Abstract
Advancements in molecular microbial ecology techniques have enabled researchers to study the complex interactions of epinecrobiome, necrobiome, and thanatomicrobiome communities during cadaver decomposition within novel forensic disciplines. This preliminary study tracks shifts in subsurface soil necrobiome as indicators of time-since-exhumation where whole juvenile Sus scrofa domesticus was used as the human cadaver proxy. Principal component analysis of DGGE-based diversity index (Shannon-Weiner, HꞋ; Simpson (D)) measurements showed more consistent delineation of pre- and post-exhumation periods of the fungal 18S gene with further clustering for days 270 and 300. More importantly, high-resolution metabarcoding of the 16S rRNA gene recorded temporal bacterial clock indicators at order and family levels. Specifically, Xanthomonadales (11.29%) and Xanthomonadaceae (4.27%), and Verrucomicrobiaceae (4.00%) were abundance-based season (spring–summer) and microbial clock indicators for post-burial interval (PBI) ≥ 150 days. Hydrogenophilales (7.13%) and Hydrogenophilaceae (7.56%), Clostridiales (4.57%) and Clostridiaceae_1 (3.13%), and Bacteroidales (3.33%) defined the impacts of 120 days since exhumation of Sus scrofa domesticus. They could, therefore, be tracked to identify grave emptying for the current soil type.
Highlights
Human cadavers and animal carrion are substantive energy resources with key roles in nutrient cycling
The applicability of a suite of techniques to study the postmortem microbiome and enhance postmortem interval (PMI) and time-since-burial/post-burial interval (PBI) determinations is evidenced with human cadavers [5] or mammalian taphonomic proxies such as pig (Sus scrofa domesticus; [6]), both the brown and laboratory rat (Rattus norvegicus Berkenhout; [7]), and mouse (Mus musculus Linnaeus; [8,9])
A pH of 7.83 was recorded for the S. s. domesticus mesocosm on day 60, which was in contrast to pH = 6.98 for the control. pH decreases occurred between days 120 and 270 to reach values around 6.09 in the decomposition mesocosm
Summary
Human cadavers and animal carrion are substantive energy resources with key roles in nutrient cycling. Their decomposition and subsequent influx of nutrients affect the surrounding environmental microbiota [1,2,3] and ecology directly; Carter et al. (2007) [4] designated this unique and dynamic ecosystem as a cadaver decomposition island (CDI). There remains a significant scope for knowledge development on the impacts of cadaver or mammalian surrogate decomposition on subsurface soil ecology. The detectable and measurable longevity of the biological CDI footprint can potentially provide further intelligence, generally, and at old crime scenes, in particular
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