A pilot study characterizing gravesoil bacterial communities a decade after swine decomposition

Area of Science:

• Ecology
• Microbiology
• Forensic Science

Background:

• Vertebrate decomposition releases fluids and microbes, impacting soil bacterial communities.
• These impacts, known as gravesoil effects, can persist for years but the duration is unclear.
• Understanding long-term decomposition effects is crucial for ecosystem studies and forensic science.

Purpose of the Study:

• To investigate the long-term effects of swine carcass decomposition on terrestrial soil bacterial communities over a 10-year period.
• To determine the temporal extent of soil bacterial community perturbations following decomposition.
• To identify bacterial genera useful for estimating time since death in forensic investigations.

Main Methods:

• 16S rRNA gene amplicon sequencing was used to analyze bacterial composition in soils associated with decomposing swine carcasses.
• A 10-year sampling period allowed for the analysis of bacterial diversity trends over time using repeated measures.
• Random forest regression models were employed to identify key bacterial genera for decomposition timepoint estimation.

Main Results:

• Soil bacterial diversity was significantly impacted by carcass decomposition, with effects localized to the area beneath the carcass.
• Maximum bacterial community dissimilarity was observed 12 months postmortem, followed by a gradual recovery.
• Ten bacterial genera were identified as important indicators for distinguishing decomposition timepoints, with four showing significant abundance shifts.

Conclusions:

• Swine carcass decomposition exerts a long-term influence on soil bacterial communities, persisting for up to a decade.
• The study provides a temporal characterization of these effects, expanding knowledge of decomposition's ecological role.
• Identified bacterial genera offer potential for improving postmortem interval estimation in forensic entomology.