An Investigation into the Effects of Freezing on the Microbiome of Human Cadavers

Studies on the human microbiome for forensic applications, particularly regarding estimation of postmortem intervals, are on the rise. Many of these studies often involve cadavers which have been previously frozen and are then thawed prior to commencing research. While this cycle of freezing and thawing cadavers is common practice, its effect on the process of decomposition and the development of the (thanato)microbiome has not been extensively researched and documented. This study aims to understand how freezing cadavers can affect the microbiome as significant effects from freezing could skew experimental data and the resulting interpretation. To investigate the effects of freezing on the microbiome of cadavers, we collected swab samples from five anatomical locations of nine cadavers (oral, rectum, hand, foot, and neck). Cadavers were swabbed on arrival to the human taphonomy facility, and again after freezing at –20 °C and thawing. Samples are currently being processed by metabarcoding of the 16S rRNA region of the DNA extracts; however, results will be ready in time for the conference. This study will be essential for establishing and/or reviewing standard operating procedures on sampling human taphonomy facilities worldwide and will provide insight into the validity of using previously frozen cadavers in microbiome studies. The results may also provide useful information on microbial composition and abundance for forensic cases involving frozen bodies.