Forensic Microbiology of Human Cadavers in an Experimental Mass Grave

This project implements metabarcoding analyses on cadavers and soil samples in the first mass grave experiment conducted at Texas State University’s Forensic Anthropology Research Facility (FARF). The Mass Grave Project includes a mass grave with six donated human cadavers, a control mass grave without cadavers, three individual graves with cadavers, and one (empty) individual control grave, all buried in May 2021. The experiments will be monitored during 18 months, after which the graves will be excavated. Human microbiome samples were collected by swabbing five different locations on the body (hand, foot, neck, mouth and rectum) prior to freezing, after thawing/before burial, and further samples will be collected upon excavation. The aims of this study are to: 1) examine the effect freezing donated cadavers has on microbiome sampling in taphonomic studies; 2) examine microbial shifts associated with increasing PMIs in a mass grave, how they differ from single burials and how they migrate within different areas of the grave; and 3) compare the microbiome of different body sites before and after the decomposition, to identify good microbial indicators that could be used for estimating prolonged PMIs. Soil samples are being collected from the graves throughout the 18-month duration. Microbial DNA will be extracted using Qiagen DNeasy PowerSoil Pro Kit and will be analyzed via sequencing of the V4 region of the 16s rRNA gene using Illumina MiSeq platform. NGS data will be analyzed via R scripts normally used in metabarcoding ecology studies.