Transcriptome profiling of a Sinorhizobium meliloti fadD mutant reveals the role of rhizobactin 1021 biosynthesis and regulation genes in the control of swarming

58 pages, 7 figures, 3 tables, 3 additional files.-- Provisional PDF.[Background] Swarming is a multicellular phenomenom characterized by the coordinated and rapid movement of bacteria across semisolid surfaces. In Sinorhizobium meliloti this type of motility has been described in a fadD mutant. To gain insights into the mechanisms underlying the process of swarming in rhizobia, we compared the transcriptome of a S. meliloti fadD mutant grown under swarming inducing conditions (semisolid medium) to those of cells grown under non-swarming conditions (broth and solid medium).[Results] More than a thousand genes were identified as differentially expressed in response to growth on agar surfaces including genes for several metabolic activities, iron uptake, chemotaxis, motility and stress-related genes. Under swarming-specific conditions, the most remarkable response was the up-regulation of iron-related genes. We demonstrate that the pSymA plasmid and specifically genes required for the biosynthesis of the siderophore rhizobactin 1021 are essential for swarming of a S. meliloti wild-type strain but not in a fadD mutant. Moreover, high iron conditions inhibit swarming of the wild-type strain but not in mutants lacking either the iron limitation response regulator RirA or FadD.[Conclusions] The present work represents the first transcriptomic study of rhizobium growth on surfaces including swarming inducing conditions. The results have revealed major changes in the physiology of S. meliloti cells grown on a surface relative to liquid cultures. Moreover, analysis of genes responding to swarming inducing conditions led to the demonstration that iron and genes involved in rhizobactin 1021 synthesis play a role in the surface motility shown by S. meliloti which can be circumvented in a fadD mutant. This work opens a way to the identification of new traits and regulatory networks involved in swarming by rhizobia.JN was supported by a postdoctoral contract (Consejería de Innovación, Ciencia y Empresa, Junta de Andalucía). This work was supported by a FPI fellowship from MICINN to CVA-G, and by grants BIO2007-62988 and CVI 03541 to MJS.Peer reviewe

Is serology a realistic approach for monitoring red deer tuberculosis in the field?

Tuberculosis (TB) is a zoonotic mycobacterial infection with great importance in human health, animal production, and wildlife conservation. Although an ambitious eradication programme in cattle has been implemented for decades, TB-free status has not yet been achieved in most of Spain, where animal TB persists in a multi-host system of domestic and wild hosts, including the red deer (Cervus elaphus). However, information on long time series and trends of TB prevalence in wildlife is scarce. The diagnosis of TB in wild red deer is often based on gross pathology and bacteriological culture confirmation, although recently serological assays have been developed to detect anti- Mycobacterium tuberculosis Complex (MTC) antibodies. Particularly, protein complex P22 has demonstrated to yield good specificity and sensitivity in the serological diagnosis of MTC for red deer, as well as cattle, goats, sheep, pigs, wild boar, and European badger. Thus, the objective of the present study was to compare the performance of the P22-ELISA with TB-compatible lesion detection, as well as to assess the potential application of each technique for determining spatiotemporal trends and risk factors of MTC infection in wild red deer from low and high TB prevalence areas of Spain over the last two decades. We tested 5095 sera from 13 wild populations by indirect ELISA using P22 as antigen. Mean seroprevalence (13.22%, CI95: 12.32–14.18) was compared with the prevalence of macroscopic TB-compatible lesions (6.94%, CI95: 6.18–7.79). The results evidenced a poor agreement between both techniques (K < 0.3), although generalized TB-lesions and anti-P22 antibodies showed a positive association (¿² = 9.054, P = 0.004). Consequently, TB-lesion based prevalence and seroprevalence cannot be considered as equivalent for TB surveillance in red deer. Regarding the spatiotemporal trend of TB in red deer in Spain, we observed a North-South gradient of TB occurrence North: 1.23% (CI95: 0.77–1.97) of TB-lesions and 12.55% (CI95: 10.91–14.41) of P22-ELISA; Centre: 7.10% (CI95: 6.04–8.33) and 8.74% (CI95: 7.57–10.08); South: 21.04% (CI95:17.81–24.69) and 23.09% (CI95: 19.73–26.84), respectively]. Overall, there was a stability over time, with higher prevalence in adults belonging to densely populated sites. We conclude that the P22-ELISA alone is not sufficiently reliable for TB surveillance in red deer at large spatiotemporal scales. Instead, we recommend combining gross pathology and P22-ELISA

