Since the placement of cadavers in shallow, clandestine graves may alter the microbial and geochemical composition of the underlying and adjacent soils, the current study used amplicon length heterogeneity-PCR (LH-PCR) to assess the microbial community changes in these soils.
Nine different grave sites were examined over a period of 16 weeks. The results indicated that measurable changes occurred in the soil bacterial community during the decomposition process. Amplicons corresponding to anaerobic bacteria not indigenous to the soil were found to produce differences among grave sites and control soils. Among the bacteria linked to these amplicons were those that are most often part of the commensal flora of the intestines, mouth, and skin. In addition, over the 16-week sampling interval, the level of indicator organisms (i.e., nitrogen fixing bacteria) dropped as the body decomposed; and after 4 weeks of environmental exposure, they began to increase again. Thus, differences in the abundance of nitrogen-fixing bacteria were also found to contribute to the variation between controls and grave soils. These results were verified using primers that specifically targeted the nifH gene coding for nitrogenase reductase. LH-PCR provides a fast, robust, and reproducible method to measure microbial changes in soil and could be used to determine potential cadaveric contact in an area. The results obtained with this method could ultimately provide leads to investigators in criminal or missing person scenarios and allow for further analysis using human specific DNA assays to establish the identity of the buried body. (publisher abstract modified)