Morphological and biochemical characterization of the exocellular investments of polysaccharide-producing Nostoc strains from the Pasteur Culture Collection |
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Authors: | De Philippis Roberto Faraloni Cecilia Margheri Maria C Sili Claudio Herdman Michael Vincenzini Massimo |
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Institution: | (1) Dipartimento di Biotecnologie Agrarie, Universita' degli Studi di Firenze, Italy;(2) Centro di Studio dei Microrganismi Autotrofi, CNR, Firenze, Italy;(3) Unitè de Physiologie Microbienne (CNRS URA 2172), Département de Biochimie et Génétique Moléculaire, Institut Pasteur, Paris, France |
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Abstract: | A total of 40 Nostoc strains, belonging to the Pasteur Culture Collection and originally isolated from different habitats, were photoautotrophically
grown in liquid cultures and tested for the presence of exocellular polysaccharidic investments surrounding the trichomes.
However, 25 of them showed a significant presence of these structures, coupled with the release of polysaccharidic material
(RPS) into the medium. A rather large number of different morphological forms was observed in the cultures during growth,
but at the time of harvesting the predominant morphological form was, in most cases, the vegetative trichome. With regard
to the exocellular mucilaginous investments, three main types of morphologies were observed: (i) capsules surrounded by an
external pellicle, (ii) capsules with sharp outlines but without an external pellicle, (iii) slimy investments that either
loosely surrounded the trichomes without following their shape or were organized in large globular lumps. Among the twenty-five
strains that released polysaccharides into the culture medium, three showed mean daily productivities ranging from 30 to 50
mg (RPS) l−1 d−1, values comparable with those of the most productive cyanobacterial strains so far described. The morphological characteristics
of the polysaccharidic investments produced by the Nostoc strains seem not to be related to their original habitats. Furthermore, the differences in RPS productivities observed among
the strains seem not to be related to the shape of the mucilaginous exocellular investments. Chemical analysis of purified
samples of the polysaccharides demonstrated that all the polymers possess an acidic nature, due to the presence of uronic
acids, and that they are characterized by the presence of a peptidic moiety and of amino sugars.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | Exocellular investments exopolysaccharide morphology Nostoc Pasteur Culture Collection |
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