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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.

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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