Microbial ecology of anaerobic terminal carbon mineralization in Everglades soils, with emphasis on sulfate-reducing prokaryotic assemblages

In freshwater wetlands, physical and chemical parameters affect the microbial communities responsible for the carbon and sulfur cycles. Due to the metabolic and physiological versatility of sulfate-reducing prokaryotes (SRP), changes in this microbial community would reflect changes at the process level in the Everglades wetlands. This study was conducted in three sites in the Everglades Water Conservation Area 2A, with different levels of eutrophication due to phosphorus loading.; Most-probable-number enumerations showed that SRP were present in higher numbers, more active and more metabolically diverse in eutrophic regions of the marshes. Diversity within dissimilatory sulfite reductase (dsr ) genes was found in eutrophic and pristine regions of the marshes. Significantly, Desulfotomaculum-like sequences from eutrophic regions were related to those Desulfotomaculum able to carry out complete oxidation. In pristine regions, they were related to those unable to carry out complete oxidation. Molecular techniques revealed that nutrient loading resulted in a selection of different SRP communities.; Culture-independent techniques targeting the archaeal 16S rRNA and methyl coenzyme M reductase (mcr) genes of methanogens revealed a dominance of sequences related to Methanomicrobiales, suggesting that hydrogen plays a major role in methanogenesis.; Everglades WCA-2A is a case where hydrogen is an important methanogenic precursor, and acetate is not the main methanogenic precursor. Hydrogen regulates the fermentation process, shifting the fermentation product proportion, favoring the production of fatty acids and suppressing the production of acetate. The results from dsr terminal restriction fragment length polymorphism (T-RFLP) analyses were useful to distinguish between three sites with different levels of impact, but the mcr T-RFLP may indicate that phosphorus loading is altering the methanogenic community in the transition zones, making them more similar to eutrophic zones. The shift revealed by mcr T-RFLP may be an early indication of phosphorus impact in southern WCA-2A. Clearly, targeting a combination of different microbial communities provides greater insight into the functioning of this ecosystem, as well as providing useful information for planning and implementing ecosystem restoration technologies.