Secondary Mineral Formation During Ferrihydrite Reduction by Shewanella oneidensis MR-1 Depends on Incubation Vessel Orientation and Resulting Gradients of Cells, Fe2+ and Fe Minerals

Urs Dippon, Caroline Schmidt, Sebastian Behrens, Andreas Kappler

    Research output: Contribution to journalArticlepeer-review

    17 Scopus citations

    Abstract

    In previous studies on microbial ferric iron (Fe(III)) reduction varying results regarding reduction rates and secondary mineral formation have been reported for almost identical conditions regarding temperature, pH, medium composition, Fe(III) mineral identity and bulk iron concentration. Here we show that in addition to physico-chemical parameters also geometric aspects, i.e., incubation orientation and dimension of cultivation vessels, influence the reduction rates and mineralogy. We incubated the Fe(III)-reducer Shewanella oneidensis MR-1 in test tubes at ferrihydrite (FH) concentrations of 1.3–50 mM either in vertical or horizontal orientation. Cells and minerals formed a pellet at the bottom of the tubes with different thicknesses at the same initial FH concentration depending on the incubation orientation. In vertically incubated tubes thick FH pellets were present at the bottom of the tubes and magnetite was formed in all setups with ≥2.5 mM initial FH. In tubes that were incubated horizontally no magnetite was formed in presence of <5 mM initial FH. Spatially resolved analysis of the supernatant and mineral sediment including voltammetric microelectrodes, Xray diffraction and Mössbauer spectroscopy revealed strong gradients of Fe2+ in both the aqueous supernatant and mineral pellets, whereas a heterogeneous distribution of cells and minerals in the sediment pellet was detected. The highest cell density and, consequently, the initiation of FH reduction was found at the mineral-supernatant interface. This study demonstrates that small changes in incubation conditions can significantly influence and even change the experimental results of geomicrobiological experiments.

    Original languageEnglish (US)
    Pages (from-to)878-889
    Number of pages12
    JournalGeomicrobiology Journal
    Volume32
    Issue number10
    DOIs
    StatePublished - Nov 26 2015

    Bibliographical note

    Publisher Copyright:
    © 2015, Copyright © Taylor & Francis Group, LLC.

    Keywords

    • biogenic magnetite formation
    • incubation conditions
    • microbial Fe(III) mineral reduction

    Fingerprint

    Dive into the research topics of 'Secondary Mineral Formation During Ferrihydrite Reduction by Shewanella oneidensis MR-1 Depends on Incubation Vessel Orientation and Resulting Gradients of Cells, Fe<sup>2+</sup> and Fe Minerals'. Together they form a unique fingerprint.

    Cite this