Substances bioactives élaborées par des cyanobactéries isolées de certains écosystèmes aquatiques marocains

Durant la saison chaude, plusieurs écosystèmes aquatiques (lacs, étangs, rivières, …) connaissent une croissance importante des cyanobactéries conduisant à la formation des efflorescences (blooms). Les cyanobactéries sont capables de produire une multitude de substances antimicrobiennes : antibactériennes, algicides, antifongique, antivirales et même des substances toxiques. L’objectif de ce travail constitue en l’étude des effets des substances bioactives produites par 10 souches de cyanobactéries isolées de certains écosystèmes aquatiques marocains. Ainsi, nous avons purifié et identifié les souches cyanobactéries isolées et nous avons testé l’activité de leurs substances extracellulaires et intracellulaires sur des micro-organismes d’intérêt sanitaire. Nous avons aussi évalué leur toxicité par le biotest souris. L’identification des 10 souches de cyanobactéries étudiées a montré qu’elles appartiennent à 3 familles à savoir les Oscillatoriaceae, les Nostocaceae et les Chroococcaceae. L’étude des effets des substances intracellulaires produites par ces souches de cyanobactéries, a montré que les extraits aqueux de ces substances ne donnent pas généralement une importante activité. Par contre, ces substances extraites par le méthanol inhibent la croissance de Micrococcus luteus et de Bacillus cereus. Les souches de cyanobactéries responsables de cette activité sont : Lyngbya sp., Pseudanabaena mucicola, Oscillatoria chlorina, Phormidium sp., Nostoc muscorum, Oscillatoria putrida et Microcystis aeruginosa. Les substances extracellulaires produites par les cyanobactéries étudiées ont aussi une activité antibactérienne vis-à-vis de M. luteus, Bacillus subtilis, Serratia marcescens, B. cereus, Escherichia coli 0128B12 et Staphylococcus aureus. Le biotest souris a permis de montrer que certaines cyanobactéries étudiées entraînent une mortalité des souris auxquelles sont injectées les cyanotoxines; ce qui montre que certaines souches de cyanobactéries produisent également des substances toxiques.Mots-clés : Activité antimicrobienne, cyanobactéries, écosystèmes aquatiques, substances extracellulaires, substances intracellulaires, toxicité

Portage rhinopharyngé de Streptococcus pneumoniae chez les enfants

Le rhinopharynx de l'enfant a une flore bactérienne résidante. C'est un écosystème complexe, comportant de nombreuses espèces bactériennes qui, d'une part, protègent en partie contre l'implantation de bactéries étrangères, et d'autre part, constituent le réservoir des bactéries impliquées dans les principales infections respiratoires, notamment les otites moyennes aiguës (OMA), et d’infections graves comme les bactériémies et les méningites. La majorité des enfants sont porteurs de Streptococcus pneumoniae à un moment ou autre de leur vie, mais ce dernier est plus important à l’âge préscolaire. L’objectif de ce travail est de faire la mise au point concernant S. pneumoniae à savoir le portage rhinopharyngé chez les enfants âgés de moins de deux ans, la prévalence, les facteurs de risque et l’impact du vaccin conjugué anti-pneumococcique sur l’incidence des infections invasives et sur la transmission et la dissémination des souches résistantes.Mots clés: Streptococcus pneumoniae, portage, résistance, vaccin anti-pneumococciqu

Activité insecticide d’une souche marocaine de Bacillus thuringiensis sur la mouche méditerranéenne : Ceratitis capitata (Wied.) (Diptera : Tephritidae)

Le présent travail consiste à étudier l’effet de deux types de toxines (δ -endotoxines et β -exotoxines) extraites à partir d’une souche de Bacillus thuringiensis (Bt A9) isolée d’un sol au Maroc sur la mouche Ceratitis capitata Wied (Diptera ; Tephritidae). les endotoxines de Bt A9 agissent sur la mortalité des larves et la longévité des adultes. par contre, les exotoxines présentent un effet notamment sur l’émergence des adultes. Les résultats de cette étude montrent que la souche Bt A9 présente une activité insecticide importante sur C. capitata. Les toxines de cette souche pourraient être utilisées dans la lutte biologique de cet insecte ravageur de plusieurs cultures fruitières au Maroc.Mots-clés : Bacillus thuringiensis, activité insecticide, ceratitis capitata,endotoxines, exotoxines

Role of rhizospheric microbiota as a bioremediation tool for the protection of soil-plant systems from microcystins phytotoxicity and mitigating toxin-related health risk

