Mössbauer and EPR study of ferrihydrite and siderite biotransformations by a syntrophic culture of alkaliphilic bacteria

Abstract Transformations of iron-containing minerals − synthesized ferrihydrite and natural siderite performed by a syntrophic co-culture of Candidatus “Contubernalis alkalaceticum” and Geoalkalibacter ferrihydriticus in presence of ethanol as the substrate for the obligate syntroph – were studied by 57Fe Mossbauer and EPR spectroscopic techniques. Mossbauer spectra of solid phase samples were collected in the range of temperatures 5.5–300 K. X-band EPR studies were carried out at room temperature. The formation of a mixture of magnetite and maghemite, siderite and iron oxyhydroxycarbonate was found as the result of biogenic transformations of synthesized ferrihydrite. In the case of siderite, the formation of a mixture of magnetite and maghemite and iron oxyhydroxycarbonate was observed.