexto, las gramíneas halófitas del género Spartina cobran protagonismo debido a su capacidad de bioacumulación de metales pesados. En las marismas occidentales de Andalucía, S. maritima y S. densiflora crecen de forma natural. No obstante, S. densiflora es una especie invasora que está afectando gradualmente a la dinámica de costas, flora y fauna. Así, en esta Tesis Doctoral se propone el empleo de bacterias autóctonas promotoras del crecimiento vegetal para mejorar el potencial fitorremediador de la especie nativa S. maritima como bioherramienta para la recuperación de las marismas degradadas. La concentración en suelo de metales pesados determinada en los estuarios sobrepasó los valores de intervención límite establecidos por la legislación estatal. Estos elevados niveles de contaminación dictaron la dinámica de las poblaciones microbianas de los suelos marismeños, por encima de la presencia de S. maritima o los cambios estacionales. Se aislaron bacterias cultivables de la rizosfera y el interior de los tejidos de S. maritima y, en base a sus propiedades promotoras del crecimiento vegetal y multirresistencia a metales pesados, se diseñaron dos consorcios bacterianos (rizosférico y endofítico) con potencial empleo para la mejora de la fitorremediación. En condiciones de invernadero, la bioaumentación con ambos consorcios mejoró el crecimiento y los parámetros fisiológicos de S. maritima. Sin embargo, mientras que la inoculación con endofitos disminuyó la fitoacumulación de metales en tejidos aéreos y radiculares, la bioaumentación con rizobacterias estimuló la rizoacumulación de metales en S. maritima. En resumen, esta tesis sostiene que los tratamientos de bioaumentación con bacterias autóctonas en la nativa S. maritima podrían suponer una bioherramienta para mejorar su adaptación y capacidad de acumulación de metales pesados en las marismas andaluzas.Premio Extraordinario de Doctorado U

Synergistic Effect of Plant-Growth-Promoting Rhizobacteria Improves Strawberry Growth and Flowering with Soil Salinization and Increased Atmospheric CO2 Levels and Temperature Conditions

Biofertilization with plant-growth-promoting rhizobacteria (PGPR) can positively affect the growth and health of host plants and reinforce their tolerance of stressors. Here, we investigate the use of isolated PGPR consortia from halophytes to improve strawberry growth and flowering performance under saline and elevated CO2 and temperature conditions. Growth, flower bud production, and the photosynthetic apparatus response were determined in strawberry plants grown at 0 and 85 mmol L−1 NaCl and in two atmospheric CO2-temperature combinations (400/700 ppm and 25/+4 °C, respectively). Biofertilization improved strawberry plant growth and flower bud production, independently of salinity conditions, at ambient CO2 and 25 °C, while bacterial inoculation only had a positive effect on plant growth in the presence of salt in high CO2 and at +4 °C. Biofertilizers 1 and 3 generated the largest biomass of strawberries at 400 ppm CO2 and 0 and 85 mmol L−1 NaCl, respectively, while biofertilizer 1 did so in the presence of salt and in an atmosphere enriched with CO2 and at +4 °C. The effect of the consortia was mediated by bacterial strain PGP properties, rather than by an improvement in the photosynthetic rate of the plants. Furthermore, biofertilizers 1 and 2 increased the number of flower buds in the absence of salt, while biofertilizers 3 and 4 did so for salt-inoculated plants at 400 ppm CO2 and at 25 °C. There was no effect of inoculation on flower bud production of plants grown at high CO2 and at +4 °C. Finally, we concluded that the effect of bacterial inoculation on strawberry growth and flowering depended on the type of bacterial strain and growth conditions. This highlights the importance of developing studies considering stress interaction to assess the real potential of biofertilizers

Synergistic Effect of Plant-Growth-Promoting Rhizobacteria Improves Strawberry Growth and Flowering with Soil Salinization and Increased Atmospheric CO2 Levels and Temperature Conditions

Biofertilization with plant-growth-promoting rhizobacteria (PGPR) can positively affect the growth and health of host plants and reinforce their tolerance of stressors. Here, we investigate the use of isolated PGPR consortia from halophytes to improve strawberry growth and flowering performance under saline and elevated CO2 and temperature conditions. Growth, flower bud production, and the photosynthetic apparatus response were determined in strawberry plants grown at 0 and 85 mmol L−1 NaCl and in two atmospheric CO2-temperature combinations (400/700 ppm and 25/+4 °C, respectively). Biofertilization improved strawberry plant growth and flower bud production, independently of salinity conditions, at ambient CO2 and 25 °C, while bacterial inoculation only had a positive effect on plant growth in the presence of salt in high CO2 and at +4 °C. Biofertilizers 1 and 3 generated the largest biomass of strawberries at 400 ppm CO2 and 0 and 85 mmol L−1 NaCl, respectively, while biofertilizer 1 did so in the presence of salt and in an atmosphere enriched with CO2 and at +4 °C. The effect of the consortia was mediated by bacterial strain PGP properties, rather than by an improvement in the photosynthetic rate of the plants. Furthermore, biofertilizers 1 and 2 increased the number of flower buds in the absence of salt, while biofertilizers 3 and 4 did so for salt-inoculated plants at 400 ppm CO2 and at 25 °C. There was no effect of inoculation on flower bud production of plants grown at high CO2 and at +4 °C. Finally, we concluded that the effect of bacterial inoculation on strawberry growth and flowering depended on the type of bacterial strain and growth conditions. This highlights the importance of developing studies considering stress interaction to assess the real potential of biofertilizers.Ministerio de Ciencia e Innovación PDC2021-120951-I00Junta de Andalucía Talento Doctores DOC_0072