Bacterial populations associated with early-stage adipocere formation in lacustrine waters

Abstract

The preservation of soft tissue is a valuable evidence for forensic investigation as it may provide information about the cause and manner of death as well as the time since death. Adipocere forms from the conversion of triglycerides in the neutral fats into stable fatty acids producing a solid white product which aids tissue preservation. Adipocere will typically form in water-logged grave sites and aquatic environments. Documentation on the chemical and microbiological changes that cause adipocere formation in aquatic environments is scant and mostly based on observational case reports. The aim of this study was to monitor the early adipocere formation in lacustrine waters to investigate the effect of aquatic bacteria on adipocere formation. Tissue samples from pork (Sus scrofa domesticus) belly were submerged in water samples from Lake Ontario and deionised water (control). Bacteria samples from both water and tissue were harvested. Changes in the fatty acid composition of the tissue were determined using gas chromatography-mass spectrometry. Early-stage adipocere formation was confirmed on porcine tissue submerged in lake water but was not identified on porcine tissue submerged in deionised water. Adipocere formation required an abundance of gram-positive bacteria during the early postmortem period to assist in lipolysing the triglycerides into free fatty acids. Formation of adipocere in the lake water resulted in a decrease in bacterial concentrations in the tissue over time.