Pseudomonas aeruginosa That Specifically Mediates Chemotaxis Toward α-Ketoglutarate

Pseudomonas aeruginosa is an ubiquitous pathogen able to infect humans, animals, and plants. Chemotaxis was found to be associated with the virulence of this and other pathogens. Although established as a model for chemotaxis research, the majority of the 26 P. aeruginosa chemoreceptors remain functionally un-annotated. We report here the identification of PA5072 (named McpK) as chemoreceptor for α-ketoglutarate (αKG). High-throughput thermal shift assays and isothermal titration calorimetry studies (ITC) of the recombinant McpK ligand binding domain (LBD) showed that it recognizes exclusively α-ketoglutarate. The ITC analysis indicated that the ligand bound with positive cooperativity (Kd1 = 301 μM, Kd2 = 81 μM). McpK is predicted to possess a helical bimodular (HBM) type of LBD and this and other studies suggest that this domain type may be associated with the recognition of organic acids. Analytical ultracentrifugation (AUC) studies revealed that McpK-LBD is present in monomer-dimer equilibrium. Alpha-KG binding stabilized the dimer and dimer self-dissociation constants of 55 μM and 5.9 μM were derived for ligand-free and αKG-bound forms of McpK-LBD, respectively. Ligand-induced LBD dimer stabilization has been observed for other HBM domain containing receptors and may correspond to a general mechanism of this protein family. Quantitative capillary chemotaxis assays demonstrated that P. aeruginosa showed chemotaxis to a broad range of αKG concentrations with maximal responses at 500 μM. Deletion of the mcpK gene reduced chemotaxis over the entire concentration range to close to background levels and wild type like chemotaxis was recovered following complementation. Real-time PCR studies indicated that the presence of αKG does not modulate mcpK expression. Since αKG is present in plant root exudates it was investigated whether the deletion of mcpK altered maize root colonization. However, no significant changes with respect to the wild type strain were observed. The existence of a chemoreceptor specific for αKG may be due to its central metabolic role as well as to its function as signaling molecule. This work expands the range of known chemoreceptor types and underlines the important physiological role of chemotaxis toward tricarboxylic acid cycle intermediates. [EN]FEDER funds and Fondo Social Europeo through grants from the Junta de Andalucía (grant CVI-7335) and the Spanish Ministry for Economy and Competitiveness (grant BIO2013-42297). MM was supported by the Spanish Ministry of Economy and Competitiveness Postdoctoral Research Program, Juan de la Cierva (JCI-2012-11815).Peer reviewe

Concentration Dependent Effect of Plant Root Exudates on the Chemosensory Systems of Pseudomonas putida KT2440

Plant root colonization by rhizobacteria can protect plants against pathogens and promote plant growth, and chemotaxis to root exudates was shown to be an essential prerequisite for efficient root colonization. Since many chemoattractants control the transcript levels of their cognate chemoreceptor genes, we have studied here the transcript levels of the 27 Pseudomonas putida KT2440 chemoreceptor genes in the presence of different maize root exudate (MRE) concentrations. Transcript levels were increased for 10 chemoreceptor genes at low MRE concentrations, whereas almost all receptor genes showed lower transcript levels at high MRE concentrations. The exposure of KT2440 to different MRE concentrations did not alter c-di-GMP levels, indicating that changes in chemoreceptor transcripts are not mediated by this second messenger. Data suggest that rhizosphere colonization unfolds in a temporal fashion. Whereas at a distance to the root, exudates enhance chemoreceptor gene transcript levels promoting in turn chemotaxis, this process is reversed in root vicinity, where the necessity of chemotaxis toward the root may be less important. Insight into KT2440 signaling processes were obtained by analyzing mutants defective in the three cheA paralogous genes. Whereas a mutant in cheA1 showed reduced c-di-GMP levels and impaired biofilm formation, a cheA2 mutant was entirely deficient in MRE chemotaxis, indicating the existence of homologs of the P. aeruginosawsp and che (chemotaxis) pathways. Signaling through both pathways was important for efficient maize root colonization. Future studies will show whether the MRE concentration dependent effect on chemoreceptor gene transcript levels is a feature shared by other species

RecA Protein Plays a Role in the Chemotactic Response and Chemoreceptor Clustering of Salmonella enterica

The RecA protein is the main bacterial recombinase and the activator of the SOS system. In Escherichia coli and Salmonella enterica sv. Typhimurium, RecA is also essential for swarming, a flagellar-driven surface translocation mechanism widespread among bacteria. In this work, the direct interaction between RecA and the CheW coupling protein was confirmed, and the motility and chemotactic phenotype of a S. Typhimurium ΔrecA mutant was characterized through microfluidics, optical trapping, and quantitative capillary assays. The results demonstrate the tight association of RecA with the chemotaxis pathway and also its involvement in polar chemoreceptor cluster formation. RecA is therefore necessary for standard flagellar rotation switching, implying its essential role not only in swarming motility but also in the normal chemotactic response of S. Typhimurium.National Institutes of Health (U.S.) (Grant 1R01GM100473

