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Isolation, characterization and identification of bacteria associated with Opuntia spp. and its effect on the germination and growth of Arabidopsis thaliana L.
No full text"Las interacciones microorganismo-planta son muy importantes para las plantas ya que algunas bacterias conocidas como promotoras del crecimiento vegetal (PGPB, por sus siglas en inglés) tienen la capacidad de promover su crecimiento a través de la fijación de N2, la solubilización de fósforo, la producción de fitohormonas, compuestos orgánicos volátiles (COVs), por sideróforos, entre otros mecanismos, que pueden ocurrir tanto en la endósfera como en la rizósfera de la planta. Se ha encontrado que las PGPB son muy importantes para el establecimiento de algunas cactáceas en zonas áridas y semiáridas de México, sin embargo, aún son escasos este tipo de estudios para especies de esta familia, en específico para Opuntia. Por lo tanto, se plantearon dos objetivos: 1) aplicar ácido giberélico (GA3) y ácido indolacético (AIA) a las semillas de Opuntia streptacantha, O. leucotricha y O. robusta para probar si era posible romper su latencia fisiológica, además, se experimentó con semillas desinfectadas y no desinfectadas superficialmente para comprobar el efecto de la microbiota de la testa en su germinación; 2) aislar y caracterizar PGPB de la endósfera de semillas y rizósfera de las tres especies de Opuntia con capacidad para producir AIA, COVs y sideróforos, y probar su efecto en la germinación y el crecimiento de la planta modelo Arabidopsis thaliana L. Las fitohormonas no promovieron la germinación de las tres especies de Opuntia, pero si se observó un efecto negativo de la desinfección de las semillas en su germinación, lo que sugiere que su microbiota juega un papel muy importante en la germinación de las mismas. Se aislaron 108 cepas bacterianas de la rizósfera y 14 cepas de la endósfera de las semillas, de las cuales se identificaron siete cepas como las mayores productoras de AIA (de entre 23 y 175 μg/ mL de cultivo O.D. 0.4560nm) pertenecientes a los géneros: Micrococcus, Ensifer (Sinorhizobium), Variovorax, Endobacter (Gluconacetobacter) y Kocuria, las cuales se inocularon junto con A. thaliana L. para evaluar su crecimiento. Endobacter (Gluconacetobacter) promovió 80% más el crecimiento de la longitud total de A. thaliana comparado con el testigo, posiblemente por el efecto de COVs, y Ensifer (Sinorhizobium sp.) promovió 30% más el crecimiento de la longitud total de A. thaliana, posiblemente por el efecto del AIA, proponiéndose estas dos cepas como PGPB de A. thaliana y probablemente de Opuntia spp. En conclusión, se aislaron géneros bacterianos, anteriormente no reportados para cactáceas, con la capacidad de producir AIA, COVs y sideróforos, y se comprobó su efecto en la promoción del crecimiento de A. thaliana L.""The microorganism-plant interactions are very important for plants, some bacteria
known as plant growth promoters (PGPB) have the ability to promote their growth
through the fixation of N2, the phosphorus solubilization , phytohormones, volatile
organic compounds (VOCs) and siderophores production, among other
mechanisms, which can occur both in the endosphere and in the rhizosphere of the
plant. It has been found that PGPB are very important for the establishment of
some cacti in arid and semiarid zones of Mexico, however, this type of studies is
still scarce for species of this family, specifically for Opuntia. Therefore, two
objectives were proposed: 1) apply gibberellic acid (GA3) and indoleacetic acid
(IAA) to the seeds of Opuntia streptacantha, O. leucotricha and O. robusta to test if
it was possible to break their physiological latency, also, experimented with seeds
disinfected and not disinfected superficially to check the effect of the microbiota of
the seed coat on its germination; 2) isolate and characterize PGPB from the seed
endosphere and rhizosphere of the three Opuntia species with the capacity to
produce IAA, VOCs and siderophores, and test their effect on the germination and
growth of the model plant Arabidopsis thaliana L. Phytohormones did not promote
the germination of the three Opuntia species, but a negative effect of the
disinfection of the seeds was observed in their germination, which suggests that
their microbiota plays a very important role in their germination. We isolated 108
bacterial strains from the rhizosphere and 14 strains of the seed endosphere, of
which seven strains were identified as the major producers of AIA (between 23 and
175 μg/ mL of culture OD 0.4560nm) belonging to the genera: Micrococcus, Ensifer
(Sinorhizobium), Variovorax, Endobacter (Gluconacetobacter) and Kocuria, which
were inoculated in A. thaliana L. to evaluate their growth. Endobacter
(Gluconacetobacter) promoted 80% more total length growth of A. thaliana
compared to the control, possibly due to the effect of VOCs, and Ensifer
(Sinorhizobium sp.) promoted 30% more the growth of the total length of A.
