A bacterium isolated from microbial mats located on a polynesian atoll produced a high molecular weight (3,000 kDa) and highly sulphated exopolysaccharide. Previous studies showed that the chemical structure of this EPS consisted of neutral sugars, uronic acids, and high proportions of acetate and sulphate groups. The copper- and iron-binding ability of the purified pre-treated native EPS was investigated. Results showed that this EPS had a very high affinity for both copper (9.84 mmol g(-1) EPS) and ferrous iron (6.9 mmol g(-1) EPS). Amazingly, this EPS did not show any affinity for either ferric ions or selenium salts. This finding is one of the first steps in assessing the biotechnological potential of this polysaccharide.