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Phototrophic Fe(II)-oxidation in the chemocline of a ferruginous meromictic lake

Miracle, Maria R.; Walter, Xavier Alexis; Picazo, Antonio; Vicente, Eduardo; Camacho, Antonio; Aragno, Michel; Zopfi, Jakob

Authors

Maria R. Miracle

Antonio Picazo

Eduardo Vicente

Antonio Camacho

Michel Aragno

Jakob Zopfi



Abstract

© 2014 Walter, Picazo, Miracle, Vicente, Camacho, Aragno and Zopfi. Precambrian Banded Iron Formation (BIF) deposition was conventionally attributed to the precipitation of iron-oxides resulting from the abiotic reaction of ferrous iron (Fe(II)) with photosynthetically produced oxygen. Earliest traces of oxygen date from 2.7 Ga, thus raising questions as to what may have caused BIF precipitation before oxygenic photosynthesis evolved. The discovery of anoxygenic phototrophic bacteria thriving through the oxidation of Fe(II) has provided support for a biological origin for some BIFs, but despite reports suggesting that anoxygenic phototrophs may oxidize Fe(II) in the environment, a model ecosystem of an ancient ocean where they are demonstrably active was lacking. Here we show that anoxygenic phototrophic bacteria contribute to Fe(II) oxidation in the water column of the ferruginous sulfate-poor, meromictic lake La Cruz (Spain). We observed in-situ photoferrotrophic activity through stimulation of phototrophic carbon uptake in the presence of Fe(II), and determined light-dependent Fe(II)-oxidation by the natural chemocline microbiota. Moreover, a photoferrotrophic bacterium most closely related to Chlorobium ferrooxidans was enriched from the ferruginous water column. Our study for the first time demonstrates a direct link between anoxygenic photoferrotrophy and the anoxic precipitation of Fe(III)-oxides in a ferruginous water column, providing a plausible mechanism for the bacterial origin of BIFs before the advent of free oxygen. However, photoferrotrophs represent only a minor fraction of the anoxygenic phototrophic community with the majority apparently thriving by sulfur cycling, despite the very low sulfur content in the ferruginous chemocline of Lake La Cruz.

Journal Article Type Article
Publication Date Jan 1, 2014
Journal Frontiers in Microbiology
Print ISSN 1664-302X
Electronic ISSN 1664-302X
Publisher Frontiers Media
Peer Reviewed Peer Reviewed
Volume 5
Issue DEC
APA6 Citation Miracle, M. R., Walter, X. A., Walter, X. A., Picazo, A., Miracle, M., Vicente, E., …Zopfi, J. (2014). Phototrophic Fe(II)-oxidation in the chemocline of a ferruginous meromictic lake. Frontiers in Microbiology, 5(DEC), https://doi.org/10.3389/fmicb.2014.00713
DOI https://doi.org/10.3389/fmicb.2014.00713
Keywords geomicrobiology, anoxygenic photosynthesis, early life evolution, banded iron formation, cryptic sulfur cycling
Publisher URL http://dx.doi.org/10.3389/fmicb.2014.00713
Related Public URLs http://www.frontiersin.org/Aquatic_Microbiology?field=Microbiology

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