Daily thanatomicrobiome changes in soil as an approach of postmortem interval estimation: An ecological perspective

- This study depicts the thanatomicroniome succesional changes in soil on a daily basis.
- Microbial changes were monitored quantitatively and qualitatively along decomposition.
- Its potential use in forensic cases as a quantitative approach to estimate PMI.
- A drastic growth of Firmicutes is observed from bloat stage to advanced decay.
- Firmicutes growth curve is proposed to estimate PMI under Tennessee summer conditions.

Understanding human decomposition is critical for its use in postmortem interval (PMI) estimation, having a significant impact on forensic investigations. In recognition of the need to establish the scientific basis for PMI estimation, several studies on decomposition have been carried out in the last years. The aims of the present study were: (i) to identify soil microbiota communities involved in human decomposition through high-throughput sequencing (HTS) of DNA sequences from the different bacteria, (ii) to monitor quantitatively and qualitatively the decay of such signature species, and (iii) to describe succesional changes in bacterial populations from the early putrefaction state until skeletonization. Three donated individuals to the University of Tennessee FAC were studied. Soil samples around the body were taken from the placement of the donor until advanced decay/dry remains stage. Bacterial DNA extracts were obtained from the samples, HTS techniques were applied and bioinformatic data analysis was performed. The three cadavers showed similar overall successional changes. At the beginning of the decomposition process the soil microbiome consisted of diverse indigenous soil bacterial communities. As decomposition advanced, Firmicutes community abundance increased in the soil during the bloat stage. The growth curve of Firmicutes from human remains can be used to estimate time since death during Tennessee summer conditions.