Determination of Microbial Communities beneath Livestock Burial Sites

Abstract

A ten year old livestock burial site near Pierceland, Saskatchewan was continuously cored and analyzed for microbial communities at varying depths below the soil surface by molecular methods. 16S rRNA gene targets and quantitative PCR was utilized to provide a quantitative analysis of genomes per gram of soil and cpn-60 targets were used to amplify DNA for taxonomic profiling by 454 pyrosequencing. Quantification results demonstrate a three orders of magnitude greater difference in genomes at depths within and up to two meters below the burial trench as compared to a background core. Topsoil and depths below 6 meters show similar quantities of microbes for both the core through the burial trench and the background core. A total of 5905 OTUs was found at a variety of abundances in all of the 13 core samples that were analyzed. Taxonomic analysis indicated that the overall community composition changed considerably with increasing depth, and that the burial core community was distinct from the control core at the same depth. In the burial core, organisms that are associated with phosphate accumulation, nitrogen fixation, and ammonium oxidation were found in highest abundance near the surface (up to 2.5 m), while organisms associated with sulfate reduction were concentrated just below the burial depth (4.5-4.8 m). The microbial community at the burial site (3.75 m) was dominated by anaerobic microorganisms.