Comparative soil bacterial metabarcoding after aboveground vs subsurface decomposition of Mus musculus. Mus musculus decomposition study

There is evidence that microorganisms are essential to carcass organic residue recycling with more knowledge required about the structure and dynamics of the associated microbial communities during decomposition. Decomposition is mostly affected by intrinsic factors related to the cadaver’s ante- and perimortem conditions and extrinsic biotic and abiotic parameters, which have a major effect on the decomposition rate. Outdoor microcosms and next-generation sequencing to species level were used in the current study to monitor Mus musculus decomposition aboveground and in the subsurface, and the subsequent effects on soil 16S rRNA bacterial communities at different depths below the decomposing animal model. Hill diversity metrics indicated seasonality and carrion deposition demonstrating therefore the potential for gravesoil discrimination. The bacterial community could distinguish control from experimental treatments during the first three months of the experiment while the main patterns detected afterward were related to seasonal weather variation. Methanosarcina spp, Rhodanobacter spp, Catellatospora spp, Devosia spp and Kaistobacter spp. correlated negatively with seasonal temperature variation at a 0 (zero) cm depth in the aboveground mice treatments while Devosia spp, Kaistobacter spp, Pedomicrobium spp and Rhodoplanes spp correlated positively with seasonal variation in the subsurface mice treatments. At 30 cm below the cadaver, Methanosarcina spp, Rhodanobacter spp and Devosia spp decreased in abundance at higher seasonal temperatures for the aboveground mice treatments. The effect of sampling on soil microbial community and elemental composition was investigated but did not show significant differences between the treatments sampled regularly and those sampled less frequently. Similarly, there was no significant difference between meteorological station records and in situ temperature readings, which suggests the feasibility of using temperature records from meteorological stations to estimate postmortem interval and decomposition stage. The trends in soil elemental composition, assessed by portable XRF, highlight the potential of using the influx of potassium into soil during the early putrefactive stages as an indicator of the phase of decomposition or the presence of a cadaver even if the body has been removed. The results of this study highlight the importance of combining different methods to inform investigations for PMI and clandestine grave locations. Notwithstanding this, adopting this approach to real-life investigations necessitates further research and case studies preferably using human remains, especially since differences exist in decomposition rate and processes between human and animal cadavers.