Toxicity of phenolic compounds extracted from bark residues of different ages

In Quebec, Canada, industrial bark wastelands cover several hundred hectares of land. Bark residue that has piled up for decades tends to remain free of vegetation for years. To assess the revegetation potential of such sites, we sought to determine those factors responsible for poor plant growth. Phenolic compounds from fresh to 20-year-old bark residues were extracted with four solvents and quantified by high-performance liquid chromatography (HPLC). We simulated solutions (mixtures of standard phenolic compounds) to evaluate the potential toxic effects of phenolic compounds on the rhizobial growth, germination index, plant growth, nodule number, and nitrogen fixation activity of two legume species under laboratory conditions. The concentration of individual phenolic compounds varied from none detected to 350 µg/g bark residue. The extracted phenolic compounds differed among solvents and bark residues. The highest concentration of total phenolic compounds was from fresh bark; most of these were soluble in water or 0.1 M NaOH. For older bark residues, the total phenolic content depended on solvent strength, generally in the order of 2.0 M NaOH > 0.1 M NaOH = hot water > cold water. The biological activity of the simulated bark extracts was not established with the rhizobial growth inhibition test but with the germination index and rhizobium–legume symbiosis tests. With these, the toxicity of the simulated phenolic extracts decreased from fresh to the older bark residues. Plant dry weight, nodule number, and nitrogen fixation activity of vetch (Vicia sativa L.) were less negatively affected by high concentrations of phenolics than birdsfoot trefoil (Lotus corniculatus L.), although birdsfoot trefoil grew at lower concentrations. The rhizobium–legume symbiosis has potential for revegetating bark wastelands with less than 1 year old and older bark residues

Absence of correlation between nitrate reductase and symbiotic nitrogen fixation efficiency in rhizobium meliloti

Les activités spécifiques des nitrates réductases assimilatoires et "régulatoires" ont été étudiées chez 41 souches de Rhizobium meliloti ayant des activités différentes de fixation symbiotique d’azote. Les deux nitrates réductases ont été retrouvées chez les souches très efficaces ainsi que chez les souches inefficaces et aucune corrélation significative n’a été trouvée entre les activités spécifiques et le rendement de la matière sèche de la luzerne obtenu avec les 41 souches à l’essai. La détermination des activités spécifiques de ces deux nitrates réductases chez les bactéries végétatives ne peut donc pas être utilisée comme un test physiologique rapide pour la sélection de souches très efficaces de R. meliloti.Specific activities of the assimilatory and "regulatory" types of nitrate reductase were studied in 41 strains of Rhizobium m,eliloti naving ditierent symbiotic nitrogen fixation activities. Both nitrate reductase enzymes were present in very effective ind ineffective strains and no significant correlation was iound between the specific activities of the two enzymes and the dry matter yields of alfalfa obtained with the 41 strains. Measurements of the specific activities of the two nitrate reductase enzymes in the vegetative bacteria cannot be used as a rapid physiological test for the seiection of very effective strains of R. meliloti

Isolation of free-living dinitrogen-fixing bacteria and their activity in compost containing de-inking paper sludge

Knowledge of the microbiology of dinitrogen (N2)-fixing bacteria in compost rich in de-inking paper sludge (DPS) is limited. Dinitrogen (N2)-fixing bacteria from DPS composts were isolated and studied for their N2-fixing activity in vitro and in vivo. Two Gram-negative N2-fixing isolates were identified as Pseudomonas. At 20 C, both isolates revealed that N2-fixing activity was higher than that of three arctic Pseudomonas strains. Their N2-fixing activity was found to occur between 18 and 25 C, a pattern that was similar to the reference isolate Azotobacter ATCC 7486. Composts successfully showed N2-fixing activity after carbohydrate amendments both with and without inoculation of a N2-fixing isolate. These results suggest that DPS composts support N2-fixing bacteria and that N2-fixing activity is dependent on a usable carbohydrate source. 2005 Elsevier Ltd. All rights reserved.Keywords: Dinitrogen-fixing bacteria; Compost; Paper sludge; Glucose; Pseudomonas balearica; Pseudomonas putid

Stressed and distressed: how is the COVID-19 pandemic associated with sexual frequency, sexual satisfaction, and relationship satisfaction?

