3rd UF Water Institute Symposium Abstract

Submitter's Name Michelle Amit
Session Name Posters - Nutrient dynamics and enrichment impacts in aquatic ecosystems 2
Category Nutrient dynamics and enrichment impacts in aquatic ecosystems
Poster Number 44
Author(s) Michelle Amit,  Student (Presenting Author)
  Hee-Sung Bae,  UF - Soil and Water Science Department
  Andrew Ogram, UF - Soil and Water Science Department
  Syntrophic Acetate-Oxidizing Bacteria along a Nutrient Gradient in the Florida Everglades
  The Florida Everglades is historically limited in phosphorus; however, runoff from the Everglades Agricultural Area has resulted in a gradient in phosphorus concentrations running into the interior of the northern Everglades. Phosphorus enrichment resulted in a P- limitation along the gradient, such that a detailed understanding of the impacts of P-enrichment on the methanogenesis which has been recognized as an important final step in the carbon cycle. Syntrophic acetate-oxidation is one pathway for the production of methane, providing hydrogen to a hydrogen-utilizing methanogenic bacterial group. The ultimate objective of this study is to investigate the role(s) of syntrophic acetate-oxidizing bacteria (SAO) in soils along the nutrient gradient in Water Conservation Area 2-A, including a site previously exposed to high levels of nutrients (F1), a transition site (F4), and a site unimpacted by nutrient additions (U3). Previous studies tentatively identified the presence of SAO in these soils by PCR amplification of the gene encoding formyl tetrahydrofolate synthetase, common to all known SAO. In the current study, we identify SAO by using a combined approach of the cultivation and DNA-stable isotope probing with 13C-labled and unlabeled acetate. The Everglades sediment soils were incubated anaerobically with either 13C-labled or unlabeled acetate as sole carbon source and energy sources. Molecular cloning revealed that several different genera of Bacteria related to Clostridiales and yet uncultivated co-existed with hydrogen-utilizing methanogens in active methane producing enrichment cultures, suggesting that various SAO play an important role in the production of methane. An attempt is made to assay the SAO activity by measuring the ratio of 12C-labled methane to 13C-labeled methane in sediments supplemented 13C-labled acetate. The results obtained from this study will provide greater understanding of how SAO control methane production along nutrient gradients in the Everglades.