Mauran is an anionic, sulfated heteropolysaccharide with a high uronic-acid content, synthesized by strain S-30 of the halophilic bacterium Halomonas maura. Under optimum environmental and nutritional conditions, it is capable of producing up to 3.8 g of mauran per liter of medium. Aqueous solutions of mauran are highly viscous and display pseudoplastic, viscoelastic and thixotropic behavior. Its viscosity is stable over a wide pH range (3-11), after freezing-thawing processes, and in the presence of sucrose, salts, surfactants and alpha-hydroxyl acids. It has a high capacity for binding lead and other cations. Its molecular mass when collected from an MY medium supplemented with 2.5% w/v salt during the stationary growth phase is 4.7x10(6) Da.

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Calcium carbonate precipitation by 63 strains of moderately halophilic bacteria (Vibrio spp.) isolated from water of a saltern pond has been studied, taking into account the influence of salinity and temperature on the quantity and type of crystals precipitated. The bacteria formed crystals under all the conditions tested. All the crystals were magnesium calcite, with a variable Mg content, depending upon the medium provided. No aragonite was detected, even in a media with high Mg contents. Whether these microorganisms play an active role in precipitation is discussed, as well as the possibility that they may contribute to CaCO 3 precipitation in their natural habitats.

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