Background: The Canadian government’s response to the ongoing COVID-19 pandemic included the implementation of several restrictive measures since March 2020. These actions sought to decrease social contact and increase physical distancing, including that within universities. Such constraints were required to impede the transmission of the virus; however, concerns remain about their impact on the sexual and intimate relationships of university employees and students. Aim: This study examined the associations between COVID-19–related stress and sexual frequency, sexual satisfaction, and relationship satisfaction, also testing the mediating role of psychological distress. Methods: The models were tested with Canadian data collected from university employees and students in 2 phases: the first wave in April-May 2020 (T1; n = 2754) and the second wave in November-December 2021 (T2; n = 1430), 18 months afterward. Participants completed self-report questionnaires online. Path analyses were performed to test the associations of the mediation models. Outcomes: The principal outcomes included psychological distress determined via the Patient Health Questionnaire–4, relationship satisfaction measured via the Dyadic Adjustment Scale, and sexual satisfaction and sexual frequency ascertained through a single item each. Results: Overall, COVID-19–related stress was associated with higher psychological distress, which in turn was related to lower sexual frequency, sexual satisfaction, and relationship satisfaction. Similar results were obtained with T1 and T2 data, indicating the mediating effect of psychological distress. Clinical implications: These findings increase scholarly comprehension of the negative associations between stress/distress and sexual and romantic relationships. Sexuality and close relationships are vital to the quality of human life; thus, targeted interventions should be developed to reduce COVID-19–related stress and its impact on sexual and romantic relationships to mitigate the long-term influences of this unique global challenge. Strengths & Limitations: To our knowledge, this study is the first to use a large sample size and replicate findings in 2 waves. Nonetheless, it is limited by the use of cross-sectional data. Longitudinal studies with the same participants are mandated to better understand the evolution of these outcomes. Conclusion: COVID-19–related stress and psychological distress were found among participating university students and employees and were associated with lower sexual satisfaction, sexual frequency, and intimate relationship satisfaction. These results were observed at the early onset of the pandemic and 18 months afterward, suggesting that the stress generated by the pandemic were not mere reactions to the onset of the pandemic but persisted over time

Effets de l'inoculation avec des souches de <i>Rhizobium leguminosarum</i> biovar <i>trifolii</i> sur la croissance du blé dans deux sols du Maroc

One hundred strains of Rhizobium leguminosarum bv. trifolii were isolated from roots of wheat cultivated in rotation with clover in two different regions of Morocco. The isolates were first screened for their effect on the growth of the cultivar Rihane of wheat cultivated in an agricultural soil under greenhouse conditions. After 5 weeks of growth, 14 strains stimulating the fresh or dry matter yield of shoots were selected and used in a second pot inoculation trial performed with two different agricultural soils. The results show that the strains behaved differently according to the soil used. In the loamy sand Rabat, strain IAT 168 behaved potentially like a plant growth promoting rhizobacteria (PGPR), as indicated by the 24% increases (P < 0.1) observed in wheat shoot dry matter and grain yields. In the silty clay Merchouch, no PGPR activity was observed, and 6 strains showed a significant deleterious effect on yields. These observations suggest that it is very important in a crop rotation system to choose a R. leguminosarum bv. trifolii strain that is effective with clover and shows PGPR activity with wheat to avoid deleterious effects on wheat yields.Cent souches de Rhizobium leguminosarum bv. trifolii ont été isolées à partir du blé cultivé en rotation avec le trèfle dans deux différentes régions du Maroc. Les isolats ont été d'abord criblés pour leur effet sur la croissance de la variété Rihane de blé cultivé dans un sol agricole sous conditions de serre. Après 5 semaines de croissance, 14 souches stimulant le rendement en matière fraîche ou en matière sèche des tiges ont été sélectionnées et utilisées dans un deuxième essai de croissance en pots en utilisant deux sols agricoles différents. Les résultats montrent que les souches ont eu un comportement différent selon le sol utilisé. Dans le sable loameux Rabat la souche IAT 168 de R. leguminosarum bv. trifolii semble avoir un bon potentiel comme rhizobactérie favorisant la croissance des plantes (RFCP) avec le blé. En effet dans ce sol, la souche IAT 168 a augmenté (P < 0,1) le rendement de la matière sèche des tiges et le rendement en grains d'environ 24 % par rapport au témoin non inoculé. Dans l'argile limoneuse Merchouch aucune souche ne s'est comportée en RFCP, et 6 souches ont eu un effet délétère significatif (P < 0,05) sur le rendement du blé. Ces observations indiquent qu'il est très important dans un système de rotation de choisir une souche de Rhizobium leguminosarum bv. trifolii à la fois efficace avec le trèfle et RFCP avec le blé, afin d'éviter les effets délétères sur le rendement du blé