thaliana, possibly due to the effect of AIA. These two strains are proposed as
PGPB of A. thaliana and probably of Opuntia spp. In conclusion, bacterial genera,
previously not reported for cacti, were isolated with the ability to produce AIA,
VOCs and siderophores, and their effect on the growth promotion of A. thaliana L
was tested.
Synthesis and magnetocaloric characterization of rapidly solidified ErMn2 melt-spun ribbons
Get PDF"We have fabricated melt-spun ribbons of nominal composition ErMn2 and studied their phase constitution and magnetocaloric (MC) properties by X-ray diffraction, scanning electron microscopy (SEM), magnetization and heat capacity measurements. The major phase formed shows the MgZn2-type hexagonal structure (C14-type); however, both XRD and SEM analyses revealed the formation of impurity phases (i.e., Er6Mn23 and ErMn12). Ribbons exhibit a saturation magnetization of 149 Am2kg?1 at 2 K and a Curie temperature of TC = 15 K. A field-induced metamagnetic transition at very low critical magnetic fields was observed below 8 K that leads to a change of sign in the magnetic entropy change ?SM below this temperature (?SMpeak = 2.5 Jkg?1K?1 at 2 K and 5 T). For a magnetic field change of 5 T (2 T) applied along the ribbon length, the samples show a large peak value of the magnetic entropy change ?SMpeak of ?20.5 (?10.8) Jkg?1K?1, a full-width at half-maximum ?TFWHM for the ?SM(T) curve of 20 (12) K, and a maximum adiabatic temperature change ?Tadmax of 7.4 (3.6) K. The obtained results are compared with the reported in literature by other authors for bulk alloys.
Study of the presence of spherical deformations on the Al top electrode due to electroforming in rewritable organic resistive memories
No full text"Physical deformations are observed at the top electrodes during the electroforming process in Al/PEDOT: PSS + nitrogen doped multiwalled carbon nanotube (N-MWCNTs)/Al rewritable resistive memory devices. These physical deformations arise from electrochemical reactions, i. e., a reduction reaction in the native Al oxide layer, which are similar to those reported in TiO2-based resistive memory devices. These memory devices are electroformed at the ON state using an similar to -2 V pulse or at the OFF state using an similar to 3 V pulse. These processes are current-controlled; a minimum compliance current is necessary to obtain the electroforming of the device, generally between 5 to 10 mA. SEM and AFM micrographs show the presence of spherical deformations at the top electrode due to O-2 gas formation generated by the reduction in the native AlOx layer during the electroformation, with a diameter of similar to 7 micrometres for positive voltage or a smaller diameter of similar to 3 micrometres for negative voltage. After top-electrode delamination, circular craters are found in the active layer in the vicinity of the N-MWCNTs, which only occurs when a negative voltage is used in the electroformation, indicating that film damage is induced by oxygen bubbles created at the bottom electrode/polymeric film interface.
Aboveground biomass of Vochysia guatemalensis in a rain tropical forest of the Chinantla, Oaxaca
Get PDF"Se estimó la biomasa aérea de Vochysia guatemalensis Donn. Smith., una especie de importancia ecológica y económica en el sur-sureste de México. Se derribaron siete árboles de cuatro categorías diamétricas (10, 15, 20 y 25 cm), para luego separarlos por componente estructural. De cada componente se obtuvieron muestras que se pesaron en fresco y se secaron en estufa. Con estos datos se estableció el peso seco para estimar la biomasa por componente y árbol total en cada categoría, ajustando ecuaciones alométricas mediante técnicas de regresión no lineal. Los valores de biomasa aérea por árbol uctuaron de 8.264 a 105.099 kg en fustes, de 0.329 a 21.442 kg en ramas y de 0.393 a 9.609 kg en follaje. A nivel de árbol 79.68 % de la biomasa se encontró en fustes, 13.58 % en ramas y 6.72 % en follaje. ""The aboveground biomass of Vochysia guatemalensis Donn. Smith., a species of ecological and economic importance in the south-southeast of Mexico, was estimated. Seven trees of four diameter categories (10, 15, 20 and 25 cm) were felled and then separated by structural component. Samples were obtained from each component, weighed fresh and then oven dried. To determine the dry weight and estimate the biomass per component and total tree in each category, allometric equations were fitted using nonlinear regression techniques. The values of aboveground biomass per tree ranged from 8,264 to 105,099 kg in stems, from 0.329 to 21.442 kg in branches and from 0.393 to 9.609 kg in foliage. At tree level 79.68% of the biomass was found in stems, 13.58% in branches and 6.72% in foliage.