Frequent toxic cyanoblooms in eutrophic freshwaters produce various cyanotoxins such as the monocyclic heptapeptides microcystins (MCs), known as deleterious compounds to plant growth and human health. Recently, MCs are a recurrent worldwide sanitary problem in irrigation waters and farmland soils due to their transfer and accumulation in the edible tissues of vegetable produce. In such cases, studies about the persistence and removal of MCs in soil are scarce and not fully investigated. In this study, we carried out a greenhouse trial on two crop species: faba bean (Vicia faba var. Alfia 321) and common wheat (Triticum aestivum var. Achtar) that were grown in sterile (microorganism-free soil) and non-sterile (microorganism-rich soil) soils and subjected to MC-induced stress at 100 µg equivalent MC-LR L−1. The experimentation aimed to assess the prominent role of native rhizospheric microbiota in mitigating the phytotoxic impact of MCs on plant growth and reducing their accumulation in both soils and plant tissues. Moreover, we attempted to evaluate the health risk related to the consumption of MC-polluted plants for humans and cattle by determining the estimated daily intake (EDI) and health risk quotient (RQ) of MCs in these plants. Biodegradation was liable to be the main removal pathway of the toxin in the soil; and therefore, bulk soil (unplanted soil), as well as rhizospheric soil (planted soil), were used in this experiment to evaluate the accumulation of MCs in the presence and absence of microorganisms (sterile and non-sterile soils). The data obtained in this study showed that MCs had no significant effects on growth indicators of faba bean and common wheat plants in non-sterile soil as compared to the control group. In contrast, plants grown in sterile soil showed a significant decrease in growth parameters as compared to the control. These results suggest that MCs were highly bioavailable to the plants, resulting in severe growth impairments in the absence of native rhizospheric microbiota. Likewise, MCs were more accumulated in sterile soil and more bioconcentrated in root and shoot tissues of plants grown within when compared to non-sterile soil. Thereby, the EDI of MCs in plants grown in sterile soil was more beyond the tolerable daily intake recommended for both humans and cattle. The risk level was more pronounced in plants from the sterile soil than those from the non-sterile one. These findings suggest that microbial activity, eventually MC-biodegradation, is a crucial bioremediation tool to remove and prevent MCs from entering the agricultural food chain. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.This project has received funding from the European Union?s Horizon 2020 research and innovation program under the Marie Sk?odowska-Curie grant agreement No. 823860 and co-sup-ported by the strategical funding from FCT UIDB/04423/2020 and UIDP/04423/2020

Enzymes of the glutathione-ascorbate cycle in leaves and roots of rhizobia-inoculated faba bean plants (<em>Vicia faba</em> L.) under salinity stress.

Grain legumes such as the faba bean (Vicia faba L.) used for human as well as animal nutrition, are of great importance especially in countries under Mediterranean climate like Morocco, which is mainly characterized by semi-arid and arid climates and by saline soils. The objective of the present study was to evaluate the effects of salt stress on growth, nodulation and the enzymes of the glutathione ascorbate cycle of faba bean plants (Moroccan cultivar &quot;Aguadulce&quot;). The experiments were carried out under greenhouse-conditions, where faba bean plants were grown under control (nutrient solution) or salt stress conditions (nutrient solution containing 75 mM or 150 mM of NaCl). The activity of enzymes of the glutathione ascorbate cycle was studied in leaves and roots of faba bean plants inoculated by rhizobia RhOF4 or RhOF6, isolated from nodules of faba bean cultures in the region of Marrakech. The growth of faba bean plants decreased with increasing salt concentrations. Total weight and length of shoots significantly decreased under NaCl stress (p &lt; 0.05), especially at 150 mM. Also the nodulation of the roots was strongly decreased under salinity stress, with reductions of 91.35% and of 88.67% in the total nodule number of plants exposed to 150 mM of NaCl and inoculated by RhOF4 and by RhOF6 respectively. NaCl effects on the glutathione-ascorbate cycle were more pronounced in roots inoculated by RhOF6. Stress responding glutathione S-transferase (GST) activity was generally increased in roots inoculated by RhOF6 and submitted to salt stress. On the contrary, specific activities of glutathione peroxidase (GPOX), superoxide dismutase (SOD), ascorbate peroxidase (APOX) and monodehydroascorbate reductase (MDHAR) were reduced in roots of faba bean plants inoculated by RhOF6 exposed to saline treatment as compared to the controls. Our results show the importance of several enzymes of the ascorbate-glutathione cycle and the reduced glutathione (GSH) during some faba bean-rhizobia symbiotic combinations, in root defence and adaptation against salt stress conditions. (C) 2013 Elsevier Masson SAS. All rights reserved

Nodule phosphorus requirement and O-2 uptake in common bean genotypes under phosphorus deficiency