Low prevalence of vancomycin-resistant enterococci in clinical samples from hospitalized patients of the Canary Islands, Spain

Over the last decade vancomycin-resistant enterococci (VRE) have emerged as nosocomial pathogens. The aim of this study was to determine the prevalence of VRE in clinical samples from hospitalized patients in the Canary Islands. From April to November 2000, 437 enterococci were isolated from patients hospitalized at the four main health care centers in those islands. Identification to the species level was performed with the GPS-TA (Vitek 1) or the Wider I system. A PCR assay was used to determine the genotype of glycopeptide resistance (vanA, vanB, vanC1, and vanC2/C3 genes). Only three (0.7%) VRE were detected: one vanA Enterococcus faecalis, and two vanC1 Enterococcus gallinarum. To our knowledge, this is the first VRE study carried out in the Canary Islands hospitals, and the results showed a low prevalence of VRE

Chemoperception of Specific Amino Acids Controls Phytopathogenicity in Pseudomonas syringae pv. tomato

IMPORTANCE There is substantive evidence that chemotaxis is a key requisite for efficient pathogenesis in plant pathogens. However, information regarding particular bacterial chemoreceptors and the specific plant signal that they sense is scarce. Our work shows that the phytopathogenic bacterium Pseudomonas syringae pv. tomato mediates not only chemotaxis but also the control of pathogenicity through the perception of the plant abundant amino acids Asp and Glu. We describe the specificity of the perception of L- and D-Asp and L-Glu by the PsPto-PscA chemoreceptor and the involvement of this perception in the regulation of pathogenicity-related traits. Moreover, a saturating concentration of D-Asp reduces bacterial virulence, and we therefore propose that ligand-mediated interference of key chemoreceptors may be an alternative strategy to control virulence.Supplemental material for this article may be found at https://doi.org/10.1128/mBio .01868-19.We acknowledge M. Trini Gallegos for kindly provide plasmid pCdrA::gfpS and S. Nebreda for technical assistance.Chemotaxis has been associated with the pathogenicity of bacteria in plants and was found to facilitate bacterial entry through stomata and wounds. However, knowledge regarding the plant signals involved in this process is scarce. We have addressed this issue using Pseudomonas syringae pv. tomato, which is a foliar pathogen that causes bacterial speck in tomato. We show that the chemoreceptor P. syringae pv. tomato PscA (PsPto-PscA) recognizes specifically and with high affinity L-Asp, L-Glu, and D-Asp. The mutation of the chemoreceptor gene largely reduced chemotaxis to these ligands but also altered cyclic di-GMP (c-di-GMP) levels, biofilm formation, and motility, pointing to cross talk between different chemosensory pathways. Furthermore, the PsPto-PscA mutant strain showed reduced virulence in tomato. Asp and Glu are the most abundant amino acids in plants and in particular in tomato apoplasts, and we hypothesize that this receptor may have evolved to specifically recognize these compounds to facilitate bacterial entry into the plant. Infection assays with the wild-type strain showed that the presence of saturating concentrations of D-Asp also reduced bacterial virulence.This work was supported by grants AGL2015-63851-R and RTI2018-095222-B100 (to E.L.-S.) and BIO2016-76779-P (to T.K.) from the Ministerio de Economía y Competitividad, Spain. J.P.C.-V. was supported by the FPI program (BES-2016-076452, MINECOSpain)

Nanotechnology and the Treatment of HIV Infection

Suboptimal adherence, toxicity, drug resistance and viral reservoirs make the lifelong treatment of HIV infection challenging. The emerging field of nanotechnology may play an important role in addressing these challenges by creating drugs that possess pharmacological advantages arising out of unique phenomena that occur at the “nano” scale. At these dimensions, particles have physicochemical properties that are distinct from those of bulk materials or single molecules or atoms. In this review, basic concepts and terms in nanotechnology are defined, and examples are provided of how nanopharmaceuticals such as nanocrystals, nanocapsules, nanoparticles, solid lipid nanoparticles, nanocarriers, micelles, liposomes and dendrimers have been investigated as potential anti-HIV therapies. Such drugs may, for example, be used to optimize the pharmacological characteristics of known antiretrovirals, deliver anti-HIV nucleic acids into infected cells or achieve targeted delivery of antivirals to the immune system, brain or latent reservoirs. Also, nanopharmaceuticals themselves may possess anti-HIV activity. However several hurdles remain, including toxicity, unwanted biological interactions and the difficulty and cost of large-scale synthesis of nanopharmaceuticals

