|MATHENY, TERRY - Retired ARS Employee|
Submitted to: The Open Microbiology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/8/2013
Publication Date: 6/28/2013
Citation: Ducey, T.F., Johnson, P.R., Shriner, A.D., Matheny, T.A., Hunt, P.G. 2013. Microbial community structure across a wastewater-impacted riparian buffer zone in the southeastern Coastal Plain. The Open Microbiology Journal. 7:99-117.
Interpretive Summary: Riparian buffer zones are used by farmers to protect nearby streams from pollutants generated during farming, in particular nitrogen. One particular biological process, denitrification, is responsible for turning agriculturally generated nitrogen waste into harmless nitrogen gas. While denitrification is often relied upon to help clean up areas near to agricultural systems, we do not have a full understanding of the microbial organisms responsible for this process. Therefore, we examined a riparian buffer zone system in the southeastern coastal plain which was adjacent to an agricultural field that received high levels of nitrogen addition. We used two methods to estimate the population diversity, and then determine the exact microbial organisms populating those soils. Our results demonstrated that no single microbial population was responsible for the denitrification measured in these soils. Rather, a large assemblage of Proteobacteria, most of which are able to grow with multiple energy sources, and a portion of which are capable of denitrification, are most likely responsible for this denitrification.
Technical Abstract: Riparian buffer zones are important for both natural and developed ecosystems throughout the world. However, their microbial community structure is only beginning to be defined and understood. Our objectives for this study were to characterize the microbial populations found in the soils of this riparian buffer zone, as well as to determine if these differences in microbial community structure could be linked to denitrification. We investigated the microbial community structure in a riparian buffer zone located downslope of a pasture irrigated with swine lagoon effluent. To achieve these aims we utilized two culture-independent, molecular methods: ribosomal intergenic spacer analysis (RISA), and 16S rDNA gene sequencing. RISA revealed a strong correlation between microbial diversity and depth to the water table. 16S rDNA clone libraries were generated from each of twelve sites across the riparian buffer. A total of 986 partial sequences were grouped into 654 operational taxonomic units (OTUs). The Proteobacteria were the dominant group (49.8%), with bacteria belonging to the different subclasses a- (19.72%) ß- (5.66%) d- (3.67%) '- (12.69%). The Acidobacteria were also well represented with 19.57% of the OTUs. Regression analyses revealed a statistically significant correlation between the phylum Proteobacteria and denitrification enzyme activity. This result indicates a link between microbial community composition and function across the riparian buffer zone.