Abstract: A method includes administering a cosmetically or dermopharmaceutically effective quantity of exopolysaccharide of a bacterial strain isolated from Pseudoalteromonas sp. with deposit number CNCM I-4150 to at least one of skin, mucous membranes, hair and nails for the treatment and/or care of the skin, mucous membranes, hair and/or nails, and cosmetic and/or dermopharmaceutical compositions including the exopolysaccharide. In particular, the method and composition are suited to treatment of the aging of skin and for the treatment and/or care of disorders, conditions and/or diseases which are a result of a lack or decrease in hydration.