This Article Full Text Full Text (PDF) Supplemental material Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Rowe, A. R. Articles by Richardson, R. E. Search for Related Content PubMed PubMed Citation Articles by Rowe, A. R. Articles by Richardson, R. E. Agricola Articles by Rowe, A. R. Articles by Richardson, R. E.

 Previous Article  |  Next Article 

Applied and Environmental Microbiology, November 2008, p. 6709-6719, Vol. 74, No. 21
0099-2240/08/$08.00+0     doi:10.1128/AEM.00445-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Characterization of the Community Structure of a Dechlorinating Mixed Culture and Comparisons of Gene Expression in Planktonic and Biofloc-Associated "Dehalococcoides" and Methanospirillum Species ^,

Annette R. Rowe,¹ Brendan J. Lazar,^2, Robert M. Morris,^2, and Ruth E. Richardson^2*

Field of Microbiology,¹ School of Civil and Environmental Engineering, Hollister Hall, Cornell University, Ithaca, New York 14853²

Received 23 February 2008/ Accepted 27 August 2008

This study sought to characterize bacterial and archaeal populations in a perchloroethene- and butyrate-fed enrichment culture containing hydrogen-consuming "Dehalococcoides ethenogenes" strain 195 and a Methanospirillum hungatei strain. Phylogenetic characterization of this microbial community was done via 16S rRNA gene clone library and gradient gel electrophoresis analyses. Fluorescence in situ hybridization was used to quantify populations of "Dehalococcoides" and Archaea and to examine the colocalization of these two groups within culture bioflocs. A technique for enrichment of planktonic and biofloc-associated biomass was developed and used to assess differences in population distribution and gene expression patterns following provision of substrate. On a per-milliliter-of-culture basis, most D. ethenogenes genes (the hydrogenase gene hupL; the highly expressed gene for an oxidoreductase of unknown function, fdhA; the RNA polymerase subunit gene rpoB; and the 16S rRNA gene) showed no statistical difference in expression between planktonic and biofloc enrichments at either time point studied (1 to 2 and 6 h postfeeding). Normalization of transcripts to ribosome (16S rRNA) levels supported that planktonic and biofloc-associated D. ethenogenes had similar gene expression profiles, with one notable exception; planktonic D. ethenogenes showed higher expression of tceA relative to biofloc-associated cells at 6 h postfeeding. These trends were compared to those for the hydrogen-consuming methanogen in the culture, M. hungatei. The vast majority of M. hungatei cells, ribosomes (16S rRNA), and transcripts of the hydrogenase gene mvrD and the housekeeping gene rpoE were observed in the biofloc enrichments. This suggests that, unlike the comparable activity of D. ethenogenes from both enrichments, planktonic M. hungatei is responsible for only a small fraction of the hydrogenotrophic methanogenesis in this culture.

---

* Corresponding author. Mailing address: 220 Hollister Hall, Cornell University, Ithaca, NY 14853. Phone: (607) 255-3233. Fax: (607) 255-9004. E-mail: rer26{at}cornell.edu

Published ahead of print on 5 September 2008.

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

Present address: TRC Environmental Corporation, 57 East Willow Street, Millburn, NJ 07041.

Present address: University of Washington, Center for Environmental Genomics, Seattle, WA 98105.

---

Applied and Environmental Microbiology, November 2008, p. 6709-6719, Vol. 74, No. 21
0099-2240/08/$08.00+0     doi:10.1128/AEM.00445-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.