Study of the involvement of lipopolysaccharides in the bacteria-plant biological nitrogen fixation

Nous nous sommes intéressés à la compréhension des mécanismes régissant la symbiose Rhizobium-Acacia dans les conditions de stress salin. Les lipopolysaccharides jouent un rôle important dans les étapes de cette symbiose. Le but était de mettre en évidence les modifications pariétales de la bactérie en réponse au stress salin par l’étude de la structure des lipopolysaccharides des souches isolées du désert marocain tolérant NaCl 7%. Ainsi, une nouvelle méthode d’hydrolyse des lipopolysaccharides sensible, non destructive et compatible avec la spectrométrie de masse a été développée. En présence de stress salin, nous avons montré que la membrane externe devenait plus hydrophobe en augmentant l’acylation de la région lipidique ainsi qu’en réduisant la présence des molécules de LPSs à longues chaînes de sucres.Des essais d’évaluation de l’efficience et de l’infectivité des Rhizobia étudiés ont été mis en œuvre pour déterminer l’impact de ces modifications des LPSs sur la symbiose sous stress salin.We were interested in the understanding of the mechanisms governing Rhizobium-Acacia symbiosis in salt stress conditions. Lipopolysaccharides play an important role in the stages of this symbiosis. The aim of this work was to highlight the changes occurring in the bacterial membrane in response to salt stress by studying the structure of the lipopolysaccharides isolated from Moroccan desert strains tolerating 7% NaCl. Thus, a new method of hydrolysis of the lipopolysaccharide - sensitive, non-destructive and compatible with mass spectrometry- was developed. We studied the LPSs strains grown with or without salt stress and we showed that in salt stress conditions, the outer membrane becomes more hydrophobic by increasing acylation of the lipid region and reducing the number of long sugar chains in LPSs. Tests for evaluating the efficiency and infectivity of the studied rhizobia were carried out to determine the impact of these LPS modifications on symbiosis under salt stress

Etude de l'implication des lipopolysaccharides dans la Symbiose Bactérie-Plante productrice d'azote

Nous nous sommes intéressés à la compréhension des mécanismes régissant la symbiose Rhizobium-Acacia dans les conditions de stress salin. Les lipopolysaccharides jouent un rôle important dans les étapes de cette symbiose. Le but était de mettre en évidence les modifications pariétales de la bactérie en réponse au stress salin par l étude de la structure des lipopolysaccharides des souches isolées du désert marocain tolérant NaCl 7%. Ainsi, une nouvelle méthode d hydrolyse des lipopolysaccharides sensible, non destructive et compatible avec la spectrométrie de masse a été développée. En présence de stress salin, nous avons montré que la membrane externe devenait plus hydrophobe en augmentant l acylation de la région lipidique ainsi qu en réduisant la présence des molécules de LPSs à longues chaînes de sucres.Des essais d évaluation de l efficience et de l infectivité des Rhizobia étudiés ont été mis en œuvre pour déterminer l impact de ces modifications des LPSs sur la symbiose sous stress salin.We were interested in the understanding of the mechanisms governing Rhizobium-Acacia symbiosis in salt stress conditions. Lipopolysaccharides play an important role in the stages of this symbiosis. The aim of this work was to highlight the changes occurring in the bacterial membrane in response to salt stress by studying the structure of the lipopolysaccharides isolated from Moroccan desert strains tolerating 7% NaCl. Thus, a new method of hydrolysis of the lipopolysaccharide - sensitive, non-destructive and compatible with mass spectrometry- was developed. We studied the LPSs strains grown with or without salt stress and we showed that in salt stress conditions, the outer membrane becomes more hydrophobic by increasing acylation of the lipid region and reducing the number of long sugar chains in LPSs. Tests for evaluating the efficiency and infectivity of the studied rhizobia were carried out to determine the impact of these LPS modifications on symbiosis under salt stress.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

A new rapid and micro-scale hydrolysis, using triethylamine citrate, for lipopolysaccharide characterization by mass spectrometry

Endotoxin (lipopolysaccharide, LPS) is, in general, composed of two moieties: a hydrophilic polysaccharide linked to a hydrophobic lipid A terminal unit and forms a major surface component of Gram-negative bacteria. The structural features of LPS moieties play a role in pathogenesis and also involve immunogenicity and diagnostic serology. The major toxic factor of LPS resides in the lipid A moiety, anchored in the outer layer of the bacterium, and its relative biological activity is critically related to fine structural features within the molecule. In establishing relationships between structural features and biological activities of LPS it is of the utmost importance to develop new analytical methods that can be applied to the complete unambiguous characterization of a specific LPS molecule. Herein is presented a practical rapid and sensitive analytical procedure for the mass spectral screening of LPS using triethylamine citrate as an agent for both disaggregation and mild hydrolysis of LPS. It provides improved matrix-assisted laser desorption/ionization (MALDI) mass spectra and, in particular, affords the identification of fragments retaining labile substituents present in the native macromolecular LPS structures. The methods were developed and applied using purified LPS of Escherichia coli and Salmonella enterica, as well as more complex LPS of Actnobacillus pleuropneumoniae. Copyright \ua9 2011 John Wiley & Sons, Ltd.Peer reviewed: YesNRC publication: Ye

Chemical investigation of Nigella sativa L. seed oil produced in Morocco

Seeds of Nigella sativa L. (black cumin or black seeds) are widely used in traditional Islamic medicine and for culinary purposes worldwide. Nigella seed oil is becoming popular in and out of the Islamic world. Composition of Nigella seed oil is known to be location-dependent. We investigated the composition of Nigella seed oil prepared by solvent- or cold press-extraction of Nigella seeds grown in Morocco. Oil extraction yield was 37% and 27% when solvent or cold press extraction methods were used, respectively. In terms of oil major components, composition of Nigella seed oil from Morocco is similar to that from other Mediterranean countries known for their Nigella seed-oil quality

Argan [Argania spinosa (L.) Skeels] oil

Argan oil is extracted from the kernels of Argania spinosa (L.) Skeels, a tree that almost exclusively grows endemically in southern Morocco. If argan oil was initia11y only known around its traditional production area, major efforts combining chemical, agronomic and human sciences have led to its international recognition and marketing. In addition, to ensure the sustainable production of a sufficient quantity of argan kernels, a vast and unprecedented program that led to the reforestation of large areas of drylands has been developed in Morocco. Therefore, argan oil production is considered as an economic and ecologic success. Edible argan oil is prepared by cold-pressing roasted argan kernels. Unroasted kernels afford an oil of cosmetic grade, showing a bitter taste. Both oils, which are not refined and are virgin oils, share a similar fatty acid content that includes oleic and linoleic acids as major components. Additiona11y, argan oil is rich in antioxidants. Together, these components likely contribute to the oil pharmacological properties that, in humans, traditionally included cardiovascular disease and skin protection. Recent scientific studies have greatly expanded the scope of these pharmacological activities. Argan oil is now rewarded with a "Geographic Indication" that certifies its exclusive and authentic Moroccan origin and the compliance with strict production rules. In addition, the quality of argan oil can nowadays be ascertained by using an array of physicochemica1 methods. By-products, generated in large quantity during argan oil production, are also finding promising development routes