Eficiencia simbiótica de rizobios nativos de Sancti Spíritus, Cuba, inoculados en Centrosema molle

Se realizó un ensayo en invernadero, con el objetivo de determinar la eficiencia simbiótica de 39 cepas nativas de bradyrizobios procedentes de Sancti Spíritus. Los aislamientos se hicieron a partir de nódulos radicales de Centrosema molle, Centrosema virginianum y Centrosema plumieri, los cuales son macrosimbiontes provenientes de las zonas centro y sur de Sancti Spíritus. Las cepas obtenidas se inocularon en C. molle, leguminosa forrajera promisoria para la alimentación del ganado en el territorio. Los métodos de inoculación fueron estándares, acorde con lo recomendado en la literatura internacional. El diseño experimental fue de bloques al azar, con 41 tratamientos y tres réplicas. Se realizó análisis de varianza (ANOVA) y se evaluó el peso seco de la parte aérea de la planta, el peso seco radical, el índice de nodulación y el rendimiento de nitrógeno. Se concluye que existió una alta eficiencia simbiótica de las cepas nativas de la zona centro, al ser inoculadas en una leguminosa perteneciente a la misma zona; mientras que las de la zona sur fueron ineficientes en dicha leguminosa. Por otra parte, JK3 (C. virginianum), HG1 (C. plumieri) ambas de la zona centro, SP20 (C. molle, zona sur) y JJ2 (C. virginianum, zona centro) presentaron altos índices de eficiencia en la leguminosa evaluada, lo que las convierte en las más promisorias. Los altos índices de nodulación de JH4, JJ2, JJ7, JK6, JK1 y JK5 (C. virginianum) no implicaron una alta eficiencia simbiótica. Se recomienda una fase de selección en condiciones de campo, con diferentes macrosimbiontes y en condiciones edafoclimáticas estresantes

Efecto de la inoculación con bacterias rizosféricas en dos variedades de trigo. Fase I: condiciones controladas

The experiment was carried out in a greenhouse so that the inoculation, both simple and combined (with the rhizospheric bacteria- Sinorhizobium and Azospirllium), en two varieties of Wheat. Materials and methodologies were used in accordance with previously prescribed conventional methodologies for this study. The experimental design was completely randomized, with 4 replicas and 10 treatments. A statistical analysis using two-way variance was done. Fertilized treatment was applied with NH4NO3 (150 ppm/kg soil). The content of chlorophyll foliage was evaluated, dry air weight, dry root weight, length of stem, and germination. In the event that differences appeared, it was determined through use of the Duncan Test, and the differences between varieties with t-Student. It is concluded that combined inoculation with the strain A2 (Sinorhizobium meliloti) and the strain N7 (Azospirillum zeae) had the greatest positive influence on the chlorophyll content of the plants. On the other hand, there was a great difference between the two varieties of wheat in terms of length of stem, dry air weight, and dry root weight. The results of dry air weight and dry root weight, upon combining the two factors that were studied, highly depended on the varietal characteristics of the plant and on the native population of rhizobacteria. The germination of the plants was not linked to any of the applied factors in the experiment.Se llevo a cabo un experimento bajo condiciones controladas para determinar la respuesta de dos variedades de trigo a la inoculacion simple y combinada realizada con Sinorhizobium y Azospirillum. Se utilizo una cepa de A. zeae, y dos cepas pertenecientes a S. meliloti. Los materiales y metodos aplicados correspondieron a lo descrito en las metodologias prestablecidas en este campo de estudio. Diseno experimental: completamente aleatorizado, con 20 tratamientos y 4 replicas. No se utilizo tratamiento fertilizado. Se evaluaron diferentes variables agronomicas, relacionadas con la arquitectura radical y la biomasa aerea. Analisis de varianza bifactorial. En caso de aparecer diferencias, se aplico analisis de varianza de un factor a la interaccion en primera instancia, o a los factores probados. Diferencias entre medias por LSD de Fisher. Se transformaron datos de conteo de digitos por �ãx. Se calculo correlacion y regresion multiple entre variables. Se concluye que la inoculacion combinada de Sinorhizobium con Azospirillum, asi como la inoculacion simple con Sinorhizobium, resultaron de alta importancia en las alternativas de inoculacion que se realizaron en el experimento. Existio una alta diferenciacion entre las dos variedades de trigo en determinadas variables agronomicas, lo que indica una influencia marcada de las caracteristicas varietales de las plantas. Se observó una fuerte relación estadística entre las variables peso seco aéreo y variables de la raíz para los tratamientos inoculados con A2 y A2+N7, respectivamente