Comparison of two synthesis methods on the preparation of Fe, N-Co-doped TiO2 materials for degradation of pharmaceutical compounds under visible light
Get PDF"In this work, we report the synthesis, characterization and photocatalytic evaluation of visible light active iron-nitrogen co-doped titanium dioxide (Fe3+-TiO2?xNx) nanostructured catalyst. Fe3+-TiO2?xNx was synthesized using two different chemical approaches: sol-gel (SG) and microwave (MW) methods. The materials were fully characterized using several techniques (SEM, UV–Vis diffuse reflectance DRS, X-ray diffraction XRD, and X-ray photoelectron spectroscopy XPS). The photocatalytic activity of the nanostructured materials synthesized by both methods was evaluated for the degradation of amoxicillin (AMX), streptomycin (STR) and diclofenac (DCF) in aqueous solution. Higher degradation efficiencies were encountered for the materials synthesized by the SG method, for instance, degradation efficiencies values of 58.61% (SG) and 46.12% (MW) were observed for AMX after 240 min of photocatalytic treatment under visible light at pH 3.5. With STR the following results removal efficiencies were obtained: 49.67% (SG) and 39.90% (MW) at pH 8. It was observed the increasing of degradation efficiencies values at longer treatment periods, i.e., after 300 min of photocatalytic treatment under visible light, AMX had a degradation efficiency value of 69.15% (MW) at pH 3.5, DCF 72.3% (MW) at pH 5, and STR 58.49% (MW) at pH 8.
Consumption of Amaranth Induces the Accumulation of the Antioxidant Protein Paraoxonase/Arylesterase 1 and Modulates Dipeptidyl Peptidase IV Activity in Plasma of Streptozotocin-Induced Hyperglycemic Rats
No full text"Scope: Amaranth grain is a source of several bioactive compounds such as cancer-preventive and ACE inhibitory peptides. In vitro analysis of amaranth proteins has also demonstrated the presence of bioactive peptides, which exert inhibitory activity upon dipeptidyl peptidase IV (DPPIV), a new target for type 2 diabetes, but this potential activity has not been tested in vivo. The aim of this work was to evaluate whether chronic amaranth consumption has a beneficial effect in streptozotocin-induced diabetic rats, particularly in DPPIV activity and changes in plasma proteome profile. Methods and results: Diabetic rats were fed with 20% popped amaranth grain diet for 12 weeks. Changes in lipid profile, DPPIV activity in plasma and kidney, as well changes in plasma proteome were evaluated. Total cholesterol and DPPIV activity in plasma were increased in diabetic rats but this was ameliorated by amaranth consumption. Diabetic rats fed with amaranth showed the highest levels of HDL and this correlated with an accumulation of apolipoprotein (apo) A-II. Furthermore, amaranth diet stimulated the up-accumulation of the antioxidant protein paraoxonase 1(PON1). Conclusion This study provides molecular evidence about the role of amaranth as a potential functional food with DPPIV inhibitory activity and with a positive effect in plasma lipoproteins.
Observer-less output-feedback global continuous control for the finite-time and exponential stabilization of mechanical systems with constrained inputs
Get PDF"An observer-less output-feedback global continuous control scheme for the finite-time or (local) exponential stabilization of mechanical systems with constrained inputs is proposed. The approach is formally developed within the theoretical framework of local homogeneity. The closed-loop analysis incorporates a complementary insight on the control-induced motion dissipation through an ad hoc feedback-system passivity theorem. The work includes a simulation implementation section where the performance difference of the proposed scheme with previous observer-based and differentiation algorithms is brought to the fore.
