Fijación biológica del nitrógeno: factores limitantes

8 páginas y 2 tablasLa Fijación Biológica de Nitrógeno (FBN) representa una alternativa a la fertilización nitrogenada ya que puede paliar muchos de los efectos negativos que dicha fertilización produce tanto a nivel sanitario. La FBN está relegada a organismos procariontes que son capaces de reducir el nitrógeno molecular a amoniaco tanto en vida libre como en simbiosis. La mayor parte del nitrógeno fijado en los ecosistemas terrestres se realiza mediante la asociación simbiótica de bacterias de los géneros Rhizobium, Bradyrhizobium, Sinorhizobium, Azorhizobium y Mesorhizobium (Rhizobium para generalizar) con plantas leguminosas. Gran parte de estas asociaciones simbióticas tiene interés para la Agricultura. Sin embargo, aunque los rendimientos de la FBN se han incrementado considerablemente en los últimos años, al trasladar estos conocimientos a la Agricultura práctica, se detectan limitaciones a la fijación biológica en la simbiosis a nivel medioambiental, biológico, metodológico y a nivel de producción. En este trabajo se analiza el efecto de alguno de estos factores sobre la fijación de nitrógeno y la producción final de grano, desde el punto de vista fisiológico, bioquímico y estructural en la simbiosis Rhizobium-leguminosa.CSIC - Centro de Ciencias Medioambientales (CCMA)Peer reviewe

Colonisatoin of Pinus halepensis roots by Pseudomonas fluorescens and interaction with the ectomycorrhizal fungus Suillus granulatus

8 pages, figures, and tables statistics.Colonisation of Pinus halepensis roots by GFP-tagged Pseudomonas fluorescens Aur6 was monitored by epifluorescence microscopy and dilution plating. Aur6-GFP was able to colonise and proliferate on P. halepensis roots. Co-inoculation with the ectomycorrhizal fungus Suillus granulatus did not affect the bacterial colonisation pattern whereas it had an effect on bacterial density. Bacterial counts increased during the first 20 days of seedling growth, irrespective of seedlings being mycorrhizal or not. After 40 days, bacterial density significantly decreased and bacteria concentrated on the upper two-thirds of the pine root. The presence of S. granulatus significantly stimulated survival of bacteria in the root elongation zone where fungal colonisation was higher. The number of mycorrhizas formed by S. granulatus was not affected by co-inoculation with Aur6-GFP. Neither Aur6-GFP nor S. granulatus stimulated P. halepensis development when inoculated alone, but a synergistic effect was observed on seedling growth when bacteria and fungus were co-inoculated.Peer reviewe

Early mobilisation in critically ill COVID-19 patients: a subanalysis of the ESICM-initiated UNITE-COVID observational study

Background Early mobilisation (EM) is an intervention that may improve the outcome of critically ill patients. There is limited data on EM in COVID-19 patients and its use during the first pandemic wave. Methods This is a pre-planned subanalysis of the ESICM UNITE-COVID, an international multicenter observational study involving critically ill COVID-19 patients in the ICU between February 15th and May 15th, 2020. We analysed variables associated with the initiation of EM (within 72 h of ICU admission) and explored the impact of EM on mortality, ICU and hospital length of stay, as well as discharge location. Statistical analyses were done using (generalised) linear mixed-effect models and ANOVAs. Results Mobilisation data from 4190 patients from 280 ICUs in 45 countries were analysed. 1114 (26.6%) of these patients received mobilisation within 72 h after ICU admission; 3076 (73.4%) did not. In our analysis of factors associated with EM, mechanical ventilation at admission (OR 0.29; 95% CI 0.25, 0.35; p = 0.001), higher age (OR 0.99; 95% CI 0.98, 1.00; p ≤ 0.001), pre-existing asthma (OR 0.84; 95% CI 0.73, 0.98; p = 0.028), and pre-existing kidney disease (OR 0.84; 95% CI 0.71, 0.99; p = 0.036) were negatively associated with the initiation of EM. EM was associated with a higher chance of being discharged home (OR 1.31; 95% CI 1.08, 1.58; p = 0.007) but was not associated with length of stay in ICU (adj. difference 0.91 days; 95% CI − 0.47, 1.37, p = 0.34) and hospital (adj. difference 1.4 days; 95% CI − 0.62, 2.35, p = 0.24) or mortality (OR 0.88; 95% CI 0.7, 1.09, p = 0.24) when adjusted for covariates. Conclusions Our findings demonstrate that a quarter of COVID-19 patients received EM. There was no association found between EM in COVID-19 patients' ICU and hospital length of stay or mortality. However, EM in COVID-19 patients was associated with increased odds of being discharged home rather than to a care facility. Trial registration ClinicalTrials.gov: NCT04836065 (retrospectively registered April 8th 2021)

