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Applied and Environmental Microbiology, June 2004, p. 3475-3484, Vol. 70, No. 6
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.6.3475-3484.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Syntrophic-Methanogenic Associations along a Nutrient Gradient in the Florida Everglades

Ashvini Chauhan, Andrew Ogram,* and K. R. Reddy

Soil and Water Science Department, University of Florida, Gainesville, Florida 32611-0290

Received 30 October 2003/ Accepted 4 March 2004

Nutrient runoff from the Everglades Agricultural Area resulted in a well-documented gradient of phosphorus concentrations in soil and water, with concomitant ecosystem-level changes, in the northern Florida Everglades. It was recently reported that sulfate-reducing prokaryote assemblage composition, numbers, and activities are dependent on position along the gradient (H. Castro, K. R. Reddy, and A. Ogram, Appl. Environ. Microbiol. 68:6129-6137, 2002). The present study utilized a combination of culture- and non-culture-based approaches to study differences in composition of assemblages of syntrophic and methanogenic microbial communities in eutrophic, transition, and oligotrophic areas along the phosphorus gradient. Methanogenesis rates were much higher in eutrophic and transition regions, and sequence analysis of 16S rRNA gene clone libraries constructed from samples taken from these regions revealed differences in composition and activities of syntroph-methanogen consortia. Methanogens from eutrophic and transition regions were almost exclusively composed of hydrogenotrophic methanogens, with approximately 10,000-fold-greater most probable numbers of hydrogenotrophs than of acetotrophs. Most cultivable strains from eutrophic and transition regions clustered within novel lineages. In non-culture-based studies to enrich syntrophs, most bacterial and archaeal clones were either members of novel lineages or closely related to uncultivated environmental clones. Novel cultivable Methanosaeta sp. and fatty acid-oxidizing bacteria related to the genera Syntrophomonas and Syntrophobacter were observed in microcosms containing soil from eutrophic regions, and different lines of evidence indicated the existence of novel syntrophic association in eutrophic regions.


* Corresponding author. Mailing address: Soil and Water Science Department, University of Florida, P.O. Box 110290, Gainesville, FL 32611-0290. Phone: (352) 392-1951. Fax: (352) 392-3902. E-mail: avo{at}mail.ifas.ufl.edu.


Applied and Environmental Microbiology, June 2004, p. 3475-3484, Vol. 70, No. 6
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.6.3475-3484.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.




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