Soil bacteria regulate wetland biogeochemical processes, yet little is known about controls over their distribution and abundance. Bacteria in North Carolina swamps and bogs differ greatly from Florida Everglades fens, where communities studied were unexpectedly similar along a nutrient enrichment gradient. Bacterial composition and diversity corresponded strongly with soil pH, land use, and restoration status, but less to nutrient concentrations, and not with wetland type or soil carbon. Surprisingly, wetland restoration decreased bacterial diversity, a response opposite to that in terrestrial ecosystems. Community level patterns were underlain by responses of a few taxa, especially the Acidobacteria and Proteobacteria, suggesting promise for bacterial indicators of restoration and trophic status.16S rDNA ͉ land use ͉ phylogenetic analysis ͉ restoration ͉ soil pH S oil bacterial communities play a critical role in regulating the cycling, retention, and release of major nutrients and soil carbon in freshwater wetlands, with demonstrably large effects on water quality (1) and global carbon cycling (2). However, little is known about the taxonomic composition of uncultured soil bacteria in freshwater wetlands relative to other ecosystems, despite the disproportionate influence of wetlands in controlling biogeochemical cycling at landscape scales (3). With a single exception in a Sphagnum bog (4), existing knowledge of bacterial communities in freshwater wetlands has been obtained using DNA fingerprinting (5, 6), group specific probes (7-9), or culture-based methods (8), which either have not identified bacterial taxonomic groups or do not adequately represent the vast diversity of uncultured soil bacteria (10). Furthermore, the environmental and anthropogenic factors controlling the distribution and abundance of bacterial groups in freshwater wetland soils are unknown.To predict the effects of ecosystem change on wetland functions, improved understanding of the ecological responses of uncultured bacterial communities to ecosystem alteration is needed to compliment existing knowledge of bacterial functional groups controlling specific biogeochemical processes. The importance of understanding controls over wetland bacterial communities is underscored by the unique nature of wetlands as transitional ecosystems, the role wetland bacteria play in regulating biogeochemical fluxes across different ecosystem types, and increasing efforts to restore the functionality of degraded wetlands subjected to land-use change (11). In our unique study, we demonstrate the spectrum of uncultured bacterial communities across a range of freshwater wetland types and quantify the influence of soil chemistry, land use, restoration, and soil nutrient concentrations on bacterial assemblages.Freshwater wetlands are transitional gradients between terrestrial and aquatic ecosystems, and thus may have environmental and anthropogenic controls over bacterial community structure similar to those of their neighboring ecosystems. Land use (12, 13) an...

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Veterinary antibiotics such as oxytetracycline (OTC) increasingly are found in the environment and often come into direct contact with soils via the release of animal wastes. Oxytetracycline is known to sorb strongly to soils by interaction with soil organic matter, clay minerals, and metal oxides. However, current knowledge of the influence of soil properties on OTC sorption is limited, as is our ability to predict OTC sorption to soils. This work was aimed at identifying properties that most influence the extent of OTC sorption in a suite of soils from the eastern United States representing a wide range in soil properties. Thirty soils were well characterized, an OTC soil-water distribution coefficient (Kd) was determined for each soil, and statistical analyses were employed to determine appropriate soil descriptors of OTC sorption. Soil texture, cation exchange capacity, and iron oxide content seemed to most influence the extent of OTC sorption in soils with organic carbon (OC) content between 0 and 4%. Thus, the knowledge of these three soil properties would be key to anticipating the extent of OTC sorption and gaining insight into OTC fate within a given soil system. Notably, OC content appeared to influence OTC sorption only in a soil with 9% OC.

Oxytetracycline (OTC) zwitterions sorbed to a greater extent than ciprofloxacin (CIP) zwitterions onto goethite and soils with moderate-to-low effective cation exchange capacities (ECEC < 10 cmol(c)/kg) because adjacent pairs of hydroxyl groups on the OTC molecule (absent in CIP) facilitated greater surface complexation to soil metal oxides and aluminosilicate edge sites. CIP sorbed to a higher extentthan OTC onto aluminosilicates and onto soils with "high" ECEC values (>10 cmol(c)/kg). The sorption of heterocyclic compounds structurally similar to CIP indicated that both positive charge localization on the cationic amine and the extent of charge delocalization to the heterocyclic ring influenced molecular orientation within the montmorillonite interlayers, van der Waals interactions, and the potential for sorption. The sorption of compounds structurally similar to OTC revealed that greater positive charge localization on the cationic amine facilitated sorption to montmorillonite, whereas ortho substituted anionic and cationic groups on a zwitterionic molecule resulted in unfavorable Coulombic interactions between the anionic moiety and the negatively charged surface and hindered sorption. Thus, greater CIP zwitterion sorption to aluminosilicates and "high" ECEC soils resulted from greater distance between the anionic and cationic groups, which maximized Coulombic attraction to the surface.

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