PRODUCTION AND CHARACTERIZATION OF AN EXOPOLYSACCHARIDE EXCRETED BY ADEEP-SEA HYDROTHERMAL VENT BACTERIUM ISOLATED FROM THE POLYCHAETE ANNELID ALVINELLA-POMPEJANA

The heterotrophic and mesophilic marine bacterium HYD-1545 was isolate d on a metal-amended medium from the dorsal integument of the hydrothe rmal vent polychaete Alvinella pompejana. This strain, which can be as signed to the genus Alteromonas on the basis of its G+C content and ph enotypical features, produced large amounts of an acidic polysaccharid e in batch cultures. The polysaccharide was excreted during the statio nary phase of growth and contained glucose, galactose, glucuronic acid , galacturonic acid, and 4,6-O-(1-carboxyethilidene)-galactose as majo r components. This polysaccharide was a polyelectrolyte, and the visco sity of its solutions depended on the ionic strength. The decrease in viscosity with increasing NaCl concentrations and the effect of Ca2+ i n decreasing the viscosity at low Ca2+ concentrations support a model in which the polysaccharide carries anionic groups. However, an unusua l behavior was observed at higher concentrations and could be related to intermolecular interactions involving Ca2+ ions.