title: XAS analysis of a nanostructured iron polysaccharide produced anaerobically by a strain of Klebsiella oxytoca.
abstract: A strain of Klebsiella oxytoca, isolated from acid pyrite-mine drainage, characteristically produces a ferric hydrogel, consisting of branched heptasaccharide repeating units exopolysaccharide (EPS), with metal content of 36 wt%. The high content of iron in the EPS matrix cannot be explained by a simple ferric ion bond to the sugar skeleton. The bio-generated Fe-EPS is investigated by X-ray absorption spectroscopy. Fe K-edge XANES analysis shows that iron is mostly in trivalent form, with a non-negligible amount of Fe(2+) in the structure. The Fe EXAFS results indicate that iron in the sample is in a mineralized form, prevalently in the form of nano-sized particles of iron oxides/hydroxides, most probably a mixture of different nano-crystalline forms. TEM shows that these nanoparticles are located in the interior of the EPS matrix, as in ferritin. The strain produces Fe-EPS to modulate Fe-ions uptake from the cytoplasm to avoid iron toxicity under anaerobic conditions. This microbial material is potentially applicable as iron regulator.
authors.affiliation: University of Nova Gorica, Vipavska 13, 5000, Nova Gorica, Slovenia. iztok.arcon@ung.si
authors.forename: Iztok
authors.initials: I
authors.lastname: Arčon
authors.forename: Oreste
authors.initials: O
authors.lastname: Piccolo
authors.forename: Stefano
authors.initials: S
authors.lastname: Paganelli
authors.forename: Franco
authors.initials: F
authors.lastname: Baldi
mesh_terms: D000693:Anaerobiosis; D007501:Iron / Q000737:chemistry* / Q000378:metabolism; D041121:Klebsiella oxytoca / Q000378:metabolism* / Q000648:ultrastructure; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D011135:Polysaccharides, Bacterial; D007501:Iron