El ozono en la Salud

8 páginas[EN]The present review enhances the major importance of the ozone, both by protecting the life in the Earth, and also by its medicinal interest, due to the beneficial effect in the treatment of several diseases. The ozone protects the human health from the environment contamination and also helps to get over of several human diseases. The ozone layer (stratospheric ozone) is as a thin shield, surrounding the Earth and protecting it against the dangerous sun rays. The ozone is the only substance in the atmosphere being able to absorb the dangerous ultraviolet radiation (UV-B) from the sun. [ES]La presente revisión alude al importante papel del ozono estratosférico en la protección del entorno externo e interno del ser humano. Se analiza el efecto protector del ozono sobre el entorno medioambiental del hombre, protegiendo la vida de los seres vivos, y también, se analiza su protagonismo en la salud humana, como agente terapéutico capaz de recuperar dolencias. El ozono protege ambientalmente al hombre y le ayuda a combatir la enfermedad. El ozono es una forma alotrópica del oxígeno, que participa en el equilibrio ecológico de la Tierra. Entre los 19 y los 23 Km sobre la superficie terrestre, en la estratosfera, un delgado escudo de gas (capa de ozono), rodea la Tierra y la protege de todas las dañinas radiaciones ultravioleta del sol (UV-B). La disminución del escudo de ozono sobre la superficie terrestre, observada en las mediciones de los parámetros ambientales, se traduce en un aumento de los niveles de radiación ultravioleta-B. Esta radiación daña a los seres humanos, animales y plantas. Actualmente, se está constatando un aumento del cáncer de piel, el denominado melanoma, y cambios en la composición de los constituyentes de las plantas, disminución de las cosechas y perjuicios en la masa forestal.Peer reviewe

Biotecnologías limpias en agricultura: Fijación Biológica de nitrógeno. Estructura-función de la simbiosis Rhizobium-Leguminosa

La agricultura intensiva ha llevado a la contaminación de suelos y aguas, debido al abuso de fertilizantes y fitosanitarios para obtener grandes producciones. Como alternativas a la agricultura intensiva, las biotecnologías limpias, basadas en el uso de los microorganismos del suelo como activadores del crecimiento, están adquiriendo especial relieve por ser respetuosas con el Medio Ambiente. Desde 1985 nuestro grupo de investigación viene trabajando en Fijación biológica de nitrógeno con plantas leguminosas, que tienen gran importancia agronómica, son base de la dieta mediterránea y tienen características propias y exclusivas, como fijar nitrógeno en sus raíces. Esta propiedad, unido a que además sus raíces ayudan a la reconstrucción de suelos degradados por diferentes estreses, hace que las leguminosas puedan ser utilizadas para mejorar las características físico-químicas y nutricionales de zonas áridas y semiáridas.Peer reviewe

Interacciones microoganismos-suelo-planta en la preservación del Medio Ambiente y la salud

Se pone de relieve la importancia de los microorganismos del suelo, que establecen simbiosis con las plantas como biofertilizantes y su aplicación en el control biológico de patógenos. Las interacciones beneficiosas: bacteria-planta y hongo-planta tienen gran interés por su impacto en la Agricultura, Silvicultura y Medioambiente y constituyen una alternativa a la aplicación de fertilizantes químicos que actúan como contaminantes de suelos y aguas con gran perjuicio para la salud. Las bacterias fijadoras de nitrógeno y los hongos micorrizógenos se encuentran entre los simbiontes de plantas más extendidos y ecológicamente más importantes. El potencial de los microorganismos del suelo parece ilimitado. Corresponde a la ciencia realizar el estudio profundo de las interacciones de organismos autóctonos del suelo con las plantas, con el fin de que éstas puedan autoabastescerse y autodefenderse en condiciones ambientales adversas, y además se cumpla con el deber de mantener nuestro planeta en óptimas condiciones de salud ambiental para las generaciones futuras