Comparación de métodos para el seguimiento de las poblaciones de comadreja Mustela nivalis en ambientes agrícolas

La comadreja Mustela nivalis es un pequeño carnívoro especializado en el consumo de micromamíferos. En la Península Ibérica hay muy poca información sobre esta especie, siendo especialmente interesante el estudio de su papel en la regulación de la dinámica poblacional de los micromamíferos. Algunas especies alcanzan eventualmente elevadas densidades en ambientes agrícolas, generando notable alarma social ya que pueden mermar significativamente la producción agrícola. Cualquier estudio de esta naturaleza requiere de métodos efectivos de seguimiento a largo plazo de las poblaciones de este mustélido. En este trabajo evaluamos la eficacia y eficiencia de cuatro metodologías para detectar comadrejas en ambientes agrarios: captura en vivo, trampas de huellas, trampas de pelo y cámaras-trampa. El estudio se desarrolló en dos localidades agrícolas de la meseta Castellano-Leonesa. Se hicieron dos muestreos por localidad, en otoño y primavera de 2016/2017. En cada localidad seleccionamos 10 lindes de ~400 m de longitud, donde se instalaron de forma alterna y equidistante: 6 trampas de captura, 2 trampas de huellas, 2 trampas de pelos y 1 cámara-trampa, que estuvieron activos entre 9-10 días. Se usó carne de pollo y topillo Microtus arvalis como cebo. Se detectó la presencia de comadrejas con alguna de las metodologías en el 38% de las lindes muestreadas (ocupación estimada), con un total de 29 detecciones (13 otoño/16 primavera). El trampeo en vivo detectó la presencia en el 80% de las lindes positivas, las trampas de huella en el 33%, las cámaras-trampa en el 20% y las trampas de pelo en el 6%. La ocupación estimada estuvo relacionada positivamente con las tasas de detección (detecciones/100 trampas-día) del trampeo en vivo y de las trampas de huellas pero no con las de cámaras-trampa y trampas de pelo. Al tener en cuenta el esfuerzo (trampas-día), las trampas de pelo fueron el método menos eficiente para detectar comadrejas. Estos resultados indican que, con esfuerzos similares, las trampas de huellas y las cámaras-trampa pueden ser tan eficaces como el trampeo en vivo para detectar comadrejas en ambientes agrícolas con condiciones similares a las de nuestro estudio.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

SARS-CoV-2 Infection in Multiple Sclerosis

To understand COVID-19 characteristics in people with multiple sclerosis (MS) and identify high-risk individuals due to their immunocompromised state resulting from the use of disease-modifying treatments. Retrospective and multicenter registry in patients with MS with suspected or confirmed COVID-19 diagnosis and available disease course (mild = ambulatory; severe = hospitalization; and critical = intensive care unit/death). Cases were analyzed for associations between MS characteristics and COVID-19 course and for identifying risk factors for a fatal outcome. Of the 326 patients analyzed, 120 were cases confirmed by real-time PCR, 34 by a serologic test, and 205 were suspected. Sixty-nine patients (21.3%) developed severe infection, 10 (3%) critical, and 7 (2.1%) died. Ambulatory patients were higher in relapsing MS forms, treated with injectables and oral first-line agents, whereas more severe cases were observed in patients on pulsed immunosuppressors and critical cases among patients with no therapy. Severe and critical infections were more likely to affect older males with comorbidities, with progressive MS forms, a longer disease course, and higher disability. Fifteen of 33 patients treated with rituximab were hospitalized. Four deceased patients have progressive MS, 5 were not receiving MS therapy, and 2 were treated (natalizumab and rituximab). Multivariate analysis showed age (OR 1.09, 95% CI, 1.04-1.17) as the only independent risk factor for a fatal outcome. This study has not demonstrated the presumed critical role of MS therapy in the course of COVID-19 but evidenced that people with MS with advanced age and disease, in progressive course, and those who are more disabled have a higher probability of severe and even fatal diseas

Planificación y diseño de recursos para poner en marcha la versión on-line del Máster oficial las TIC en Educación

Memoria ID-0180. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2014-2015

Identificación y caracterización de genes de osmoadaptación en Rhizobium y de su papel en simbiosis con leguminosas

Tesis Univ. Granada. Departamento de Fisiología Vegetal. Leída el 16 de noviembre de 200

Increased trehalose biosynthesis improves Mesorhizobium ciceri growth and symbiosis establishment in saline conditions