Les comportements de santé des étudiants de première candidature de l'Université Libre de Bruxelles.

For several years, quality of life is used as a measure of health status. As university constitues a specific setting for young adults, the Health Service of the french-speaking Free University of Brussels initiated a survey in order to study health behaviours of students from the first grade. During the academic year 1998-99, 3,185 students were surveyed in the first degree, using an anonymous self-completed questionnaire with the following topics: health perception, weight, social support, emotional well-being, tobacco, alcohol, medicines, cannabis and ecstasy use as well as access to general practitioner. Body Mass Index was computed and emotional well-being was approached using CES-D scale. Results are presented by gender and faculty. Mutivariate analysis was also realised using logistic regression. In general, results confirm the data resulting from other studies in general population as well as at school. Nevertheless, results show that health is a problem for a minority of students and is a "whole" that has to be approached globally. Moreover, data give a basis to define priorities and strategies to improve students' physical and mental well-being at university. Results are also useful to better target these actions to those at needs.English AbstractJournal ArticleSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Ensifer, Phyllobacterium and Rhizobium species occupy nodules of Medicago sativa (alfalfa) and Melilotus alba (sweet clover) grown at a Canadian site without a history of cultivation

Correspondance: Bromfield E.S.P. [email protected] audiencePhage-resistant and -susceptible bacteria from nodules of alfalfa and sweet clover, grown at a site without a known history of cultivation, were identified as diverse genotypes of Ensifer, Rhizobium and Phyllobacterium species based on sequence analysis of ribosomal (16S and 23S rRNA) and protein-encoding (atpD and recA) genes, Southern hybridization/RFLP and a range of phenotypic characteristics. Among phage-resistant bacteria, one genotype of Rhizobium sp. predominated on alfalfa (frequency similar to 68%) but was recovered infrequently (similar to 1%) from sweet clover. A second genotype was isolated infrequently only from alfalfa. These genotypes fixed nitrogen poorly in association with sweet clover and Phaseolus vulgaris, but were moderately effective with alfalfa. They produced a near-neutral reaction on mineral salts agar containing mannitol, which is atypical of the genus Rhizobium. A single isolate of Ensifer sp. and two of Phyllobacterium sp. were recovered only from sweet clover. All were highly resistant to multiple antibiotics. Phylogenetic analysis indicated that Ensifer sp. strain T173 is closely related to, but separate from, the non-symbiotic species 'Sinorhizobium morelense'. Strain T173 is unique in that it possesses a 175 kb symbiotic plasmid and elicits ineffective nodules on alfalfa, sweet clover, Medicago lupulina and Macroptilium atropurpureum. The two Phyllobacterium spp. were non-symbiotic and probably represent bacterial opportunists. Three genotypes of E. meliloti that were symbiotically effective with alfalfa and sweet clover were encountered infrequently. Among phage-susceptible isolates, two genotypes of E. medicae were encountered infrequently and were highly effective with alfalfa, sweet clover and Medicago polymorpha. The ecological and practical implications of the findings are discusse