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Ferrovum is a recently found new genus of acidophilic iron-oxidizing bacteria.Ferrovumspp. dominate the microbial community of a pilot plant for biological mine-water treatment and together with someGallionellarelatives appear to be key players of the process. Isolation ofFerrovumstrains should greatly be facilitated by a new APPW medium. Sequencing of the genome ofFerrovumsp. JA12 so far did not point to any alternative electron donors and also did not reveal genes for nitrogen fixation.

During the process of industrialization, the world-wide demand for resources steadily increases. Significant amounts of crucial metals and metalloids remain in low grade mineral deposits, however using conventional metal extraction methods on these minerals is not environmentally feasible. To overcome these problems, biohydrometallurgy has become the focus of recent research. Biohydrometallurgy utilizes the activity of iron-oxidizing bacteria to catalyze the dissolution of sulfide minerals, in our case local sphalerite (ZnS), with the aim of winning zinc and indium. To achieve this enrichment cultures originating from waters of the Reiche Zeche mine in Freiberg, Germany, were used as inoculum for two acidic growth media. To explore the efficiency of the bioleaching process leaching tests have been performed in shaking-flasks under laboratory conditions. Ground ore from Reiche Zeche is mainly comprised of the sulfide minerals sphalerite, galena and pyrite. After the leaching process both the solution and the residue were analyzed either by ICP-MS or XRD.The results clearly show that it is possible to leach indium and zinc from natural sphalerite, but that leaching efficiency is hindered, and dissolved indium removed, by the formation of iron-hydroxy precipitates. Hence, optimal conditions for maximum indium recovery with minimal precipitation have to be determined by variation of physico-chemical parameters. Furthermore, the microbial diversity of Reiche Zeche mine waters were studied with cultivation dependent and independent methods.

New acidophilic iron-oxidising bacteria like Ferrovum spp. and Gallionella relatives have recently been detected in several mine waters by culture-independent methods. To get information about their physiological characteristics, isolation of respective species is required. In former isolation studies, using a previously described iron-containing medium (iFeo) combined with the overlay-plate technique, mainly Acidithiobacillus ferrooxidans or A. ferrivorans had been obtained, although F. myxofaciens dominated the microbial community. Therefore, a new medium, called APPW was designed based on the water chemistry of a pilot plant for iron oxidation. The growth of iron-oxidising bacteria on overlay plates with iFeo and APPW media, respectively, was compared. Additionally, the iron, phosphate, and ammonium concentrations of APPW were separately adapted to iFeo. Colonies grown were analysed by PCR with primers specific for Ferrovum spp., Gallionella relatives, Acidithiobacillus spp., and Acidiphilium spp. While on all media most colonies obtained were contaminated by heterotrophic Acidiphilium spp., on iFeo Acidithiobacillus, as expected, turned out to be the dominating genus among the iron oxidisers. Interestingly on APPW and APPW-NH4Ferrovum dominated among the iron oxidisers. While APPW-Fe, as compared to APPW, seemed to inhibit the Gallionella relatives, APPW-PO4 resulted in an overall lower number of colonies, but a higher percentage of this taxon.

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