Ceniza y lava: revelaciones científicas junto al volcán

Para la exposición se ha contado con el apoyo del Museo de la Ciencia y el Cosmos (La Laguna, Tenerife) del Cabildo de Tenerife, uno de los centros más visitados en la comunidad canaria por su enfoque interactivo de la divulgación científica. Ceniza y lava acerca el fenómeno geológico al público general para que experimente y comprenda la naturaleza, promoviendo la percepción de lo plausible en nuestro entorno y que adquiera conocimientos básicos para actuar. A diferencia de otros eventos divulgativos similares, esta exposición busca acercar a la población la experiencia investigadora implementada por tierra, mar y aire con sus hallazgos: materiales recopilados, metodologías utilizadas y conclusiones adquiridas, y lo hace de una manera inmersiva, interactiva y didáctica. La exhibición, programada del 29 de junio de 2023 al 30 de junio de 2024, permite ver, y en algunos casos manipular, materiales e instrumentos utilizados en las investigaciones y que por primera vez se han recopilado y museizado para ser exhibidos. Se compone de dos partes: 1) Ceniza y lava. En esta primera sala se recrea la erupción a través de diversos elementos: proyecciones impactantes, datos clave en una pared, línea del tiempo geológica de La Palma, visión nocturna de la erupción a gran escala, evolución diaria de las coladas sobre una reproducción 3D de la isla de 2 m de longitud y caleidoscopio inmersivo de un tubo lávico. 2) Revelaciones científicas. La transición de una sala a otra se realiza a través de una carpa, réplica de un puesto de mando avanzado que sirvió de zona de trabajo, reunión, atención a medios e incluso de descanso del personal investigador. En la segunda sala se accede a materiales, herramientas y descubrimientos realizados en la erupción desde las perspectivas de tierra, mar y aire. Esta exposición es fruto de la sinergia entre el personal científico de los centros CSIC en Canarias que se desplazó a la erupción y el de otras entidades como GE3BCN, el servicio de PRL del CSIC, el MUNA o el GES del Gobierno de Canarias, entre otros.Los equipos de investigación de los centros de la Delegación del CSIC en Canarias (IPNA, IEO e IGME) desempeñaron un papel crucial en la erupción de La Palma abordándola desde diferentes perspectivas: tierra, mar y aire. Su misión: entender el comportamiento del volcán y proporcionar información valiosa a las autoridades locales y equipos de emergencias para la toma de decisiones en gestión de desastres y protección de la población. Con idea de visibilizar este trabajo, esta labor se plasmó en una exposición 360° que es un testimonio poderoso de cómo la colaboración científica puede iluminar fenómenos naturales y su impacto en nuestra comunidad.FECYTOrganismo Autónomo de Museos y Centros de Tenerife (OAMC)Delegación del CSIC en CanariasPeer reviewedEnlace a la visita virtual de la exposición: https://meta.yonders.io/tour/museo-ciencia-y-cosmo

Informe final del escaneo de horizonte sobre futuras especies exóticas invasoras en España

73 p.La introducción de especies exóticas invasoras (EEI) es una de las principales causas de la pérdida de biodiversidad a nivel global, que provoca grandes costes socioeconómicos. Sin embargo, el número de nuevas introducciones continúa creciendo año tras año. Por lo tanto, urge identificar posibles futuras EEI con el objetivo de diseñar e implementar medidas que prevengan y mitiguen los efectos negativos de su introducción. Así, el objetivo de este estudio es prospectar qué especies exóticas no establecidas en España podrían llegar fácilmente en los próximos 10 años, establecerse y causar importantes impactos ecológicos. Para ello, se ha realizado un escaneo de horizonte, siguiendo la metodología establecida en trabajos previos, siendo el primero para el conjunto de las especies exóticas invasoras en España. Se añadieron en el análisis especies que no son autóctonas de España, incluyendo los archipiélagos de Canarias y Baleares, y que no están establecidas en España. Un total de 39 científicos, expertos en distintos grupos taxonómicos y ecosistemas, ha evaluado 933 especies. Con el objetivo de analizar el acuerdo entre las evaluaciones individuales de los expertos y su consistencia, se llevaron a cabo dos análisis de fiabilidad complementarios, cuyos resultados se discuten en este informe. Como resultado del escaneo, se obtuvo una lista priorizada de 105 especies (46 con riesgo muy alto y 59 con riesgo alto). La mayoría de estas especies (84,8%), sin embargo, no están incluidas actualmente en el Catálogo Español de Especies Exóticas Invasoras. Por lo tanto, se recomienda la realización de un análisis de riesgo más detallado de estas especies y, si se confirma el riesgo alto, la solicitud de su incorporación en dicho catálogo o en el Listado de especies alóctonas susceptibles de competir con las especies silvestres autóctonas, alterar su pureza genética o los equilibrios ecológicos. Del mismo modo, se propone la realización de escaneos de horizonte específicos para los archipiélagos de Canarias y Baleares, ya que muchas de las especies autóctonas de la Península no lo son de las islas y podrían tener un gran impacto si allí se introdujeran. Este informe también analiza la afinidad taxonómica (i.e. filo) y funcional (i.e. productor primario, depredador, omnívoro, herbívoro o filtrador) de las especies de la lista priorizada, su origen geográfico y las principales vías de introducción. Por último, discute los mecanismos de impacto de dichas especies.Ministerio de Ciencia e Innovació