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Iron-oxidizing bacteria in heavy metal-contaminated creeks



Institute of Ecology
Limnology/Aquatic Geomicrobiology
Dornburger Str. 159
07743 Jena
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Telephone: +49 (0)3641/9-49465
Fax: +49 (0)3641/9-49402

Maria Fabisch


Iron exists either as oxidized ferric [Fe(III)] or as reduced ferrous [Fe(II)] iron, in dissolved form or as part of iron-bearing minerals. Iron redox transformations can be caused by both chemical and microbial processes. Microbial oxidation of Fe(II) can be coupled to the reduction of e.g., oxygen (aerobic or microaerobic iron oxidizing microorganisms [FeOM]). Under oxic, pH neutral conditions, FeOM have to compete with fast abiotic Fe(II) oxidation in contrast to the low competition under acidic or micro-/anoxic conditions. Ferric iron precipitates as Fe(III) oxides/hydroxides due to low solubility under slightly acidic and pH neutral conditions and can be used as electron acceptor under anoxic conditions by Fe(III) reducers [FeRM].

Fe(III) oxyhydroxides can co-precipitate or adsorb dissolved heavy metals and lower their bioavailability. Thus, FeOM could be useful for remediation in heavy metal contaminated environments. However, little information is available on the diversity and heavy metal tolerance of FeOM living under slightly acidic pH, while acidophilic FeOM are well-known to tolerate high heavy metal concentrations: Acidithiobacillus ferrooxidans is metabolically active at concentrations of 800 mM Cu(II), 500 mM Cd(II), 1000 mM Ni(II) and 1071 mM Zn(II) (Dopson et al. 2003 Microbiology 149).


In the former uranium-mining district near Ronneburg, Thuringia, Germany, acid mine drainage-impacted creeks show the accumulation of Fe(III) precipitates. This project aimed to elucidate the contribution of FeOM to the sedimentation of heavy metals in creeks in this area, which contain upcoming contaminated ground and seepage waters. The objectives were to characterize the geochemistry of the field site and the distribution of heavy metals in waters and sediments, to evaluate the potential for microbial Fe(II) oxidation and Fe(III) reduction, and to investigate the microbial iron oxidizer and reducer communities under different pH and oxygen conditions.

The Gessenbach creek was detected to contain highly metal-enriched sediments. Metals like zink and copper were mainly bound to the iron oxide fraction in sediments, as shown by sequential extractions. A high heavy metal tolerance of neutrophilic/acidotolerant microaerobic FeOM from Gessenbach sediment was demonstrated. Gallionella spp.-related bacteria  were identified to be the dominant FeOM in metal-contaminated ground and creek water.


Fabisch M, Freyer G, Johnson CA, Büchel G, Akob DM, Neu TR, Küsel K (2015) Dominance of 'Gallionella capsiferriformans' and heavy metal association with Gallionella-like stalks in metal-rich pH 6 mine water discharge. Geobiology. doi: 10.1111/gbi.12162

Johnson CA, Freyer G, Fabisch M, Caraballo MA, Küsel K, Hochella Jr MF (2014) Observations and assessment of iron oxide and green rust nanoparticles in metal-polluted mine drainage within a steep redox gradient. Environmental Chemistry 11: 377-391. doi: 10.1071/EN13184

Fabisch M, Beulig F, Akob DM and Küsel K (2013) Surprising abundance of Gallionella-related iron oxidizers in creek sediments at pH 4.4 or at high heavy metal concentrations. Frontiers in Microbiology 4: 390. doi: 10.3389/fmicb.2013.00390


Iron-rich sediment in the Gessenbach Creek

(photo: Maria Fabisch, 2009).

Sediment terraces at the creek bank

(photo: Felix Beulig, 2011).

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