Since many studies have developed microbial succession-based models for the prediction of postmortem interval (PMI) in terrestrial systems but similar well-replicated long-term decomposition studies are lacking for aquatic systems, the current study sought to identify temporal changes in bacterial community structure associated with porcine skeletal remains (n = 198) for an extended period in a fresh-water lake.
Every ca. 250 ADD, one cage, containing five ribs and five scapulae, was removed from the lake for a total of 19 collections. Water was also sampled at each interval. Variable region 4 (V4) of 16S rDNA was amplified and sequenced for all collected samples using Illumina MiSeq FGx Sequencing platform; resulting data were analyzed with the mothur (v1.39.5) and R (v3.6.0). Bacterial communities associated with ribs differed significantly from those associated with scapulae. This difference was mainly attributed to Clostridia, Holophagae, and Spirochaete relative abundances. For each bone type, α-diversity increased with ADD; similarly, β-diversity bacterial community structure changed significantly with ADD and were explained using environmental parameters and inferred functional pathways. Models developed using 24 rib and 34 scapula family-level taxa allowed the prediction of PMSI with root mean square error of 522.97 ADD (~57 days) and 333.8 ADD (~37 days), respectively. (publisher abstract modified)
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