Résumé:
Lectins are ubiquitous proteins, non-immune origin, presenting several biological
properties, due to their unique ability to read the biological information codified in the threedimensional structure of sugars and glycoproteins. In this work, 6 strains of actinomycetes, which 5 belonging to rare genus were tested for their production of lectins. The hemagglutination test was used to select the strain Micromonospora aurantiaca GF 44c as best producing strain of these molecules. The study of the lectins contained in the intracellular fraction of strain Micromonospora aurantiaca GF44c led to the discovery of membrane vesicles of nanometric size similar to those found in other Gram-positive bacteria (30 to
100nm) through the use of different technical (FPLC Purification on Superose 6, transmission electron microscopy and dynamic light scattering). These vesicles have the ability to induce, in addition to hemagglutination, immunomodulatory and proteolytic activities. The SDSPAGE shows that these vesicles are very rich in diverse proteins. The proteomic analysis by mass spectrometry of these membrane vesicles identified 81 different proteins, mainly adhesins and membrane transporters (Substrate binding proteins and ABC transporters), enzymes (metalloprotease, peptidase, succinate dehydrogenase, Prolipoprotein diacylglyceryl transferase, DCSA oxidoreductase, Glutamine synthetase, N-acetylmuramoyl-L-alanine amidase), and lipoproteins. Functional analysis of these vesicular protein, suggest that these
vesicles play an important role in the survival of the bacterium in a stressful particular biological environment, by the nutrient acquisition (amino acids carbohydrates and inorganic ions), the resistance to stress factors through the action of several enzymes, and redirect the immune system of the host by a strong immunostimulation. This study describes for the first time the production of membrane vesicles in the genus Micromonospora, and the possible roles of these vesicles.
