Different species of Bradyrhizobium from symbiovars genistearum and retamae nodulate the endemic Retama dasycarpa in the High Atlas Mountains

Retama dasycarpa is an endemic Retama species native to the cold semi-arid bioclimates of the High Atlas Mountains in Morocco. In this work, we analyzed the diversity of the microsymbionts nodulating this plant and their different phenotypic and symbiotic characteristics. Phylogenetic analysis of the 16S rRNA gene revealed that the tested isolates clustered in the Bradyrhizobium genus. Multilocus sequence analyses of four housekeeping genes (recA, gyrB, glnII and atpD) for 12 selected strains grouped them into four clusters close to B. lupini USDA 3051, B. frederickii CNPSo 3446, B. valentinum LmjM3 and B. retamae Ro19. The individual phylogenies of these core genes and the symbiotic genes nodC, nodA and nifH were congruent. These isolates showed a broad host range, being able to nodulate different legume hosts, such as R. sphaerocarpa, R. monosperma, Lupinus luteus, Cytisus grandiflorus and Chamaecytisus albidus, but not Phaseolus vulgaris or Glycine max. They all had a similar metabolic capacity, using the majority of the carbohydrates and amino acids tested as sole sources of carbon and nitrogen. Furthermore, out of the 12 selected strains, some displayed plant growth-promoting features, with six of them solubilizing phosphate and three of them producing siderophores. The present work provides, for the first time, a detailed description about the microsymbionts associated with the endemic legume R. dasycarpa.This work was supported by the Ministry of Higher Education and Innovation. Dr Mouad Lamrabet was granted a fellowship from the PPR2-BIOMIVER project. The authors want to thank all the people who contributed to this work

Structural Basis and Catalytic Mechanism for the Dual Functional Endo-β-N-Acetylglucosaminidase A

Endo-β-N-acetylglucosaminidases (ENGases) are dual specificity enzymes with an ability to catalyze hydrolysis and transglycosylation reactions. Recently, these enzymes have become the focus of intense research because of their potential for synthesis of glycopeptides. We have determined the 3D structures of an ENGase from Arthrobacter protophormiae (Endo-A) in 3 forms, one in native form, one in complex with Man3GlcNAc-thiazoline and another in complex with GlcNAc-Asn. The carbohydrate moiety sits above the TIM-barrel in a cleft region surrounded by aromatic residues. The conserved essential catalytic residues – E173, N171 and Y205 are within hydrogen bonding distance of the substrate. W216 and W244 regulate access to the active site during transglycosylation by serving as “gate-keepers”. Interestingly, Y299F mutation resulted in a 3 fold increase in the transglycosylation activity. The structure provides insights into the catalytic mechanism of GH85 family of glycoside hydrolases at molecular level and could assist rational engineering of ENGases

Purification and characterization of an endo-N-acetyl-beta-D-glucosaminidase from the culture medium of Stigmatella aurantiaca DW4.

A novel endo-N-acetyl-beta-D-glucosaminidase (ENGase), acting on the di-N-acetylchitobiosyl part of N-linked glycans, was characterized in the culture medium of Stigmatella aurantiaca DW4. Purified to homogeneity by ammonium sulfate precipitation, gel filtration, and chromatofocusing, this ENGase presents, upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis, a molecular mass near 27 kDa. Optimal pH and pI were 4.0 and 6.8, respectively. The enzyme, named ENGase St, exhibits high activity on oligomannoside-type glycoasparagines and glycoproteins and could also hydrolyze hybrid- and complex-type glycoasparagines but does not acts as a murein hydrolase

Functional profiles of soil microbial populations under various climatic conditions and agricultural practices in Burkina-Faso

International audienceBIOSOL is a multidisciplinary scientific program (soil science, agronomy, geography) which aims at understanding and promoting agro-ecological practices among peasant communities in Burkina-Faso. In this work, the pedological, geochemical and microbiological characteristics of agricultural soils were investigated in order to make an inventory of soil fertility. Two sites (villages of Sampiéri and Bandougou) with contrasted pedo-climatic conditions were selected

Biochar, Ochre, and Manure Maturation in an Acidic Technosol Helps Stabilize As and Pb in Soil and Allows Its Vegetation by Salix triandra

Past mining extraction activities still have a negative impact in the present time, the resulting metal(loid) contaminated soils affecting both the environment and human health. Assisted phytostabilization technology, combining soil conditioner application to immobilize metal(loid)s and plant growth to reduce erosion and leaching risks, is a useful strategy in the restoration of metal(loid) contaminated lands. However, contaminants will respond differently to a particular amendment, having their own specific characteristics. Therefore, in multi-contaminated soils, soil conditioner combination has been suggested as a good strategy for metal(loid) immobilization. In the present study, in a mesocosm experiment, organic (biochar and manure) and inorganic (ochre) amendments were evaluated in single and combined applications for their effect on metal(loid) stabilization and Salix triandra growth improvement, in an arsenic and lead highly contaminated soil. Specifically, the effects of these amendments on soil properties, metal(loid) behavior, and plant growth were evaluated after they aged in the soil for 6 months. Results showed that all amendments, except biochar alone, could reduce soil acidity, with the best outcomes obtained with the three amendments combined. The combination of the three soil conditioners has also led to reducing soil lead availability. However, only ochre, alone or combined with the other soil fertilizers, was capable of immobilizing arsenic. Moreover, amendment application enhanced plant growth, without affecting arsenic accumulation. On the contrary, plants grown on all the amended soils, except plants grown on soil added with manure alone, showed higher lead concentration in leaves, which poses a risk of return of lead into the soil when leaves will shed in autumn. Considering that the best plant growth improvement, together with the lowest increase in lead aerial accumulation, was observed in manure-treated soil, the addition of manure seems to have potential in the restoration of arsenic and lead contaminated soil