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Applied and Environmental Microbiology, January 2009, p. 468-473, Vol. 75, No. 2
0099-2240/09/$08.00+0     doi:10.1128/AEM.01817-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Microbial Iron Redox Cycling in a Circumneutral-pH Groundwater Seep{triangledown} ,{dagger}

Marco Blöthe and Eric E. Roden*

Department of Geology and Geophysics, University of Wisconsin, Madison, Wisconsin 53706

Received 6 August 2008/ Accepted 18 November 2008

The potential for microbially mediated redox cycling of iron (Fe) in a circumneutral-pH groundwater seep in north central Alabama was studied. Incubation of freshly collected seep material under anoxic conditions with acetate-lactate or H2 as an electron donor revealed the potential for rapid Fe(III) oxide reduction (ca. 700 to 2,000 µmol liter–1 day–1). Fe(III) reduction at lower but significant rates took place in unamended controls (ca. 300 µmol liter–1 day–1). Culture-based enumerations (most probable numbers [MPNs]) revealed significant numbers (102 to 106 cells ml–1) of organic carbon- and H2-oxidizing dissimilatory Fe(III)-reducing microorganisms. Three isolates with the ability to reduce Fe(III) oxides by dissimilatory or fermentative metabolism were obtained (Geobacter sp. strain IST-3, Shewanella sp. strain IST-21, and Bacillus sp. strain IST-38). MPN analysis also revealed the presence of microaerophilic Fe(II)-oxidizing microorganisms (103 to 105 cells ml–1). A 16S rRNA gene library from the iron seep was dominated by representatives of the Betaproteobacteria including Gallionella, Leptothrix, and Comamonas species. Aerobic Fe(II)-oxidizing Comamonas sp. strain IST-3 was isolated. The 16S rRNA gene sequence of this organism is 100% similar to the type strain of the betaproteobacterium Comamonas testosteroni (M11224). Testing of the type strain showed no Fe(II) oxidation. Collectively our results suggest that active microbial Fe redox cycling occurred within this habitat and support previous conceptual models for how microbial Fe oxidation and reduction can be coupled in surface and subsurface sedimentary environments.

* Corresponding author. Mailing address: Department of Geology and Geophysics, 1215 W. Dayton St., Madison, WI 53706. Phone: (608) 890-0724. Fax: (608) 262-0693. E-mail: eroden{at}geology.wisc.edu

{triangledown} Published ahead of print on 1 December 2008.

{dagger} Supplemental material for this article may be found at http://aem.asm.org/.

Applied and Environmental Microbiology, January 2009, p. 468-473, Vol. 75, No. 2
0099-2240/09/$08.00+0     doi:10.1128/AEM.01817-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Blothe, M., Roden, E. E. (2009). Composition and Activity of an Autotrophic Fe(II)-Oxidizing, Nitrate-Reducing Enrichment Culture. Appl. Environ. Microbiol. 75: 6937-6940 [Abstract] [Full Text]  


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