Acta Agric. Scand. Sect. B-Soil Plant Sci. ISI Document Delivery No.: 820FE Times Cited: 5 Cited Reference Count: 29 Bargaz, Adnane Drevon, Jean-Jacques Oufdou, Khalid Mandri, Btissam Faghire, Mustapha Ghoulam, Cherki Prad [06-08] This work was supported by PRAD project No 06-08. The authors wish to thank Michael Clairotte, Hesham Aslan Attar (INRA, Montpellier) for help in the N and P analysis, and Helene Vailhe (INRA, Montpellier) for her technical assistance. Taylor & francis as Oslo Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699International audienceThe effect of P deficiency on nodulation, nodule P content, nodule O-2 permeability and N fixation rates in Phaseolus vulgaris-rhizobia symbiosis was studied under glasshouse conditions. Four recombinant inbred lines (L34, L83, L115 and L147) and one variety cultivated in Morocco (Concesa) were inoculated with Rhizobium tropici CIAT 899 in hydroaeroponic culture. Two P levels i.e. 75 (deficient level) and 250 mu mol plant(-1) week(-1) P (sufficient level) were applied and the trial was assessed 42 days after transplanting that coincide with plant flowering stage. Under P-deficiency, decrease of plant growth (18%) and nodule biomass (19%) was detected and significantly pronounced in the sensitive line L147 compared with the remaining genotypes. Additionally, under P-deficiency, the efficiency in use of rhizobial symbiosis, estimated by the slope of the regression model of shoot biomass as a function of nodule biomass, was significantly increased in the four lines. This constraint did not significantly influence nodule P content in Concesa, but it was 24 and 41% lower in the tolerant and in the sensitive lines, respectively. Nodule P content was positively correlated to nodule biomass, r = 0.75, and shoot N, r = 0.92. These genotypic variations were associated with variability in nodule O-2 permeability that was significantly affected by the P level-bean genotype interaction. Under P-deficiency, nodule O-2 permeability was significantly reduced in the tested genotypes and accompanied with a decrease in shoot N content, especially in the sensitive lines (35%). Moreover, the ratios plant N fixed: nodule P content and plant N fixed: nodule dry weight were affected under P-deficiency in four lines with an exception observed in Concesa. Depending on the observed data we concluded that N-2 fixation efficiency could be influenced by nodulation and level of nodule P requirement which depend on both bean genotypes and P level

Occurrence, characterization and insecticidal activity of Bacillus thuringiensis strains isolated from argan fields in Morocco

Soils collected from five locations in the argan forest (an endemic plant) in Morocco were used to form the first collection of Bacillus thuringiensis (Bt) strains from this area (58 strains). Here we found that the argan forest is a major source of Bt, as 90.62% of the samples contained Bt strains. These strains produced mainly spherical or irregular crystals that in some cases remained adhered to the spore after cell lysis. There was no strain producing bipyramidal crystals, suggesting the absence of strains bearing cry1 genes. This was confirmed by PCR analysis using eight primer pairs that can potentially detect 13 different groups of cry and cyt genes. Strains containing cry7/8 were the most abundant (25.53%), followed by strains harbouring cry9A (14.89%), cry11 (8.51%) and cry4 (4.25%). The mixtures of spores and crystals as well as culture supernatants were assayed for toxicity towards Ceratitis capitata (Medfly), showing up to 30% mortality. Our findings suggest that the argan region is a suitable target for future and wider screening programmes looking for strains bearing toxins or combinations of them to develop more efficient Bt-based formulates

Identification at the species and symbiovar levels of strains nodulating Phaseolus vulgaris in saline soils of the Marrakech region (Morocco) and analysis of the otsA gene putatively involved in osmotolerance

9 páginas, 5 figuras, 1 tabla. -- The definitive version is available at http://www.elsevier.com/wps/find/journaldescription.cws_home/701801/descriptionSalinity is an increasing problem in Africa affecting rhizobia-legume symbioses. In Morocco, Phaseolus vulgaris is cultivated in saline soils and its symbiosis with rhizobia depends on the presence of osmotolerant strains in these soils. In this study, 32 osmotolerant rhizobial strains nodulating P. vulgaris were identified at the species and symbiovar levels by analysing core and symbiotic genes, respectively. The most abundant strains were closely related to Rhizobium etli and R. phaseoli and belonged to symbiovar phaseoli. A second group of strains was identified as R. gallicum sv gallicum. The remaining strains, identified as R. tropici, belonged to the CIAT 899T nodC group, which has not yet been described as a symbiovar. In representative strains, the otsA gene involved in the accumulation of trehalose and putatively in osmotolerance was analysed. The results showed that the phylogeny of this gene was not completely congruent with those of other core genes, since the genus Ensifer was more closely related to some Rhizobium species than others. Although the role of the otsA gene in osmotolerance is not well established, it can be a useful protein-coding gene for phylogenetic studies in the genus Rhizobium, since the phylogenies of otsA and other core genes are coincident at the species level.This research was funded by the AECID Spanish-Moroccan projects n◦A/018163/08 and A/025374/09, as well as the IFS project F/2826-3F. MF was supported by an AECID fellowship from the Spanish Ministry of External Affairs and Cooperation (MAEC). MHRB was the recipient of a JAE-Doc researcher contract from CSIC.Peer reviewe