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Applied and Environmental Microbiology, January 2006, p. 628-637, Vol. 72, No. 1
0099-2240/06/$08.00+0     doi:10.1128/AEM.72.1.628-637.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Responses of the Anaerobic Bacterial Community to Addition of Organic C in Chromium(VI)- and Iron(III)-Amended Microcosms

Peter S. Kourtev,^1* Cindy H. Nakatsu,² and Allan Konopka¹

Department of Biological Sciences,¹ Department of Agronomy, Purdue University, West Lafayette, Indiana 47907²

Received 8 August 2005/ Accepted 1 November 2005

Chromium (VI) is toxic to microorganisms and can inhibit the biodegradation of organic pollutants in contaminated soils. We used microcosms amended with either glucose or protein (to drive bacterial community change) and Fe(III) (to stimulate iron-reducing bacteria) to study the effect of various concentrations of Cr(VI) on anaerobic bacterial communities. Microcosms were destructively sampled based on microbial activity (measured as evolution of CO₂) and analyzed for the following: (i) dominant bacterial community by PCR-denaturing gradient gel electrophoresis (DGGE) of the 16S rRNA gene; (ii) culturable Cr-resistant bacteria; and (iii) enrichment of iron-reducing bacteria of the Geobacteraceae family by real-time PCR. The addition of organic C stimulated the activities of anaerobic communities. Cr(VI) amendment resulted in lower rates of CO₂ production in glucose microcosms and a slow mineralization phase in protein-amended microcosms. Glucose and protein amendments selected for different bacterial communities. This selection was modified by the addition of Cr(VI), since some DGGE bands were intensified and new bands appeared in Cr(VI)-amended microcosms. A second dose of Cr(VI), added after the onset of activity, had a strong inhibitory effect when higher levels of Cr were added, indicating that the developing Cr-resistant communities had a relatively low tolerance threshold. Most of the isolated Cr-resistant bacteria were closely related to previously studied Cr-resistant anaerobes, such as Pantoea, Pseudomonas, and Enterobacter species. Geobacteraceae were not enriched during the incubation. The studied Cr(VI)-contaminated soil contained a viable anaerobic bacterial community; however, Cr(VI) altered its composition, which could affect the soil biodegradation potential.

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* Corresponding author. Mailing address: Department of Biological Sciences, 915 W. State Street, Purdue University, West Lafayette, IN 47907-2054. Phone: (765) 494-8145. Fax: (765) 494-0876. E-mail: pkourtev{at}purdue.edu

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Applied and Environmental Microbiology, January 2006, p. 628-637, Vol. 72, No. 1
0099-2240/06/$08.00+0     doi:10.1128/AEM.72.1.628-637.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Kourtev, P. S., Nakatsu, C. H., Konopka, A. (2009). Inhibition of Nitrate Reduction by Chromium(VI) in Anaerobic Soil Microcosms. Appl. Environ. Microbiol. 75: 6249-6257 [Abstract] [Full Text]