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

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bTo gain insight into the mechanisms controlling methanogenic pathways in the Florida Everglades, the distribution and functional activities of methanogens and sulfate-reducing prokaryotes (SRPs) were investigated in soils (0 to 2 or 0 to 4 cm depth) across the well-documented nutrient gradient in the water conservation areas (WCAs) caused by runoff from the adjacent Everglades Agricultural Area. The methyl coenzyme M reductase gene (mcrA) sequences that were retrieved from WCA-2A, an area with relatively high concentrations of SO 4 2؊ (>39 M), indicated that methanogens inhabiting this area were broadly distributed within the orders Methanomicrobiales, Methanosarcinales, Methanocellales, Methanobacteriales, and Methanomassiliicoccales. In more than 3 years of monitoring, quantitative PCR (qPCR) using newly designed group-specific primers revealed that the hydrogenotrophic Methanomicrobiales were more numerous than the Methanosaetaceae obligatory acetotrophs in SO 4 2؊ -rich areas of WCA-2A, while the Methanosaetaceae were dominant over the Methanomicrobiales in WCA-3A (with relatively low SO 4 2؊ concentrations; <4 M). qPCR of dsrB sequences also indicated that SRPs are present at greater numbers than methanogens in the WCAs. In an incubation study with WCA-2A soils, addition of MoO 4 2؊ (a specific inhibitor of SRP activity) resulted in increased methane production rates, lower apparent fractionation factors [␣ app ; defined as (amount of ␦ 13 CO 2 ؉ 1,000)/ (amount of ␦ 13 CH 4 ؉ 1,000)], and higher Methanosaetaceae mcrA transcript levels compared to those for the controls without MoO 4 2؊ . These results indicate that SRPs play crucial roles in controlling methanogenic pathways and in shaping the structures of methanogen assemblages as a function of position along the nutrient gradient.

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confidence: 99%

Distribution, Activities, and Interactions of Methanogens and Sulfate-Reducing Prokaryotes in the Florida Everglades

Bae

Holmes

Chanton

et al. 2015

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“…We previously reported differences in microbial assemblages of sulfate-reducing prokaryotes and methanogens in Everglades soils (7,9,10). Dissimilatory sulfite reductase (dsrA) clone libraries constructed from DNA taken from soils of eutrophic regions were dominated by Desulfotomaculum-like sequences related to those species capable of complete oxidation of organic substrates.…”

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confidence: 99%

Distribution and Stability of Sulfate-Reducing Prokaryotic and Hydrogenotrophic Methanogenic Assemblages in Nutrient-Impacted Regions of the Florida Everglades

Castro¹,

Newman

Reddy³

et al. 2005

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Although the influence of phosphorus loading on the Everglades ecosystem has received a great deal of attention, most research has targeted macro indicators, such as those based on vegetation or fauna, or chemical and physical parameters involved in biogeochemical cycles. Fewer studies have addressed the role of microorganisms, and these have mainly targeted gross informative parameters such as microbial biomass, enzymatic activities, and microbial enumerations. The objectives of this study were to characterize the dynamics of sulfate-reducing and methanogenic assemblages using terminal restriction fragment length polymorphism (T-RFLP) targeting the dissimilatory sulfite reductase (dsrA) and methyl coenzyme M reductase (mcrA) genes, respectively, and assess the impact of nutrient enrichment on microbial assemblages in the northern Everglades. T-RFLP combined with principal component analysis was a powerful technique to discriminate between soils from sites with eutrophic, transitional, and oligotrophic nutrient concentrations. dsrA T-RFLP provided a higher level of discrimination between the three sites. mcrA was a relatively weaker system to distinguish between sites, since it could not categorically discriminate between eutrophic and transition soil samples, but may be useful as an early indicator of phosphorus loading which is altering hydrogenotrophic methanogenic community in the transition zones, making them more similar to eutrophic zones. Clearly, targeting a combination of different microbial communities provides greater insight into the functioning of this ecosystem and provides useful information for understanding the relationship between eutrophication effects and microbial assemblages.

“…in sloughs to dense stands of cattail (Typha domingensis Pers.). Significantly greater primary productivity in eutrophic regions resulted in greater carbon input to the soils, leading to greater peat accumulation (2,27,37) and higher rates of methanogenesis and anaerobic respiration (4)(5)(6)(7). Concomitant with larger amounts of available carbon in eutrophic regions are changes in the composition and increases in the sizes of specific microbial groups responsible for carbon cycling, such as methanogens, fermenters, and sulfate-reducing prokaryotes (SRP) (4-7, 14, 37; I. Uz and A. Ogram, submitted for publication).…”

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confidence: 99%

Fatty Acid-Oxidizing Consortia along a Nutrient Gradient in the Florida Everglades

Chauhan

Ogram

2006

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The Florida Everglades is one of the largest freshwater marshes in North America and has been subject to eutrophication for decades. A gradient in P concentrations extends for several kilometers into the interior of the northern regions of the marsh, and the structure and function of soil microbial communities vary along the gradient. In this study, stable isotope probing was employed to investigate the fate of carbon from the fermentation products propionate and butyrate in soils from three sites along the nutrient gradient. For propionate microcosms, 16S rRNA gene clone libraries from eutrophic and transition sites were dominated by sequences related to previously described propionate oxidizers, such as Pelotomaculum spp. and Syntrophobacter spp. Significant representation was also observed for sequences related to Smithella propionica, which dismutates propionate to butyrate. Sequences of dominant phylotypes from oligotrophic samples did not cluster with known syntrophs but with sulfate-reducing prokaryotes (SRP) and Pelobacter spp. In butyrate microcosms, sequences clustering with Syntrophospora spp. and Syntrophomonas spp. dominated eutrophic microcosms, and sequences related to Pelospora dominated the transition microcosm. Sequences related to Pelospora spp. and SRP dominated clone libraries from oligotrophic microcosms. Sequences from diverse bacterial phyla and primary fermenters were also present in most libraries. Archaeal sequences from eutrophic microcosms included sequences characteristic of Methanomicrobiaceae, Methanospirillaceae, and Methanosaetaceae. Oligotrophic microcosms were dominated by acetotrophs, including sequences related to Methanosarcina, suggesting accumulation of acetate.