Influence of Mass Burial of Animal Carcasses on the Types and Quantities of Microorganisms within a Burial Site

Abstract

Microbial communities were characterized through a depth of 10 m in and near an eight-year-old burial site that was implemented as a control measure for cases of chronic wasting disease among wild elk. Quantitative PCR based on the 16S rRNA-encoding gene showed that the burial trench had significantly (2 to 5 orders of magnitude) more bacterial 16S rRNA-encoding genes g-1 soil within and up to 2 m below the burial site compared to a nonburial control core sample at the same depths. Topsoil and depths below the burial site (>6 m) showed similar quantities of 16S rRNA genes for both cores. Furthermore, when microbial communities were examined by cpn60 universal target amplification and pyrosequencing, 5825 operational taxonomic units (OTU) were 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 that of the control core at all depths. Organisms associated with phosphate accumulation, nitrogen fixation, and ammonium oxidation were found in highest abundance near the surface of the burial core (up to 2.5 m), while organisms associated with ammonification were found at the burial depth, consistent with an increase in ammonium concentration in pore water. Sequences from organisms associated with dissimilatory metal reduction were concentrated just below the burial depth (4.5 to 5.5 m). Anaerobic microorganisms dominated the microbial community at the burial site (3.75 m). The approaches described in this study provided distinct sequences that can be used to develop molecular assays for organism tracking and overall fingerprinting of microbes associated with burial sites. These data can be helpful in site evaluation and may help in the selection of future burial sites.