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Applied and Environmental Microbiology, February 2007, p. 680-690, Vol. 73, No. 3
0099-2240/07/$08.00+0     doi:10.1128/AEM.01519-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Correlation of Functional Instability and Community Dynamics in Denitrifying Dispersed-Growth Reactors

M. E. Gentile,^1* C. M. Jessup,² J. L. Nyman,³ and C. S. Criddle⁴

ARCADIS, San Francisco, California,¹ Department of Biological Sciences, Stanford University, Stanford, California,² Malcom Pirnie, Inc., Emeryville, California,³ Department of Civil and Environmental Engineering, Stanford University, Stanford, California⁴

Received 30 June 2006/ Accepted 16 November 2006

Understanding the relationship between microbial community dynamics and functional instability is an important step towards designing reliable biological water treatment systems. In this study, the community dynamics of two dispersed-growth denitrifying reactors were examined during periods of functional stability and instability. In both reactors during the period of functional instability, the effluent chemistry changed over time, with periods of high nitrate concentrations followed by periods of fluctuating nitrite concentrations. Community structure was examined by clone library analysis of the 16S rRNA gene. Community dynamics were investigated with terminal restriction fragment (T-RF) length polymorphism, and the functional diversity represented by T-RFs was assessed through nitrate reduction assays of representative isolates. During the period of functional instability, the community structure changed considerably, and the dynamics correlated significantly with effluent chemistry. The nitrite concentration was significantly correlated with the relative abundances of the nitrate-reducing Delftia- and Achromobacter-like T-RFs. The isolate representing the Acidovorax-like T-RF reduced nitrate directly to nitrogen in batch assays without the accumulation of any intermediates. The Acidovorax-like T-RF relative abundance was significantly negatively correlated with nitrite concentration, indicating that it was associated with good functional performance. The results of this study reveal a clear relationship between community dynamics and functional instability and the importance of diversity among nitrate-reducing populations within a denitrifying community.

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* Corresponding author. Mailing address: ARCADIS, 155 Montgomery St., Suite 1510, San Francisco, CA 94104. Phone: (510) 432-6251. Fax: (415) 374-2745. E-mail: mgentile{at}arcadis-us.com.

Published ahead of print on 1 December 2006.

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Applied and Environmental Microbiology, February 2007, p. 680-690, Vol. 73, No. 3
0099-2240/07/$08.00+0     doi:10.1128/AEM.01519-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

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