Cicer arietinum (chickpea) is a legume very sensitive to salinity, and so are most of its rhizobial symbionts belonging to the species Mesorhizobium ciceri. We observed that exogenous trehalose (i.e., added to the growth medium) can significantly improve growth of M. ciceri strain Rch125 under moderate salinity. In order to test if endogenous trehalose (i.e., synthesized by the cell) could also enhance salt tolerance, strain Rch125 was genetically modified with various trehalose biosynthesis genes from Sinorhizobium meliloti 1021 (otsA, treS, treY) and Mesorhizobium loti MAFF 303099 (otsAB). We found that overexpression of otsA or otsAB, but not treS or treY, significantly improved M. ciceri Rch125 growth in saline media. This growth improvement correlated with enhanced trehalose accumulation in otsA- and otsAB-modified cells, suggesting that increased trehalose synthesis via trehalose-6-phosphate can enhance bacterial salt tolerance. Chickpea plants inoculated with M. ciceri Rch125 derivatives carrying extra otsAB or otsA genes formed more nodules and accumulated more shoot biomass than wild type inoculated plants when grown in the presence of NaCl. These results support the notion that improved salt tolerance of the bacterial symbiont can alleviate the negative effects of salinity on chickpeas, and that such improvement in M. ciceri can be achieved by manipulating trehalose metabolism.This work was supported by grants AECI 173/03/P and AECI A/6935/06 from Agencia Española de Cooperación Internacional to JS and BB, and grants BIO2005-08089-C02-01 (Ministerio de Educación y Ciencia, Spain) and BIO2008-02447 (Ministerio de Ciencia e Innovación) to JS. Help by Rebeca Pérez-Arnedo is gratefully acknowledged.Peer Reviewe

An Overdose of the Arabidopsis Coreceptor BRASSINOSTEROID INSENSITIVE1-ASSOCIATED RECEPTOR KINASE1 or Its Ectodomain Causes Autoimmunity in a SUPPRESSOR OF BIR1-1-Dependent Manner

The membrane-bound Brassinosteroid insensitive1-associated receptor kinase1 (BAK1) is a common coreceptor in plants and regulates distinct cellular programs ranging from growth and development to defense against pathogens. BAK1 functions through binding to ligand-stimulated transmembrane receptors and activating their kinase domains via transphosphorylation. In the absence of microbes, BAK1 activity may be suppressed by different mechanisms, like interaction with the regulatory BIR (for BAK1-interacting receptor-like kinase) proteins. Here, we demonstrated that BAK1 overexpression in Arabidopsis (Arabidopsis thaliana) could cause detrimental effects on plant development, including growth arrest, leaf necrosis, and reduced seed production. Further analysis using an inducible expression system showed that BAK1 accumulation quickly stimulated immune responses, even under axenic conditions, and led to increased resistance to pathogenic Pseudomonas syringae pv tomato DC3000. Intriguingly, our study also revealed that the plasma membrane-associated BAK1 ectodomain was sufficient to induce autoimmunity, indicating a novel mode of action for BAK1 in immunity control. We postulate that an excess of BAK1 or its ectodomain could trigger immune receptor activation in the absence of microbes through unbalancing regulatory interactions, including those with BIRs. Consistently, mutation of suppressor of BIR1-1, which encodes an emerging positive regulator of transmembrane receptors in plants, suppressed the effects of BAK1 overexpression. In conclusion, our findings unravel a new role for the BAK1 ectodomain in the tight regulation of Arabidopsis immune receptors necessary to avoid inappropriate activation of immunity

Role of Potassium Uptake Systems in Sinorhizobium meliloti Osmoadaptation and Symbiotic Performance▿

Stimulation of potassium uptake is the most rapid response to an osmotic upshock in bacteria. This cation accumulates by a number of different transport systems whose importance has not been previously addressed for rhizobia. In silico analyses reveal the presence of genes encoding four possible potassium uptake systems in the genome of Sinorhizobium meliloti 1021: Kup1, Kup2, Trk, and Kdp. The study of the relevance of these systems under a number of different growth conditions and in symbiosis showed that the integrity of Kup1 or Trk is essential for growth under laboratory conditions even in osmotically balanced media and the absence of both systems leads to a reduced infectivity and competitiveness of the bacteria in alfalfa roots. Trk is the main system involved in the accumulation of potassium after an osmotic upshift and the most important system for growth of S. meliloti under hyperosmotic conditions. The other three systems, especially Kup1, are also relevant during the osmotic adaptation of the cell, and the relative importance of the Kdp system increases at low potassium concentrations