Effects of different O2 concentrations on nitrogenase activity, respiration, and O2 diffusion resistance in Lupinus albus L. cv. Multolupa nodules

8 pages, figures, and tables statistics.Nitrogenase, responsible for N2 fixation in legume nodules, can be denatured by O2 and functions under microaerobic conditions. However, O2 is required for ATP production associated with nitrogenase activity; therefore, O2 concentration within infected cells is highly regulated by a combination of nodule respiration, leghaemoglobin, and an O2 diffusion barrier. To investigate O2 diffusion regulation, different concentrations (1%, 21%, and 40% (v/v)) were applied to nodulated root systems of Lupinus albus for 3 and 10 days. The application of 1% O2 for 3 days produced a marked decrease in nitrogenase activity, up to 30% of that of control (21% O2) plants. The irreversible failure of nitrogenase functioning occurred after 10 days and could not be explained by the small variations in the content of nitrogenase components I and II. The internal O2 concentration seems to be a limiting factor to N2 fixation, but nodules can partly maintain their activity if hypoxic conditions are not too prolonged. The nitrogenase inhibition of the 3-day 40% O2 treatment was moderate (<20 %), and after 10 days nitrogenase activity returned to control values. Again, variations in nitrogenase components were not correlated with the activity measured by acetylene reduction in a flow-through system. Root respiration rates were unexpectedly reduced. These plants seemed to adapt to 40% O2 by varying the minimum resistance (Rmin) of the O2 diffusion barrier, which was almost doubled from the third day of treatment.The authors are very grateful to Dr. F. Minchin (IGER, U.K.) for the revision of the manuscript. They also thank C. de Mesa, L. Melendo, I. Menendez, and F. Pinto for their technical assistance, and Dr. Pueyo for comments on the first version of this manuscript. The work was supported by DGICYT, projects PB91-0864 and PB94-0065. L.M.G. was funded by a CSIC Ph.D. studentship.Peer reviewe

Conformation of cytoskeletal elements during the division of infected Lupinus albus L. nodule cells

11 pages and figuresLupin nodule cells maintain their ability to divide for several cycles after being infected by endosymbiotic rhizobia. The conformation of the cytoskeletal elements of nodule cells was studied by fluorescence labelling, immunocytochemistry, and laser confocal and transmission electron microscopy. The dividing infected cells showed the normal microtubule and actin patterns of dividing plant cells. The clustered symbiosomes were tethered to the spindle-pole regions and moved to the cell poles during spindle elongation. In metaphase, anaphase, and early telophase, the symbiosomes were found at opposite cell poles where they did not interfere with the spindle filaments or phragmoplast. This symbiosome positioning was comparable with that of the organelles (which ensures organelle inheritance during plant cell mitosis). Tubulin microtubules and actin microfilaments appeared to be in contact with the symbiosomes. The possible presence of actin molecular motor myosin in nodules was analysed using a monoclonal antibody against the myosin light chain. The antigen was detected in protein extracts of nodule and root cytosol as bands of approximately 20 kDa (the size expected). In the nodules, an additional polypeptide of 65 kDa was found. Immunogold techniques revealed the antigen to be localized over thin microfilaments linked to the cell wall, as well as over the thicker microfilament bundles and surrounding the symbiosomes. The pattern of cytoskeleton rearrangement in dividing infected cells, along with the presence of myosin antigen, suggests that the positioning of symbiosomes in lupin nodule cells might depend on the same mechanisms used to partition genuine plant cell organelles during mitosisPeer reviewe

Distribución espacial y temporal de glicoproteínas durante el desarrollo de nodulos de lupino (Lupinus albus L.) cv. Multolupa

Trabajo presentado en la XVII Reunión Bienal de la Sociedad Española de Microscopía Electrónica, celebrada en Oviedo (España) del 5 al 8 de Abril de 1995