[Isolation and characterization of two strains of Streptomyces able to metabolize natural polysaccharides including mannan (author's transl)].

Two strains of aerobic and mesophilic microorganisms were isolated from palm-tree plantation sand. They grew on insoluble polysaccharides: mannan, cellulose, chitin as only source of carbon. This lytic activity was used for the purification of the two strains. The morphology of the organisms and the presence of LL-diaminopimetic acid in their cell-wall are characteristic of the genus Streptomyces. Investigations lead to: 1) the characterization of their specific polysaccharidase activity toward insoluble and natural beta-and alpha-glycans (mannan, cellulose, chitin, pectine and starch) and the formation of soluble saccharides (mannobiose, cellobiose, beta-D-N-acetylglucosamine, galacturonic acid, and maltose); 2) the research for antagonist, or synergic, effect on pathogenic bacteria and certain phytopathogenic microorganisms; only in the case of these latter was a weak lytic activity exerted by the two Streptomyces isolates, but one of them was shown to stimulate Colletotrichum lindemuthianum and Phialophora cinerescens; 3) a study of antibiotic sensitivity; the two strains were sensitive to tetracycline and streptomycin, but they had native resistance to other aminosides (gentamicin, kanamycin), to erythromycin and to the beta-lactam antibiotics (penicillin and cephalosporin); they possessed a beta-lactamase bound to the cell membrane.