A Klebsiella oxytoca strain BAS-10 was isolated from pyrite mine drainages. This enterobacter ferments Fe(III)-citrate and Na(I)-citrate. Physiological studies on a relative species K. pneumoniae and Salmonella typhimurium growing on Na(I)-citrate by fermentative metabolism have been already reported. These strains grow on citrate by Na(I)-dependent pathway, forming acetic acid and CO2 as final metabolites. Moreover strain BAS-10 differs from other Klebsiella sp. and other citrate fermenting bacteria that it thrives on high concentrations of Fe(III)-citrate and produces at the stationary phase a thick iron gel. This characteristic is due to the fact that strain BAS-10 synthesizes a branched acid exopolysaccharides (ESP) constituted by the following heptasaccharide: 2)-α-Rha-(13)-β-Gal-(12)-α-Rha-(14)-β-GlcA-[β-GlcA-(14)]-(13)-α-Rha-(13)-α-Rha-(1(2). Recently a regulatory network was disclosed by proteomic analyses of iron-dependent cell processes of Fe(III)-citrate fermentation (3). This wild strain, adapted to mine drainages, copes with iron and other heavy metal toxicity by complexing them outside with EPS. Different metal-EPS had been prepared for nutraceutical, catalysis reactions and antibiotic properties depending on the metal linked to the EPS.