Estabilidad de sistemas por medio de polinomios Hurwitz
Get PDF"Para analizar la estabilidad de un sistema de ecuaciones diferenciales lineales x=Axpodemos estudiar la localización de las raíces del polinomio característico pA(t) asociado a la matriz A. En este artículo presentamos diversos criterios algebraicos y geométricos que nos ayudan a determinar el lugar donde se encuentran las raíces sin necesidad de calcularlas en forma directa.
Environmental growth conditions of Trichoderma spp. affects indole acetic acid derivatives, volatile organic compounds, and plant growth promotion
Get PDF"Trichoderma species are soil-borne filamentous fungi widely utilized for their many plant health benefits, such as conferring improved growth, disease resistance and abiotic stress tolerance to their hosts. Many Trichoderma species are able to produce the auxin phytohormone indole-3-acetic acid (IAA), and its production has been suggested to promote root growth. Here we show that the production of IAA is strain dependent and diverse external stimuli are associated with its production. In in vitro assays, Arabidopsis primary root length was negatively affected by the interaction with some Trichoderma strains. In soil experiments, a continuum effect on plant growth was shown and this was also strain dependent. In plate assays, some strains of Trichoderma spp. inhibited the expression of the auxin reporter gene DR5 in Arabidopsis primary roots but not secondary roots. When Trichoderma spp. and A. thaliana were physically separated, enhancement of both shoot and root biomass, increased root production and chlorophyll content were observed, which strongly suggested that volatile production by the fungus influenced the parameters analyzed. Trichoderma strains T. virens Gv29.8, T. atroviride IMI206040, T. sp. "atroviride B" LU132, and T. asperellum LU1370 were demonstrated to promote plant growth through volatile production. However, contrasting differences were observed with LU1370 which had a negative effect on plant growth in soil but a positive effect in plate assays. Altogether our results suggest that the mechanisms and molecules involved in plant growth promotion by Trichoderma spp. are multivariable and are affected by the environmental conditions.
Iron-modified carbon paste electrodes and their application as sensors in As(V) detection
Get PDF"La detección electroquímica de arsénico(V) fue evaluada en un electrodo de pasta de carbón modificado con partículas de hidro(óxidos) de hierro en medio electrolítico de NaNO3. El polvo de grafito modificado se preparó fácilmente utilizando el método “slurry”. El material resultante fue caracterizado mediante la determinación de su distribución de carga superficial y punto de carga cero, distribución de pKa’s de los grupos funcionales superficiales, área superficial y distribución de tamaño del poro mediante la ecuación de Brunauer- Emmett-Teller (BET) y la identificación de las formas cristalinas de los compuestos de hidro(óxidos) de hierro por difracción de rayos X. Adicionalmente, se encontró que el material modificado exhibió una buena capacidad de remoción de As(V), incluso en el medio electrolítico. Para la detección de As(V), se utilizó la técnica de voltamperometría de pulso diferencial, para la cual se aplicó un potencial de reducción/acumulación de -1.10 V(vs. Ag/AgCl/KCl (sat.) por 180 segundos a pH 2.5. La caracterización fisicoquímica de los materiales modificados y el análisis electroquímico, permitió proponer un mecanismo de reducción de As(V) sobre la superficie del electrodo. El límite de detección (LOD) de As(V) alcanzado fue de 19.40 ?g/L, por lo cual este electrodo podría ser potencialmente aplicado como sensor en la detección de este contaminante en muestras de agua.""The electrochemical detection of arsenic (V) [As(V)] was evaluated on a carbon paste electrode modified with iron hydro(oxide) particles in the presence of NaNO3 salt used as electrolytic media in the experiments. The modified graphite powder was easily prepared using the slurry method. The resulting material was examined by surface charge and pKa´s distribution, point of zero charge, Brunauer-Emmett-Teller (BET) surface area and pore size distribution, potentiometric titration and X-ray diffraction. Adsorption experiments with the modified materials exhibited good As(V) removal capacity even in the presence of electrolytic media. For the As(V) detection, differential pulse voltammetry technique was used by the application of reduction potential of -1.10 V for 180 s at pH 2.5. The detailed physicochemical characterization of modified materials and electrochemical analysis allowed to propose a reduction mechanism of As(V) on the electrode surface. Detection limit of 10 ?g/L can be achieved for As(V), therefore this electrode could potentially be applied as a sensor for the detection of this pollutant in water samples.