Composition and Function of Sulfate-Reducing Prokaryotes in Eutrophic and Pristine Areas of the Florida Everglades

Abstract

As a result of agricultural activities in regions adjacent to the northern boundary of the Florida Everglades, a nutrient gradient developed that resulted in physicochemical and ecological changes from the original system. Sulfate input from agricultural runoff and groundwater is present in soils of the Northern Everglades, and sulfate-reducing prokaryotes (SRP) may play an important role in biogeochemical processes such as carbon cycling. The goal of this project was to utilize culture-based and non-culture-based approaches to study differences between the composition of assemblages of SRP in eutrophic and pristine areas of the Everglades. Sulfate reduction rates and most-probable-number enumerations revealed SRP populations and activities to be greater in eutrophic zones than in more pristine soils. In eutrophic regions, methanogenesis rates were higher, the addition of acetate stimulated methanogenesis, and SRP able to utilize acetate competed to a limited degree with acetoclastic methanogens. A surprising amount of diversity within clone libraries of PCR-amplified dissimilatory sulfite reductase (DSR) genes was observed, and the majority of DSR sequences were associated with gram-positive spore-forming Desulfotomaculum and uncultured microorganisms. Sequences associated with Desulfotomaculum fall into two categories: in the eutrophic regions, 94.7% of the sequences related to Desulfotomaculum were associated with those able to completely oxidize substrates, and in samples from pristine regions, all Desulfotomaculum-like sequences were related to incomplete oxidizers. This metabolic selection may be linked to the types of substrates that Desulfotomaculum spp. utilize; it may be that complete oxidizers are more versatile and likelier to proliferate in nutrient-rich zones of the Everglades. Desulfotomaculum incomplete oxidizers may outcompete complete oxidizers for substrates such as hydrogen in pristine zones where diverse carbon sources are less available.

Linkage between community diversity of sulfate-reducing microorganisms and methylmercury concentration in paddy soil

“…This may result from high sulfate concentrations in the soils since Syntrophobacteraceae have been suggested to be more common in presence of high sulfate content (Leloup et al 2007). The majority of uncultured dsrAB sequences detected here were related to environmental sequences retrieved from mudflat (Leloup et al 2006), everglades (Castro et al 2002), marine sediments (Jiang et al 2009), hot springs (Fishbain et al 2003), and paddy soil ).…”

Abundance and diversity of sulphate-reducing bacterioplankton in Lake Suigetsu, a meromictic lake in Fukui, Japan

“…Clone sequences in cluster G were closely related to an environmental sequence retrieved from a uranium mill tailing site (Chang et al 2001). Sequences from this cluster were also recovered from freshwater or brackish environments such as estuarine sediments (Bahr et al 2005, Kondo et al 2004, Leloup et al 2006) and a wetland (Castro et al 2002), but not marine environments (Dhillon et al 2003, Thomsen et al 2001). Members of the Desulfobulbaceae family can use alternative electron acceptors leading to sulphate and can disproportionate sulphur oxianions while Desulfobulbus is known to be able to grow by fermentation of lactate or ethanol and CO 2 without sulphate.…”

“…This cluster has been referred to as the UMTRA DSR cluster F (Chang et al 2001). The dominance of sequences related to this cluster was reported in ground water from a uranium mill tailing site (Chang et al 2001), a freshwater wetland (Castro et al 2002), acidic fens (Loy et al 2004) and a hydrothermal vent site (Dhillon et al 2003). This cluster is not related to any cultured SRB and its physiology is unknown.…”

Dynamics and Activity of Sulfate-Reducing Bacterial Populations in Paddy Soil under Subsurface Drainage: Case Study of Kamboinse in Burkina Faso

“…SRB also constitute a diverse group of prokaryotes with the common ability to metabolize oxidized sulfur compounds. They are universally distributed where sulfate reduction is the dominant biomineralization pathway as fens [10]- [12], estuary sediments [13]- [15]. Rice paddy fields also represent a freshwater environment in which sulfate reduction occurs and from which sulfate reducers have been isolated [6] [12] [16].…”